icinga2/doc/03-monitoring-basics.md

Monitoring Basics

This part of the Icinga 2 documentation provides an overview of all the basic monitoring concepts you need to know to run Icinga 2. Keep in mind these examples are made with a Linux server. If you are using Windows, you will need to change the services accordingly. See the ITL reference for further information.

Attribute Value Types

The Icinga 2 configuration uses different value types for attributes.

Type	Example
Number	5
Duration	1m
String	"These are notes"
Boolean	true
Array	[ "value1", "value2" ]
Dictionary	{ "key1" = "value1", "key2" = false }

It is important to use the correct value type for object attributes as otherwise the configuration validation will fail.

Hosts and Services

Icinga 2 can be used to monitor the availability of hosts and services. Hosts and services can be virtually anything which can be checked in some way:

• Network services (HTTP, SMTP, SNMP, SSH, etc.)
• Printers
• Switches or routers
• Temperature sensors
• Other local or network-accessible services

Host objects provide a mechanism to group services that are running on the same physical device.

Here is an example of a host object which defines two child services:

object Host "my-server1" {
  address = "10.0.0.1"
  check_command = "hostalive"
}

object Service "ping4" {
  host_name = "my-server1"
  check_command = "ping4"
}

object Service "http" {
  host_name = "my-server1"
  check_command = "http"
}

The example creates two services ping4 and http which belong to the host my-server1.

It also specifies that the host should perform its own check using the hostalive check command.

The address attribute is used by check commands to determine which network address is associated with the host object.

Details on troubleshooting check problems can be found here.

Host States

Hosts can be in any one of the following states:

Name	Description
UP	The host is available.
DOWN	The host is unavailable.

Service States

Services can be in any one of the following states:

Name	Description
OK	The service is working properly.
WARNING	The service is experiencing some problems but is still considered to be in working condition.
CRITICAL	The check successfully determined that the service is in a critical state.
UNKNOWN	The check could not determine the service's state.

Check Result State Mapping

Check plugins return with an exit code which is converted into a state number. Services map the states directly while hosts will treat 0 or 1 as UP for example.

Value	Host State	Service State
0	Up	OK
1	Up	Warning
2	Down	Critical
3	Down	Unknown

Hard and Soft States

When detecting a problem with a host/service, Icinga re-checks the object a number of times (based on the max_check_attempts and retry_interval settings) before sending notifications. This ensures that no unnecessary notifications are sent for transient failures. During this time the object is in a SOFT state.

After all re-checks have been executed and the object is still in a non-OK state, the host/service switches to a HARD state and notifications are sent.

Name	Description
HARD	The host/service's state hasn't recently changed. check_interval applies here.
SOFT	The host/service has recently changed state and is being re-checked with retry_interval.

Host and Service Checks

Hosts and services determine their state by running checks in a regular interval.

object Host "router" {
  check_command = "hostalive"
  address = "10.0.0.1"
}

The hostalive command is one of several built-in check commands. It sends ICMP echo requests to the IP address specified in the address attribute to determine whether a host is online.

Tip

hostalive is the same as ping but with different default thresholds. Both use the ping CLI command to execute sequential checks.

If you need faster ICMP checks, look into the icmp CheckCommand.

A number of other built-in check commands are also available. In addition to these commands the next few chapters will explain in detail how to set up your own check commands.

Host Check Alternatives

If the host is not reachable with ICMP, HTTP, etc. you can also use the dummy CheckCommand to set a default state.

object Host "dummy-host" {
  check_command = "dummy"
  vars.dummy_state = 0 //Up
  vars.dummy_text = "Everything OK."
}

This method is also used when you send in external check results.

A more advanced technique is to calculate an overall state based on all services. This is described here.

Templates

Templates may be used to apply a set of identical attributes to more than one object:

template Service "generic-service" {
  max_check_attempts = 3
  check_interval = 5m
  retry_interval = 1m
  enable_perfdata = true
}

apply Service "ping4" {
  import "generic-service"

  check_command = "ping4"

  assign where host.address
}

apply Service "ping6" {
  import "generic-service"

  check_command = "ping6"

  assign where host.address6
}

In this example the ping4 and ping6 services inherit properties from the template generic-service.

Objects as well as templates themselves can import an arbitrary number of other templates. Attributes inherited from a template can be overridden in the object if necessary.

You can also import existing non-template objects.

Note

Templates and objects share the same namespace, i.e. you can't define a template that has the same name like an object.

Multiple Templates

The following example uses custom variables which are provided in each template. The web-server template is used as the base template for any host providing web services. In addition to that it specifies the custom variable webserver_type, e.g. apache. Since this template is also the base template, we import the generic-host template here. This provides the check_command attribute by default and we don't need to set it anywhere later on.

template Host "web-server" {
  import "generic-host"
  vars = {
    webserver_type = "apache"
  }
}

The wp-server host template specifies a Wordpress instance and sets the application_type custom variable. Please note the += operator which adds dictionary items, but does not override any previous vars attribute.

template Host "wp-server" {
  vars += {
    application_type = "wordpress"
  }
}

The final host object imports both templates. The order is important here: First the base template web-server is added to the object, then additional attributes are imported from the wp-server object.

object Host "wp.example.com" {
  import "web-server"
  import "wp-server"

  address = "192.168.56.200"
}

If you want to override specific attributes inherited from templates, you can specify them on the host object.

object Host "wp1.example.com" {
  import "web-server"
  import "wp-server"

  vars.webserver_type = "nginx" //overrides attribute from base template

  address = "192.168.56.201"
}

Custom Variables

In addition to built-in object attributes you can define your own custom attributes inside the vars attribute.

Tip

This is called custom variables throughout the documentation, backends and web interfaces.

Older documentation versions referred to this as custom attribute.

The following example specifies the key ssh_port as custom variable and assigns an integer value.

object Host "localhost" {
  check_command = "ssh"
  vars.ssh_port = 2222
}

vars is a dictionary where you can set specific keys to values. The example above uses the shorter indexer syntax.

An alternative representation can be written like this:

  vars = {
    ssh_port = 2222
  }

or

  vars["ssh_port"] = 2222

Custom Variable Values

Valid values for custom variables include:

• Strings, numbers and booleans
• Arrays and dictionaries
• Functions

You can also define nested values such as dictionaries in dictionaries.

This example defines the custom variable disks as dictionary. The first key is set to disk / is itself set to a dictionary with one key-value pair.

  vars.disks["disk /"] = {
    disk_partitions = "/"
  }

This can be written as resolved structure like this:

  vars = {
    disks = {
      "disk /" = {
        disk_partitions = "/"
      }
    }
  }

Keep this in mind when trying to access specific sub-keys in apply rules or functions.

Another example which is shown in the example configuration:

  vars.notification["mail"] = {
    groups = [ "icingaadmins" ]
  }

This defines the notification custom variable as dictionary with the key mail. Its value is a dictionary with the key groups which itself has an array as value. Note: This array is the exact same as the user_groups attribute for notification apply rules expects.

  vars.notification = {
    mail = {
      groups = [
        "icingaadmins"
      ]
    }
  }

Functions as Custom Variables

Icinga 2 lets you specify functions for custom variables. The special case here is that whenever Icinga 2 needs the value for such a custom variable it runs the function and uses whatever value the function returns:

object CheckCommand "random-value" {
  command = [ PluginDir + "/check_dummy", "0", "$text$" ]

  vars.text = {{ Math.random() * 100 }}
}

This example uses the abbreviated lambda syntax.

These functions have access to a number of variables:

Variable	Description
user	The User object (for notifications).
service	The Service object (for service checks/notifications/event handlers).
host	The Host object.
command	The command object (e.g. a CheckCommand object for checks).

Here's an example:

vars.text = {{ host.check_interval }}

In addition to these variables the macro function can be used to retrieve the value of arbitrary macro expressions:

vars.text = {{
  if (macro("$address$") == "127.0.0.1") {
    log("Running a check for localhost!")
  }

  return "Some text"
}}

The resolve_arguments function can be used to resolve a command and its arguments much in the same fashion Icinga does this for the command and arguments attributes for commands. The by_ssh command uses this functionality to let users specify a command and arguments that should be executed via SSH:

arguments = {
  "-C" = {{
    var command = macro("$by_ssh_command$")
    var arguments = macro("$by_ssh_arguments$")

    if (typeof(command) == String && !arguments) {
      return command
    }

    var escaped_args = []
    for (arg in resolve_arguments(command, arguments)) {
      escaped_args.add(escape_shell_arg(arg))
    }
    return escaped_args.join(" ")
  }}
  ...
}

Accessing object attributes at runtime inside these functions is described in the advanced topics chapter.

Runtime Macros

Macros can be used to access other objects' attributes and custom variables at runtime. For example they are used in command definitions to figure out which IP address a check should be run against:

object CheckCommand "my-ping" {
  command = [ PluginDir + "/check_ping" ]

  arguments = {
    "-H" = "$ping_address$"
    "-w" = "$ping_wrta$,$ping_wpl$%"
    "-c" = "$ping_crta$,$ping_cpl$%"
    "-p" = "$ping_packets$"
  }

  // Resolve from a host attribute, or custom variable.
  vars.ping_address = "$address$"

  // Default values
  vars.ping_wrta = 100
  vars.ping_wpl = 5

  vars.ping_crta = 250
  vars.ping_cpl = 10

  vars.ping_packets = 5
}

object Host "router" {
  check_command = "my-ping"
  address = "10.0.0.1"
}

In this example we are using the $address$ macro to refer to the host's address attribute.

We can also directly refer to custom variables, e.g. by using $ping_wrta$. Icinga automatically tries to find the closest match for the attribute you specified. The exact rules for this are explained in the next section.

Note

When using the $ sign as single character you must escape it with an additional dollar character ($$).

Evaluation Order

When executing commands Icinga 2 checks the following objects in this order to look up macros and their respective values:

1. User object (only for notifications)
2. Service object
3. Host object
4. Command object
5. Global custom variables in the Vars constant

This execution order allows you to define default values for custom variables in your command objects.

Here's how you can override the custom variable ping_packets from the previous example:

object Service "ping" {
  host_name = "localhost"
  check_command = "my-ping"

  vars.ping_packets = 10 // Overrides the default value of 5 given in the command
}

If a custom variable isn't defined anywhere, an empty value is used and a warning is written to the Icinga 2 log.

You can also directly refer to a specific attribute -- thereby ignoring these evaluation rules -- by specifying the full attribute name:

$service.vars.ping_wrta$

This retrieves the value of the ping_wrta custom variable for the service. This returns an empty value if the service does not have such a custom variable no matter whether another object such as the host has this attribute.

Host Runtime Macros

The following host custom variables are available in all commands that are executed for hosts or services:

Name	Description
host.name	The name of the host object.
host.display_name	The value of the display_name attribute.
host.state	The host's current state. Can be one of UNREACHABLE, UP and DOWN.
host.state_id	The host's current state. Can be one of 0 (up), 1 (down) and 2 (unreachable).
host.state_type	The host's current state type. Can be one of SOFT and HARD.
host.check_attempt	The current check attempt number.
host.max_check_attempts	The maximum number of checks which are executed before changing to a hard state.
host.last_state	The host's previous state. Can be one of UNREACHABLE, UP and DOWN.
host.last_state_id	The host's previous state. Can be one of 0 (up), 1 (down) and 2 (unreachable).
host.last_state_type	The host's previous state type. Can be one of SOFT and HARD.
host.last_state_change	The last state change's timestamp.
host.downtime_depth	The number of active downtimes.
host.duration_sec	The time since the last state change.
host.latency	The host's check latency.
host.execution_time	The host's check execution time.
host.output	The last check's output.
host.perfdata	The last check's performance data.
host.last_check	The timestamp when the last check was executed.
host.check_source	The monitoring instance that performed the last check.
host.num_services	Number of services associated with the host.
host.num_services_ok	Number of services associated with the host which are in an OK state.
host.num_services_warning	Number of services associated with the host which are in a WARNING state.
host.num_services_unknown	Number of services associated with the host which are in an UNKNOWN state.
host.num_services_critical	Number of services associated with the host which are in a CRITICAL state.

In addition to these specific runtime macros host object attributes can be accessed too.

Service Runtime Macros

The following service macros are available in all commands that are executed for services:

Name	Description
service.name	The short name of the service object.
service.display_name	The value of the display_name attribute.
service.check_command	The short name of the command along with any arguments to be used for the check.
service.state	The service's current state. Can be one of OK, WARNING, CRITICAL and UNKNOWN.
service.state_id	The service's current state. Can be one of 0 (ok), 1 (warning), 2 (critical) and 3 (unknown).
service.state_type	The service's current state type. Can be one of SOFT and HARD.
service.check_attempt	The current check attempt number.
service.max_check_attempts	The maximum number of checks which are executed before changing to a hard state.
service.last_state	The service's previous state. Can be one of OK, WARNING, CRITICAL and UNKNOWN.
service.last_state_id	The service's previous state. Can be one of 0 (ok), 1 (warning), 2 (critical) and 3 (unknown).
service.last_state_type	The service's previous state type. Can be one of SOFT and HARD.
service.last_state_change	The last state change's timestamp.
service.downtime_depth	The number of active downtimes.
service.duration_sec	The time since the last state change.
service.latency	The service's check latency.
service.execution_time	The service's check execution time.
service.output	The last check's output.
service.perfdata	The last check's performance data.
service.last_check	The timestamp when the last check was executed.
service.check_source	The monitoring instance that performed the last check.

In addition to these specific runtime macros service object attributes can be accessed too.

Command Runtime Macros

The following custom variables are available in all commands:

Name	Description
command.name	The name of the command object.

User Runtime Macros

The following custom variables are available in all commands that are executed for users:

Name	Description
user.name	The name of the user object.
user.display_name	The value of the display_name attribute.

In addition to these specific runtime macros user object attributes can be accessed too.

Notification Runtime Macros

Name	Description
notification.type	The type of the notification.
notification.author	The author of the notification comment if existing.
notification.comment	The comment of the notification if existing.

In addition to these specific runtime macros notification object attributes can be accessed too.

Global Runtime Macros

The following macros are available in all executed commands:

Name	Description
icinga.timet	Current UNIX timestamp.
icinga.long_date_time	Current date and time including timezone information. Example: 2014-01-03 11:23:08 +0000
icinga.short_date_time	Current date and time. Example: 2014-01-03 11:23:08
icinga.date	Current date. Example: 2014-01-03
icinga.time	Current time including timezone information. Example: 11:23:08 +0000
icinga.uptime	Current uptime of the Icinga 2 process.

The following macros provide global statistics:

Name	Description
icinga.num_services_ok	Current number of services in state 'OK'.
icinga.num_services_warning	Current number of services in state 'Warning'.
icinga.num_services_critical	Current number of services in state 'Critical'.
icinga.num_services_unknown	Current number of services in state 'Unknown'.
icinga.num_services_pending	Current number of pending services.
icinga.num_services_unreachable	Current number of unreachable services.
icinga.num_services_flapping	Current number of flapping services.
icinga.num_services_in_downtime	Current number of services in downtime.
icinga.num_services_acknowledged	Current number of acknowledged service problems.
icinga.num_hosts_up	Current number of hosts in state 'Up'.
icinga.num_hosts_down	Current number of hosts in state 'Down'.
icinga.num_hosts_unreachable	Current number of unreachable hosts.
icinga.num_hosts_pending	Current number of pending hosts.
icinga.num_hosts_flapping	Current number of flapping hosts.
icinga.num_hosts_in_downtime	Current number of hosts in downtime.
icinga.num_hosts_acknowledged	Current number of acknowledged host problems.

Environment Variable Runtime Macros

All environment variables of the Icinga process are available as runtime macros named env.<env var name>. E.g. $env.ProgramFiles$ for ProgramFiles which is especially useful on Windows. In contrast to the other runtime macros env vars require the env. prefix.

Apply Rules

Several object types require an object relation, e.g. Service, Notification, Dependency, ScheduledDowntime objects. The object relations are documented in the linked chapters.

If you for example create a service object you have to specify the host_name attribute and reference an existing host attribute.

object Service "ping4" {
  check_command = "ping4"
  host_name = "icinga2-agent1.localdomain"
}

This isn't comfortable when managing a huge set of configuration objects which could match on a common pattern.

Instead you want to use apply rules.

If you want basic monitoring for all your hosts, add a ping4 service apply rule for all hosts which have the address attribute specified. Just one rule for 1000 hosts instead of 1000 service objects. Apply rules will automatically generate them for you.

apply Service "ping4" {
  check_command = "ping4"
  assign where host.address
}

More explanations on assign where expressions can be found here.

Apply Rules: Prerequisites

Before you start with apply rules keep the following in mind:

• Define the best match.
  • A set of unique custom variables for these hosts/services?
  • Or group memberships, e.g. a host being a member of a hostgroup which should have a service set?
  • A generic pattern match on the host/service name?
  • Multiple expressions combined with && or || operators
• All expressions must return a boolean value (an empty string is equal to false e.g.)

More specific object type requirements are described in these chapters:

• Apply services to hosts
• Apply notifications to hosts and services
• Apply dependencies to hosts and services
• Apply scheduled downtimes to hosts and services

Apply Rules: Usage Examples

You can set/override object attributes in apply rules using the respectively available objects in that scope (host and/or service objects).

vars.application_type = host.vars.application_type

Custom variables can also store nested dictionaries and arrays. That way you can use them for not only matching for their existence or values in apply expressions, but also assign ("inherit") their values into the generated objected from apply rules.

Remember the examples shown for custom variable values:

  vars.notification["mail"] = {
    groups = [ "icingaadmins" ]
  }

You can do two things here:

• Check for the existence of the notification custom variable and its nested dictionary key mail. If this is boolean true, the notification object will be generated.
• Assign the value of the groups key to the user_groups attribute.

apply Notification "mail-icingaadmin" to Host {
  [...]

  user_groups = host.vars.notification.mail.groups

  assign where host.vars.notification.mail
}

A more advanced example is to use apply rules with for loops on arrays or dictionaries provided by custom atttributes or groups.

Remember the examples shown for custom variable values:

  vars.disks["disk /"] = {
    disk_partitions = "/"
  }

You can iterate over all dictionary keys defined in disks. You can optionally use the value to specify additional object attributes.

apply Service for (disk => config in host.vars.disks) {
  [...]

  vars.disk_partitions = config.disk_partitions
}

Please read the apply for chapter for more specific insights.

Tip

Building configuration in that dynamic way requires detailed information of the generated objects. Use the object list CLI command after successful configuration validation.

Apply Rules Expressions

You can use simple or advanced combinations of apply rule expressions. Each expression must evaluate into the boolean true value. An empty string will be for instance interpreted as false. In a similar fashion undefined attributes will return false.

Returns false:

assign where host.vars.attribute_does_not_exist

Multiple assign where condition rows are evaluated as OR condition.

You can combine multiple expressions for matching only a subset of objects. In some cases, you want to be able to add more than one assign/ignore where expression which matches a specific condition. To achieve this you can use the logical and and or operators.

Apply Rules Expressions Examples

Assign a service to a specific host in a host group array using the in operator:

assign where "hostgroup-dev" in host.groups

Assign an object when a custom variable is equal to a value:

assign where host.vars.application_type == "database"

assign where service.vars.sms_notify == true

Assign an object if a dictionary contains a given key:

assign where host.vars.app_dict.contains("app")

Match the host name by either using a case insensitive match:

assign where match("webserver*", host.name)

Match the host name by using a regular expression. Please note the escaped backslash character:

assign where regex("^webserver-[\\d+]", host.name)

Match all *mysql* patterns in the host name and (&&) custom variable prod_mysql_db matches the db-* pattern. All hosts with the custom variable test_server set to true should be ignored, or any host name ending with *internal pattern.

object HostGroup "mysql-server" {
  display_name = "MySQL Server"

  assign where match("*mysql*", host.name) && match("db-*", host.vars.prod_mysql_db)
  ignore where host.vars.test_server == true
  ignore where match("*internal", host.name)
}

Similar example for advanced notification apply rule filters: If the service attribute notes matches the has gold support 24x7 string AND one of the two condition passes, either the customer host custom variable is set to customer-xy OR the host custom variable always_notify is set to true.

The notification is ignored for services whose host name ends with *internal OR the priority custom variable is less than 2.

template Notification "cust-xy-notification" {
  users = [ "noc-xy", "mgmt-xy" ]
  command = "mail-service-notification"
}

apply Notification "notify-cust-xy-mysql" to Service {
  import "cust-xy-notification"

  assign where match("*has gold support 24x7*", service.notes) && (host.vars.customer == "customer-xy" || host.vars.always_notify == true)
  ignore where match("*internal", host.name) || (service.vars.priority < 2 && host.vars.is_clustered == true)
}

More advanced examples are covered here.

Apply Services to Hosts

The sample configuration already includes a detailed example in hosts.conf and services.conf for this use case.

The example for ssh applies a service object to all hosts with the address attribute being defined and the custom variable os set to the string Linux in vars.

apply Service "ssh" {
  import "generic-service"

  check_command = "ssh"

  assign where host.address && host.vars.os == "Linux"
}

Other detailed examples are used in their respective chapters, for example apply services with custom command arguments.

Apply Notifications to Hosts and Services

Notifications are applied to specific targets (Host or Service) and work in a similar manner:

apply Notification "mail-noc" to Service {
  import "mail-service-notification"

  user_groups = [ "noc" ]

  assign where host.vars.notification.mail
}

In this example the mail-noc notification will be created as object for all services having the notification.mail custom variable defined. The notification command is set to mail-service-notification and all members of the user group noc will get notified.

It is also possible to generally apply a notification template and dynamically overwrite values from the template by checking for custom variables. This can be achieved by using conditional statements:

apply Notification "host-mail-noc" to Host {
  import "mail-host-notification"

  // replace interval inherited from `mail-host-notification` template with new notfication interval set by a host custom variable
  if (host.vars.notification_interval) {
    interval = host.vars.notification_interval
  }

  // same with notification period
  if (host.vars.notification_period) {
    period = host.vars.notification_period
  }

  // Send SMS instead of email if the host's custom variable `notification_type` is set to `sms`
  if (host.vars.notification_type == "sms") {
    command = "sms-host-notification"
  } else {
    command = "mail-host-notification"
  }

  user_groups = [ "noc" ]

  assign where host.address
}

In the example above the notification template mail-host-notification contains all relevant notification settings. The apply rule is applied on all host objects where the host.address is defined.

If the host object has a specific custom variable set, its value is inherited into the local notification object scope, e.g. host.vars.notification_interval, host.vars.notification_period and host.vars.notification_type. This overwrites attributes already specified in the imported mail-host-notification template.

The corresponding host object could look like this:

object Host "host1" {
  import "host-linux-prod"
  display_name = "host1"
  address = "192.168.1.50"
  vars.notification_interval = 1h
  vars.notification_period = "24x7"
  vars.notification_type = "sms"
}

Apply Dependencies to Hosts and Services

Detailed examples can be found in the dependencies chapter.

Apply Recurring Downtimes to Hosts and Services

The sample configuration includes an example in downtimes.conf.

Detailed examples can be found in the recurring downtimes chapter.

Using Apply For Rules

Next to the standard way of using apply rules there is the requirement of applying objects based on a set (array or dictionary) using apply for expressions.

The sample configuration already includes a detailed example in hosts.conf and services.conf for this use case.

Take the following example: A host provides the snmp oids for different service check types. This could look like the following example:

object Host "router-v6" {
  check_command = "hostalive"
  address6 = "2001:db8:1234::42"

  vars.oids["if01"] = "1.1.1.1.1"
  vars.oids["temp"] = "1.1.1.1.2"
  vars.oids["bgp"] = "1.1.1.1.5"
}

The idea is to create service objects for if01 and temp but not bgp. The oid value should also be used as service custom variable snmp_oid. This is the command argument required by the snmp check command. The service's display_name should be set to the identifier inside the dictionary, e.g. if01.

apply Service for (identifier => oid in host.vars.oids) {
  check_command = "snmp"
  display_name = identifier
  vars.snmp_oid = oid

  ignore where identifier == "bgp" //don't generate service for bgp checks
}

Icinga 2 evaluates the apply for rule for all objects with the custom variable oids set. It iterates over all dictionary items inside the for loop and evaluates the assign/ignore where expressions. You can access the loop variable in these expressions, e.g. to ignore specific values.

In this example the bgp identifier is ignored. This avoids to generate unwanted services. A different approach would be to match the oid value with a regex/wildcard match pattern for example.

  ignore where regex("^\d.\d.\d.\d.5$", oid)

Note

You don't need an assign where expression which checks for the existence of the oids custom variable.

This method saves you from creating multiple apply rules. It also moves the attribute specification logic from the service to the host.

Apply For and Custom Variable Override

Imagine a different more advanced example: You are monitoring your network device (host) with many interfaces (services). The following requirements/problems apply:

• Each interface service should be named with a prefix and a name defined in your host object (which could be generated from your CMDB, etc.)
• Each interface has its own VLAN tag
• Some interfaces have QoS enabled
• Additional attributes such as display_name or notes, notes_url and action_url must be dynamically generated.

Tip

Define the SNMP community as global constant in your constants.conf file.

const IftrafficSnmpCommunity = "public"

Define the interfaces custom variable on the cisco-catalyst-6509-34 host object and add three example interfaces as dictionary keys.

Specify additional attributes inside the nested dictionary as learned with custom variable values:

object Host "cisco-catalyst-6509-34" {
  import "generic-host"
  display_name = "Catalyst 6509 #34 VIE21"
  address = "127.0.1.4"

  /* "GigabitEthernet0/2" is the interface name,
   * and key name in service apply for later on
   */
  vars.interfaces["GigabitEthernet0/2"] = {
     /* define all custom variables with the
      * same name required for command parameters/arguments
      * in service apply (look into your CheckCommand definition)
      */
     iftraffic_units = "g"
     iftraffic_community = IftrafficSnmpCommunity
     iftraffic_bandwidth = 1
     vlan = "internal"
     qos = "disabled"
  }
  vars.interfaces["GigabitEthernet0/4"] = {
     iftraffic_units = "g"
     //iftraffic_community = IftrafficSnmpCommunity
     iftraffic_bandwidth = 1
     vlan = "remote"
     qos = "enabled"
  }
  vars.interfaces["MgmtInterface1"] = {
     iftraffic_community = IftrafficSnmpCommunity
     vlan = "mgmt"
     interface_address = "127.99.0.100" #special management ip
  }
}

Start with the apply for definition and iterate over host.vars.interfaces. This is a dictionary and should use the variables interface_name as key and interface_config as value for each generated object scope.

"if-" specifies the object name prefix for each service which results in if-<interface_name> for each iteration.

/* loop over the host.vars.interfaces dictionary
 * for (key => value in dict) means `interface_name` as key
 * and `interface_config` as value. Access config attributes
 * with the indexer (`.`) character.
 */
apply Service "if-" for (interface_name => interface_config in host.vars.interfaces) {

Import the generic-service template, assign the iftraffic check_command. Use the dictionary key interface_name to set a proper display_name string for external interfaces.

  import "generic-service"
  check_command = "iftraffic"
  display_name = "IF-" + interface_name

The interface_name key's value is the same string used as command parameter for iftraffic:

  /* use the key as command argument (no duplication of values in host.vars.interfaces) */
  vars.iftraffic_interface = interface_name

Remember that interface_config is a nested dictionary. In the first iteration it looks like this:

interface_config = {
  iftraffic_units = "g"
  iftraffic_community = IftrafficSnmpCommunity
  iftraffic_bandwidth = 1
  vlan = "internal"
  qos = "disabled"
}

Access the dictionary keys with the indexer syntax and assign them to custom variables used as command parameters for the iftraffic check command.

  /* map the custom variables as command arguments */
  vars.iftraffic_units = interface_config.iftraffic_units
  vars.iftraffic_community = interface_config.iftraffic_community

If you just want to inherit all attributes specified inside the interface_config dictionary, add it to the generated service custom variables like this:

  /* the above can be achieved in a shorter fashion if the names inside host.vars.interfaces
   * are the _exact_ same as required as command parameter by the check command
   * definition.
   */
  vars += interface_config

If the user did not specify default values for required service custom variables, add them here. This also helps to avoid unwanted configuration validation errors or runtime failures. Please read more about conditional statements here.

  /* set a default value for units and bandwidth */
  if (interface_config.iftraffic_units == "") {
    vars.iftraffic_units = "m"
  }
  if (interface_config.iftraffic_bandwidth == "") {
    vars.iftraffic_bandwidth = 1
  }
  if (interface_config.vlan == "") {
    vars.vlan = "not set"
  }
  if (interface_config.qos == "") {
    vars.qos = "not set"
  }

If the host object did not specify a custom SNMP community, set a default value specified by the global constant IftrafficSnmpCommunity.

  /* set the global constant if not explicitely
   * not provided by the `interfaces` dictionary on the host
   */
  if (len(interface_config.iftraffic_community) == 0 || len(vars.iftraffic_community) == 0) {
    vars.iftraffic_community = IftrafficSnmpCommunity
  }

Use the provided values to calculate more object attributes which can be e.g. seen in external interfaces.

  /* Calculate some additional object attributes after populating the `vars` dictionary */
  notes = "Interface check for " + interface_name + " (units: '" + interface_config.iftraffic_units + "') in VLAN '" + vars.vlan + "' with ' QoS '" + vars.qos + "'"
  notes_url = "https://foreman.company.com/hosts/" + host.name
  action_url = "https://snmp.checker.company.com/" + host.name + "/if-" + interface_name
}

Tip

Building configuration in that dynamic way requires detailed information of the generated objects. Use the object list CLI command after successful configuration validation.

Verify that the apply-for-rule successfully created the service objects with the inherited custom variables:

# icinga2 daemon -C
# icinga2 object list --type Service --name *catalyst*

Object 'cisco-catalyst-6509-34!if-GigabitEthernet0/2' of type 'Service':
......
  * vars
    % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 59:3-59:26
    * iftraffic_bandwidth = 1
    * iftraffic_community = "public"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 53:3-53:65
    * iftraffic_interface = "GigabitEthernet0/2"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 49:3-49:43
    * iftraffic_units = "g"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 52:3-52:57
    * qos = "disabled"
    * vlan = "internal"


Object 'cisco-catalyst-6509-34!if-GigabitEthernet0/4' of type 'Service':
...
  * vars
    % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 59:3-59:26
    * iftraffic_bandwidth = 1
    * iftraffic_community = "public"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 53:3-53:65
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 79:5-79:53
    * iftraffic_interface = "GigabitEthernet0/4"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 49:3-49:43
    * iftraffic_units = "g"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 52:3-52:57
    * qos = "enabled"
    * vlan = "remote"

Object 'cisco-catalyst-6509-34!if-MgmtInterface1' of type 'Service':
...
  * vars
    % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 59:3-59:26
    * iftraffic_bandwidth = 1
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 66:5-66:32
    * iftraffic_community = "public"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 53:3-53:65
    * iftraffic_interface = "MgmtInterface1"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 49:3-49:43
    * iftraffic_units = "m"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 52:3-52:57
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 63:5-63:30
    * interface_address = "127.99.0.100"
    * qos = "not set"
      % = modified in '/etc/icinga2/conf.d/iftraffic.conf', lines 72:5-72:24
    * vlan = "mgmt"

Use Object Attributes in Apply Rules

Since apply rules are evaluated after the generic objects, you can reference existing host and/or service object attributes as values for any object attribute specified in that apply rule.

object Host "opennebula-host" {
  import "generic-host"
  address = "10.1.1.2"

  vars.hosting["cust1"] = {
    http_uri = "/shop"
    customer_name = "Customer 1"
    customer_id = "7568"
    support_contract = "gold"
  }
  vars.hosting["cust2"] = {
    http_uri = "/"
    customer_name = "Customer 2"
    customer_id = "7569"
    support_contract = "silver"
  }
}

hosting is a custom variable with the Dictionary value type. This is mandatory to iterate with the key => value notation in the below apply for rule.

apply Service for (customer => config in host.vars.hosting) {
  import "generic-service"
  check_command = "ping4"

  vars.qos = "disabled"

  vars += config

  vars.http_uri = "/" + customer + "/" + config.http_uri

  display_name = "Shop Check for " + vars.customer_name + "-" + vars.customer_id

  notes = "Support contract: " + vars.support_contract + " for Customer " + vars.customer_name + " (" + vars.customer_id + ")."

  notes_url = "https://foreman.company.com/hosts/" + host.name
  action_url = "https://snmp.checker.company.com/" + host.name + "/" + vars.customer_id
}

Each loop iteration has different values for customer and config` in the local scope.

customer = "cust 1"
config = {
  http_uri = "/shop"
  customer_name = "Customer 1"
  customer_id = "7568"
  support_contract = "gold"
}

customer = "cust2"
config = {
  http_uri = "/"
  customer_name = "Customer 2"
  customer_id = "7569"
  support_contract = "silver"
}

You can now add the config dictionary into vars.

vars += config

Now it looks like the following in the first iteration:

customer = "cust 1"
vars = {
  http_uri = "/shop"
  customer_name = "Customer 1"
  customer_id = "7568"
  support_contract = "gold"
}

Remember, you know this structure already. Custom attributes can also be accessed by using the indexer syntax.

  vars.http_uri = ... + config.http_uri

can also be written as

  vars += config
  vars.http_uri = ... + vars.http_uri

Groups

A group is a collection of similar objects. Groups are primarily used as a visualization aid in web interfaces.

Group membership is defined at the respective object itself. If you have a hostgroup name windows for example, and want to assign specific hosts to this group for later viewing the group on your alert dashboard, first create a HostGroup object:

object HostGroup "windows" {
  display_name = "Windows Servers"
}

Then add your hosts to this group:

template Host "windows-server" {
  groups += [ "windows" ]
}

object Host "mssql-srv1" {
  import "windows-server"

  vars.mssql_port = 1433
}

object Host "mssql-srv2" {
  import "windows-server"

  vars.mssql_port = 1433
}

This can be done for service and user groups the same way:

object UserGroup "windows-mssql-admins" {
  display_name = "Windows MSSQL Admins"
}

template User "generic-windows-mssql-users" {
  groups += [ "windows-mssql-admins" ]
}

object User "win-mssql-noc" {
  import "generic-windows-mssql-users"

  email = "noc@example.com"
}

object User "win-mssql-ops" {
  import "generic-windows-mssql-users"

  email = "ops@example.com"
}

Group Membership Assign

Instead of manually assigning each object to a group you can also assign objects to a group based on their attributes:

object HostGroup "prod-mssql" {
  display_name = "Production MSSQL Servers"

  assign where host.vars.mssql_port && host.vars.prod_mysql_db
  ignore where host.vars.test_server == true
  ignore where match("*internal", host.name)
}

In this example all hosts with the vars attribute mssql_port will be added as members to the host group mssql. However, all hosts matching the string \*internal or with the test_server attribute set to true are not added to this group.

Details on the assign where syntax can be found in the Language Reference.

Notifications

Notifications for service and host problems are an integral part of your monitoring setup.

When a host or service is in a downtime, a problem has been acknowledged or the dependency logic determined that the host/service is unreachable, no notifications are sent. You can configure additional type and state filters refining the notifications being actually sent.

There are many ways of sending notifications, e.g. by email, XMPP, IRC, Twitter, etc. On its own Icinga 2 does not know how to send notifications. Instead it relies on external mechanisms such as shell scripts to notify users. More notification methods are listed in the addons and plugins chapter.

A notification specification requires one or more users (and/or user groups) who will be notified in case of problems. These users must have all custom attributes defined which will be used in the NotificationCommand on execution.

The user icingaadmin in the example below will get notified only on Warning and Critical problems. In addition to that Recovery notifications are sent (they require the OK state).

object User "icingaadmin" {
  display_name = "Icinga 2 Admin"
  enable_notifications = true
  states = [ OK, Warning, Critical ]
  types = [ Problem, Recovery ]
  email = "icinga@localhost"
}

If you don't set the states and types configuration attributes for the User object, notifications for all states and types will be sent.

Details on troubleshooting notification problems can be found here.

Note

Make sure that the notification feature is enabled in order to execute notification commands.

You should choose which information you (and your notified users) are interested in case of emergency, and also which information does not provide any value to you and your environment.

An example notification command is explained here.

You can add all shared attributes to a Notification template which is inherited to the defined notifications. That way you'll save duplicated attributes in each Notification object. Attributes can be overridden locally.

template Notification "generic-notification" {
  interval = 15m

  command = "mail-service-notification"

  states = [ Warning, Critical, Unknown ]
  types = [ Problem, Acknowledgement, Recovery, Custom, FlappingStart,
            FlappingEnd, DowntimeStart, DowntimeEnd, DowntimeRemoved ]

  period = "24x7"
}

The time period 24x7 is included as example configuration with Icinga 2.

Use the apply keyword to create Notification objects for your services:

apply Notification "notify-cust-xy-mysql" to Service {
  import "generic-notification"

  users = [ "noc-xy", "mgmt-xy" ]

  assign where match("*has gold support 24x7*", service.notes) && (host.vars.customer == "customer-xy" || host.vars.always_notify == true
  ignore where match("*internal", host.name) || (service.vars.priority < 2 && host.vars.is_clustered == true)
}

Instead of assigning users to notifications, you can also add the user_groups attribute with a list of user groups to the Notification object. Icinga 2 will send notifications to all group members.

Note

Only users who have been notified of a problem before (Warning, Critical, Unknown states for services, Down for hosts) will receive Recovery notifications.

Icinga 2 v2.10 allows you to configure a User object with Acknowledgement and/or Recovery without a Problem notification. These notifications will be sent without any problem notifications beforehand, and can be used for e.g. ticket systems.

object User "ticketadmin" {
  display_name = "Ticket Admin"
  enable_notifications = true
  states = [ OK, Warning, Critical ]
  types = [ Acknowledgement, Recovery ]
  email = "ticket@localhost"
}

Notifications: Users from Host/Service

A common pattern is to store the users and user groups on the host or service objects instead of the notification object itself.

The sample configuration provided in hosts.conf and notifications.conf already provides an example for this question.

Tip

Please make sure to read the apply and custom variable values chapter to fully understand these examples.

Specify the user and groups as nested custom variable on the host object:

object Host "icinga2-agent1.localdomain" {
  [...]

  vars.notification["mail"] = {
    groups = [ "icingaadmins" ]
    users = [ "icingaadmin" ]
  }
  vars.notification["sms"] = {
    users = [ "icingaadmin" ]
  }
}

As you can see, there is the option to use two different notification apply rules here: One for mail and one for sms.

This example assigns the users and groups nested keys from the notification custom variable to the actual notification object attributes.

Since errors are hard to debug if host objects don't specify the required configuration attributes, you can add a safety condition which logs which host object is affected.

critical/config: Host 'icinga2-client3.localdomain' does not specify required user/user_groups configuration attributes for notification 'mail-icingaadmin'.

You can also use the script debugger for more advanced insights.

apply Notification "mail-host-notification" to Host {
  [...]

  /* Log which host does not specify required user/user_groups attributes. This will fail immediately during config validation and help a lot. */
  if (len(host.vars.notification.mail.users) == 0 && len(host.vars.notification.mail.user_groups) == 0) {
    log(LogCritical, "config", "Host '" + host.name + "' does not specify required user/user_groups configuration attributes for notification '" + name + "'.")
  }

  users = host.vars.notification.mail.users
  user_groups = host.vars.notification.mail.groups

  assign where host.vars.notification.mail && typeof(host.vars.notification.mail) == Dictionary
}

apply Notification "sms-host-notification" to Host {
  [...]

  /* Log which host does not specify required user/user_groups attributes. This will fail immediately during config validation and help a lot. */
  if (len(host.vars.notification.sms.users) == 0 && len(host.vars.notification.sms.user_groups) == 0) {
    log(LogCritical, "config", "Host '" + host.name + "' does not specify required user/user_groups configuration attributes for notification '" + name + "'.")
  }

  users = host.vars.notification.sms.users
  user_groups = host.vars.notification.sms.groups

  assign where host.vars.notification.sms && typeof(host.vars.notification.sms) == Dictionary
}

The example above uses typeof as safety function to ensure that the mail key really provides a dictionary as value. Otherwise the configuration validation could fail if an admin adds something like this on another host:

  vars.notification.mail = "yes"

You can also do a more fine granular assignment on the service object:

apply Service "http" {
  [...]

  vars.notification["mail"] = {
    groups = [ "icingaadmins" ]
    users = [ "icingaadmin" ]
  }

  [...]
}

This notification apply rule is different to the one above. The service notification users and groups are inherited from the service and if not set, from the host object. A default user is set too.

apply Notification "mail-service-notification" to Service {
  [...]

  if (service.vars.notification.mail.users) {
    users = service.vars.notification.mail.users
  } else if (host.vars.notification.mail.users) {
    users = host.vars.notification.mail.users
  } else {
    /* Default user who receives everything. */
    users = [ "icingaadmin" ]
  }

  if (service.vars.notification.mail.groups) {
    user_groups = service.vars.notification.mail.groups
  } else if (host.vars.notification.mail.groups) {
    user_groups = host.vars.notification.mail.groups
  }

  assign where ( host.vars.notification.mail && typeof(host.vars.notification.mail) == Dictionary ) || ( service.vars.notification.mail && typeof(service.vars.notification.mail) == Dictionary )
}

Notification Escalations

When a problem notification is sent and a problem still exists at the time of re-notification you may want to escalate the problem to the next support level. A different approach is to configure the default notification by email, and escalate the problem via SMS if not already solved.

You can define notification start and end times as additional configuration attributes making the Notification object a so-called notification escalation. Using templates you can share the basic notification attributes such as users or the interval (and override them for the escalation then).

Using the example from above, you can define additional users being escalated for SMS notifications between start and end time.

object User "icinga-oncall-2nd-level" {
  display_name = "Icinga 2nd Level"

  vars.mobile = "+1 555 424642"
}

object User "icinga-oncall-1st-level" {
  display_name = "Icinga 1st Level"

  vars.mobile = "+1 555 424642"
}

Define an additional NotificationCommand for SMS notifications.

Note

The example is not complete as there are many different SMS providers. Please note that sending SMS notifications will require an SMS provider or local hardware with an active SIM card.

object NotificationCommand "sms-notification" {
   command = [
     PluginDir + "/send_sms_notification",
     "$mobile$",
     "..."
}

The two new notification escalations are added onto the local host and its service ping4 using the generic-notification template. The user icinga-oncall-2nd-level will get notified by SMS (sms-notification command) after 30m until 1h.

Note

The interval was set to 15m in the generic-notification template example. Lower that value in your escalations by using a secondary template or by overriding the attribute directly in the notifications array position for escalation-sms-2nd-level.

If the problem does not get resolved nor acknowledged preventing further notifications, the escalation-sms-1st-level user will be escalated 1h after the initial problem was notified, but only for one hour (2h as end key for the times dictionary).

apply Notification "mail" to Service {
  import "generic-notification"

  command = "mail-notification"
  users = [ "icingaadmin" ]

  assign where service.name == "ping4"
}

apply Notification "escalation-sms-2nd-level" to Service {
  import "generic-notification"

  command = "sms-notification"
  users = [ "icinga-oncall-2nd-level" ]

  times = {
    begin = 30m
    end = 1h
  }

  assign where service.name == "ping4"
}

apply Notification "escalation-sms-1st-level" to Service {
  import "generic-notification"

  command = "sms-notification"
  users = [ "icinga-oncall-1st-level" ]

  times = {
    begin = 1h
    end = 2h
  }

  assign where service.name == "ping4"
}

Notification Delay

Sometimes the problem in question should not be announced when the notification is due (the object reaching the HARD state), but after a certain period. In Icinga 2 you can use the times dictionary and set begin = 15m as key and value if you want to postpone the notification window for 15 minutes. Leave out the end key -- if not set, Icinga 2 will not check against any end time for this notification.

Note

Setting the end key to 0 will stop sending notifications immediately when a problem occurs, effectively disabling the notification.

Make sure to specify a relatively low notification interval to get notified soon enough again.

apply Notification "mail" to Service {
  import "generic-notification"

  command = "mail-notification"
  users = [ "icingaadmin" ]

  interval = 5m

  times.begin = 15m // delay notification window

  assign where service.name == "ping4"
}

Also note that this mechanism doesn't take downtimes etc. into account, only the HARD state change time matters. E.g. for a problem which occurred in the middle of a downtime from 2 PM to 4 PM times.begin = 2h means 5 PM, not 6 PM.

Disable Re-notifications

If you prefer to be notified only once, you can disable re-notifications by setting the interval attribute to 0.

apply Notification "notify-once" to Service {
  import "generic-notification"

  command = "mail-notification"
  users = [ "icingaadmin" ]

  interval = 0 // disable re-notification

  assign where service.name == "ping4"
}

Notification Filters by State and Type

If there are no notification state and type filter attributes defined at the Notification or User object, Icinga 2 assumes that all states and types are being notified.

Available state and type filters for notifications are:

template Notification "generic-notification" {

  states = [ OK, Warning, Critical, Unknown ]
  types = [ Problem, Acknowledgement, Recovery, Custom, FlappingStart,
            FlappingEnd, DowntimeStart, DowntimeEnd, DowntimeRemoved ]
}

Commands

Icinga 2 uses three different command object types to specify how checks should be performed, notifications should be sent, and events should be handled.

Check Commands

CheckCommand objects define the command line how a check is called.

CheckCommand objects are referenced by Host and Service objects using the check_command attribute.

Note

Make sure that the checker feature is enabled in order to execute checks.

Integrate the Plugin with a CheckCommand Definition

Unless you have done so already, download your check plugin and put it into the PluginDir directory. The following example uses the check_mysql plugin contained in the Monitoring Plugins package.

The plugin path and all command arguments are made a list of double-quoted string arguments for proper shell escaping.

Call the check_disk plugin with the --help parameter to see all available options. Our example defines warning (-w) and critical (-c) thresholds for the disk usage. Without any partition defined (-p) it will check all local partitions.

icinga@icinga2 $ /usr/lib64/nagios/plugins/check_mysql --help
...
This program tests connections to a MySQL server

Usage:
check_mysql [-d database] [-H host] [-P port] [-s socket]
[-u user] [-p password] [-S] [-l] [-a cert] [-k key]
[-C ca-cert] [-D ca-dir] [-L ciphers] [-f optfile] [-g group]

Next step is to understand how command parameters are being passed from a host or service object, and add a CheckCommand definition based on these required parameters and/or default values.

Please continue reading in the plugins section for additional integration examples.

Passing Check Command Parameters from Host or Service

Check command parameters are defined as custom variables which can be accessed as runtime macros by the executed check command.

The check command parameters for ITL provided plugin check command definitions are documented here, for example disk.

In order to practice passing command parameters you should integrate your own plugin.

The following example will use check_mysql provided by the Monitoring Plugins.

Define the default check command custom variables, for example mysql_user and mysql_password (freely definable naming schema) and optional their default threshold values. You can then use these custom variables as runtime macros for command arguments on the command line.

Tip

Use a common command type as prefix for your command arguments to increase readability. mysql_user helps understanding the context better than just user as argument.

The default custom variables can be overridden by the custom variables defined in the host or service using the check command my-mysql. The custom variables can also be inherited from a parent template using additive inheritance (+=).

# vim /etc/icinga2/conf.d/commands.conf

object CheckCommand "my-mysql" {
  command = [ PluginDir + "/check_mysql" ] //constants.conf -> const PluginDir

  arguments = {
    "-H" = "$mysql_host$"
    "-u" = {
      required = true
      value = "$mysql_user$"
    }
    "-p" = "$mysql_password$"
    "-P" = "$mysql_port$"
    "-s" = "$mysql_socket$"
    "-a" = "$mysql_cert$"
    "-d" = "$mysql_database$"
    "-k" = "$mysql_key$"
    "-C" = "$mysql_ca_cert$"
    "-D" = "$mysql_ca_dir$"
    "-L" = "$mysql_ciphers$"
    "-f" = "$mysql_optfile$"
    "-g" = "$mysql_group$"
    "-S" = {
      set_if = "$mysql_check_slave$"
      description = "Check if the slave thread is running properly."
    }
    "-l" = {
      set_if = "$mysql_ssl$"
      description = "Use ssl encryption"
    }
  }

  vars.mysql_check_slave = false
  vars.mysql_ssl = false
  vars.mysql_host = "$address$"
}

The check command definition also sets mysql_host to the $address$ default value. You can override this command parameter if for example your MySQL host is not running on the same server's ip address.

Make sure pass all required command parameters, such as mysql_user, mysql_password and mysql_database. MysqlUsername and MysqlPassword are specified as global constants in this example.

# vim /etc/icinga2/conf.d/services.conf

apply Service "mysql-icinga-db-health" {
  import "generic-service"

  check_command = "my-mysql"

  vars.mysql_user = MysqlUsername
  vars.mysql_password = MysqlPassword

  vars.mysql_database = "icinga"
  vars.mysql_host = "192.168.33.11"

  assign where match("icinga2*", host.name)
  ignore where host.vars.no_health_check == true
}

Take a different example: The example host configuration in hosts.conf also applies an ssh service check. Your host's ssh port is not the default 22, but set to 2022. You can pass the command parameter as custom variable ssh_port directly inside the service apply rule inside services.conf:

apply Service "ssh" {
  import "generic-service"

  check_command = "ssh"
  vars.ssh_port = 2022 //custom command parameter

  assign where (host.address || host.address6) && host.vars.os == "Linux"
}

If you prefer this being configured at the host instead of the service, modify the host configuration object instead. The runtime macro resolving order is described here.

object Host "icinga2-agent1.localdomain {
...
  vars.ssh_port = 2022
}

Passing Check Command Parameters Using Apply For

The host localhost with the generated services from the basic-partitions dictionary (see apply for for details) checks a basic set of disk partitions with modified custom variables (warning thresholds at 10%, critical thresholds at 5% free disk space).

The custom variable disk_partition can either hold a single string or an array of string values for passing multiple partitions to the check_disk check plugin.

object Host "my-server" {
  import "generic-host"
  address = "127.0.0.1"
  address6 = "::1"

  vars.local_disks["basic-partitions"] = {
    disk_partitions = [ "/", "/tmp", "/var", "/home" ]
  }
}

apply Service for (disk => config in host.vars.local_disks) {
  import "generic-service"
  check_command = "my-disk"

  vars += config

  vars.disk_wfree = "10%"
  vars.disk_cfree = "5%"
}

More details on using arrays in custom variables can be found in this chapter.

Command Arguments

Next to the short command array specified in the command object, it is advised to define plugin/script parameters in the arguments dictionary attribute.

The value of the --parameter key itself is a dictionary with additional keys. They allow to create generic command objects and are also for documentation purposes, e.g. with the description field copying the plugin's help text in there. The Icinga Director uses this field to show the argument's purpose when selecting it.

  arguments = {
    "--parameter" = {
      description = "..."
      value = "..."
    }
  }

Each argument is optional by default and is omitted if the value is not set.

Learn more about integrating plugins with CheckCommand objects in this chapter.

There are additional possibilities for creating a command only once, with different parameters and arguments, shown below.

Command Arguments: Value

In order to find out about the command argument, call the plugin's help or consult the README.

./check_systemd.py --help

...

  -u UNIT, --unit UNIT  Name of the systemd unit that is beeing tested.

Whenever the long parameter name is available, prefer this over the short one.

  arguments = {
    "--unit" = {

    }
  }

Define a unique prefix for the command's specific arguments. Best practice is to follow this schema:

<command name>_<parameter name>

Therefore use systemd_ as prefix, and use the long plugin parameter name unit inside the runtime macro syntax.

  arguments = {
    "--unit" = {
      value = "$systemd_unit$"
    }
  }

In order to specify a default value, specify a custom variable inside the CheckCommand object.

  vars.systemd_unit = "icinga2"

This value can be overridden from the host/service object as command parameters.

Command Arguments: Description

Best practice, also inside the ITL, is to always copy the command parameter help output into the description field of your check command.

Learn more about integrating plugins with CheckCommand objects in this chapter.

With the example above, inspect the parameter's help text.

./check_systemd.py --help

...

  -u UNIT, --unit UNIT  Name of the systemd unit that is beeing tested.

Copy this into the command arguments description entry.

  arguments = {
    "--unit" = {
      value = "$systemd_unit$"
      description = "Name of the systemd unit that is beeing tested."
    }
  }

Command Arguments: Required

Specifies whether this command argument is required, or not. By default all arguments are optional.

Tip

Good plugins provide optional parameters in square brackets, e.g. [-w SECONDS].

The required field can be toggled with a boolean value.

  arguments = {
    "--host" = {
      value = "..."
      description = "..."
      required = true
    }
  }

Whenever the check is executed and the argument is missing, Icinga logs an error. This allows to better debug configuration errors instead of sometimes unreadable plugin errors when parameters are missing.

Command Arguments: Skip Key

The arguments attribute requires a key, empty values are not allowed. To overcome this for parameters which don't need the name in front of the value, use the skip_key boolean toggle.

  command = [ PrefixDir + "/bin/icingacli", "businessprocess", "process", "check" ]

  arguments = {
    "--process" = {
      value = "$icingacli_businessprocess_process$"
      description = "Business process to monitor"
      skip_key = true
      required = true
      order = -1
    }
  }

The service specifies the custom variable icingacli_businessprocess_process.

  vars.icingacli_businessprocess_process = "bp-shop-web"

This results in this command line without the --process parameter:

'/bin/icingacli' 'businessprocess' 'process' 'check' 'bp-shop-web'

You can use this method to put everything into the arguments attribute in a defined order and without keys. This avoids entries in the command attributes too.

Command Arguments: Set If

This can be used for the following scenarios:

Parameters without value, e.g. --sni.

  command = [ PluginDir + "/check_http"]

  arguments = {
    "--sni" = {
      set_if = "$http_sni$"
    }
  }

Whenever a host/service object sets the http_sni custom variable to true, the parameter is added to the command line.

'/usr/lib64/nagios/plugins/check_http' '--sni'

Numeric values are allowed too.

Parameters with value, but additionally controlled with an extra custom variable boolean flag.

The following example is taken from the postgres CheckCommand. The host parameter should use a value but only whenever the postgres_unixsocket custom variable is set to false.

Note: set_if is using a runtime lambda function because the value is evaluated at runtime. This is explained in this chapter.

  command = [ PluginContribDir + "/check_postgres.pl" ]

  arguments = {
    "-H" = {
      value = "$postgres_host$"
      set_if = {{ macro("$postgres_unixsocket$") == false }}
      description = "hostname(s) to connect to; defaults to none (Unix socket)"
  }

An executed check for this host and services ...

object Host "postgresql-cluster" {
  // ...

  vars.postgres_host = "192.168.56.200"
  vars.postgres_unixsocket = false
}

... use the following command line:

'/usr/lib64/nagios/plugins/check_postgres.pl' '-H' '192.168.56.200'

Host/service objects which set postgres_unixsocket to false don't add the -H parameter and its value to the command line.

References: abbreviated lambda syntax, macro.

Command Arguments: Order

Plugin may require parameters in a special order. One after the other, or e.g. one parameter always in the first position.

  arguments = {
    "--first" = {
      value = "..."
      description = "..."
      order = -5
    }
    "--second" = {
      value = "..."
      description = "..."
      order = -4
    }
    "--last" = {
      value = "..."
      description = "..."
      order = 99
    }
  }

Keep in mind that positional arguments need to be tested thoroughly.

Command Arguments: Repeat Key

Parameters can use Array as value type. Whenever Icinga encounters an array, it repeats the parameter key and each value element by default.

  command = [ NscpPath + "\\nscp.exe", "client" ]

  arguments = {
    "-a" = {
      value = "$nscp_arguments$"
      description = "..."
      repeat_key = true
    }
  }

On a host/service object, specify the nscp_arguments custom variable as an array.

  vars.nscp_arguments = [ "exclude=sppsvc", "exclude=ShellHWDetection" ]

This translates into the following command line:

nscp.exe 'client' '-a' 'exclude=sppsvc' '-a' 'exclude=ShellHWDetection'

If the plugin requires you to pass the list without repeating the key, set repeat_key = false in the argument definition.

  command = [ NscpPath + "\\nscp.exe", "client" ]

  arguments = {
    "-a" = {
      value = "$nscp_arguments$"
      description = "..."
      repeat_key = false
    }
  }

This translates into the following command line:

nscp.exe 'client' '-a' 'exclude=sppsvc' 'exclude=ShellHWDetection'

Command Arguments: Key

The arguments attribute requires unique keys. Sometimes, you'll need to override this in the resulting command line with same key names. Therefore you can specifically override the arguments key.

arguments = {
  "--key1" = {
    value = "..."
    key = "-specialkey"
  }
  "--key2" = {
    value = "..."
    key = "-specialkey"
  }
}

This results in the following command line:

  '-specialkey' '...' '-specialkey' '...'

Environment Variables

The env command object attribute specifies a list of environment variables with values calculated from custom variables which should be exported as environment variables prior to executing the command.

This is useful for example for hiding sensitive information on the command line output when passing credentials to database checks:

object CheckCommand "mysql" {
  command = [ PluginDir + "/check_mysql" ]

  arguments = {
    "-H" = "$mysql_address$"
    "-d" = "$mysql_database$"
  }

  vars.mysql_address = "$address$"
  vars.mysql_database = "icinga"
  vars.mysql_user = "icinga_check"
  vars.mysql_pass = "password"

  env.MYSQLUSER = "$mysql_user$"
  env.MYSQLPASS = "$mysql_pass$"
}

The executed command line visible with ps or top looks like this and hides the database credentials in the user's environment.

/usr/lib/nagios/plugins/check_mysql -H 192.168.56.101 -d icinga

Note

If the CheckCommand also supports setting the parameter in the command line, ensure to use a different name for the custom variable. Otherwise Icinga 2 adds the command line parameter.

If a specific CheckCommand object provided with the Icinga Template Library needs additional environment variables, you can import it into a new custom CheckCommand object and add additional env keys. Example for the mysql_health CheckCommand:

object CheckCommand "mysql_health_env" {
  import "mysql_health"

  // https://labs.consol.de/nagios/check_mysql_health/
  env.NAGIOS__SERVICEMYSQL_USER = "$mysql_health_env_username$"
  env.NAGIOS__SERVICEMYSQL_PASS = "$mysql_health_env_password$"
}

Specify the custom variables mysql_health_env_username and mysql_health_env_password in the service object then.

Note

Keep in mind that the values are still visible with the debug console and the inspect mode in the Icinga Director.

You can also set global environment variables in the application's sysconfig configuration file, e.g. HOME or specific library paths for Oracle. Beware that these environment variables can be used by any CheckCommand object and executed plugin and can leak sensitive information.

Notification Commands

NotificationCommand objects define how notifications are delivered to external interfaces (email, XMPP, IRC, Twitter, etc.). NotificationCommand objects are referenced by Notification objects using the command attribute.

Note

Make sure that the notification feature is enabled in order to execute notification commands.

While it's possible to specify an entire notification command right in the NotificationCommand object it is generally advisable to create a shell script in the /etc/icinga2/scripts directory and have the NotificationCommand object refer to that.

A fresh Icinga 2 install comes with with two example scripts for host and service notifications by email. Based on the Icinga 2 runtime macros (such as $service.output$ for the current check output) it's possible to send email to the user(s) associated with the notification itself ($user.email$). Feel free to take these scripts as a starting point for your own individual notification solution - and keep in mind that nearly everything is technically possible.

Information needed to generate notifications is passed to the scripts as arguments. The NotificationCommand objects mail-host-notification and mail-service-notification correspond to the shell scripts mail-host-notification.sh and mail-service-notification.sh in /etc/icinga2/scripts and define default values for arguments. These defaults can always be overwritten locally.

Note

This example requires the mail binary installed on the Icinga 2 master.

Depending on the distribution, you need a local mail transfer agent (MTA) such as Postfix, Exim or Sendmail in order to send emails.

These tools virtually provide the mail binary executed by the notification scripts below.

mail-host-notification

The mail-host-notification NotificationCommand object uses the example notification script located in /etc/icinga2/scripts/mail-host-notification.sh.

Here is a quick overview of the arguments that can be used. See also host runtime macros for further information.

Name	Description
notification_date	Required. Date and time. Defaults to $icinga.long_date_time$.
notification_hostname	Required. The host's FQDN. Defaults to $host.name$.
notification_hostdisplayname	Required. The host's display name. Defaults to $host.display_name$.
notification_hostoutput	Required. Output from host check. Defaults to $host.output$.
notification_useremail	Required. The notification's recipient(s). Defaults to $user.email$.
notification_hoststate	Required. Current state of host. Defaults to $host.state$.
notification_type	Required. Type of notification. Defaults to $notification.type$.
notification_address	Optional. The host's IPv4 address. Defaults to $address$.
notification_address6	Optional. The host's IPv6 address. Defaults to $address6$.
notification_author	Optional. Comment author. Defaults to $notification.author$.
notification_comment	Optional. Comment text. Defaults to $notification.comment$.
notification_from	Optional. Define a valid From: string (e.g. "Icinga 2 Host Monitoring <icinga@example.com>"). Requires GNU mailutils (Debian/Ubuntu) or mailx (RHEL/SUSE).
notification_icingaweb2url	Optional. Define URL to your Icinga Web 2 (e.g. "https://www.example.com/icingaweb2")
notification_logtosyslog	Optional. Set true to log notification events to syslog; useful for debugging. Defaults to false.

mail-service-notification

The mail-service-notification NotificationCommand object uses the example notification script located in /etc/icinga2/scripts/mail-service-notification.sh.

Here is a quick overview of the arguments that can be used. See also service runtime macros for further information.

Name	Description
notification_date	Required. Date and time. Defaults to $icinga.long_date_time$.
notification_hostname	Required. The host's FQDN. Defaults to $host.name$.
notification_servicename	Required. The service name. Defaults to $service.name$.
notification_hostdisplayname	Required. Host display name. Defaults to $host.display_name$.
notification_servicedisplayname	Required. Service display name. Defaults to $service.display_name$.
notification_serviceoutput	Required. Output from service check. Defaults to $service.output$.
notification_useremail	Required. The notification's recipient(s). Defaults to $user.email$.
notification_servicestate	Required. Current state of host. Defaults to $service.state$.
notification_type	Required. Type of notification. Defaults to $notification.type$.
notification_address	Optional. The host's IPv4 address. Defaults to $address$.
notification_address6	Optional. The host's IPv6 address. Defaults to $address6$.
notification_author	Optional. Comment author. Defaults to $notification.author$.
notification_comment	Optional. Comment text. Defaults to $notification.comment$.
notification_from	Optional. Define a valid From: string (e.g. "Icinga 2 Host Monitoring <icinga@example.com>"). Requires GNU mailutils (Debian/Ubuntu) or mailx (RHEL/SUSE).
notification_icingaweb2url	Optional. Define URL to your Icinga Web 2 (e.g. "https://www.example.com/icingaweb2")
notification_logtosyslog	Optional. Set true to log notification events to syslog; useful for debugging. Defaults to false.

Event Commands

Unlike notifications, event commands for hosts/services are called on every check execution if one of these conditions matches:

• The host/service is in a soft state
• The host/service state changes into a hard state
• The host/service state recovers from a soft or hard state to OK/Up

EventCommand objects are referenced by Host and Service objects with the event_command attribute.

Therefore the EventCommand object should define a command line evaluating the current service state and other service runtime attributes available through runtime variables. Runtime macros such as $service.state_type$ and $service.state$ will be processed by Icinga 2 and help with fine-granular triggered events

If the host/service is located on a client as command endpoint the event command will be executed on the client itself (similar to the check command).

Common use case scenarios are a failing HTTP check which requires an immediate restart via event command. Another example would be an application that is not responding and therefore requires a restart. You can also use event handlers to forward more details on state changes and events than the typical notification alerts provide.

Use Event Commands to Send Information from the Master

This example sends a web request from the master node to an external tool for every event triggered on a businessprocess service.

Define an EventCommand object send_to_businesstool which sends state changes to the external tool.

object EventCommand "send_to_businesstool" {
  command = [
    "/usr/bin/curl",
    "-s",
    "-X PUT"
  ]

  arguments = {
    "-H" = {
      value ="$businesstool_url$"
      skip_key = true
    }
    "-d" = "$businesstool_message$"
  }

  vars.businesstool_url = "http://localhost:8080/businesstool"
  vars.businesstool_message = "$host.name$ $service.name$ $service.state$ $service.state_type$ $service.check_attempt$"
}

Set the event_command attribute to send_to_businesstool on the Service.

object Service "businessprocess" {
  host_name = "businessprocess"

  check_command = "icingacli-businessprocess"
  vars.icingacli_businessprocess_process = "icinga"
  vars.icingacli_businessprocess_config = "training"

  event_command = "send_to_businesstool"
}

In order to test this scenario you can run:

nc -l 8080

This allows to catch the web request. You can also enable the debug log and search for the event command execution log message.

tail -f /var/log/icinga2/debug.log | grep EventCommand

Feed in a check result via REST API action process-check-result or via Icinga Web 2.

Expected Result:

# nc -l 8080
PUT /businesstool HTTP/1.1
User-Agent: curl/7.29.0
Host: localhost:8080
Accept: */*
Content-Length: 47
Content-Type: application/x-www-form-urlencoded

businessprocess businessprocess CRITICAL SOFT 1

Use Event Commands to Restart Service Daemon via Command Endpoint on Linux

This example triggers a restart of the httpd service on the local system when the procs service check executed via Command Endpoint fails. It only triggers if the service state is Critical and attempts to restart the service before a notification is sent.

Requirements:

• Icinga 2 as client on the remote node
• icinga user with sudo permissions to the httpd daemon

Example on CentOS 7:

# visudo
icinga  ALL=(ALL) NOPASSWD: /usr/bin/systemctl restart httpd

Note: Distributions might use a different name. On Debian/Ubuntu the service is called apache2.

Define an EventCommand object restart_service which allows to trigger local service restarts. Put it into a global zone to sync its configuration to all clients.

[root@icinga2-master1.localdomain /]# vim /etc/icinga2/zones.d/global-templates/eventcommands.conf

object EventCommand "restart_service" {
  command = [ PluginDir + "/restart_service" ]

  arguments = {
    "-s" = "$service.state$"
    "-t" = "$service.state_type$"
    "-a" = "$service.check_attempt$"
    "-S" = "$restart_service$"
  }

  vars.restart_service = "$procs_command$"
}

This event command triggers the following script which restarts the service. The script only is executed if the service state is CRITICAL. Warning and Unknown states are ignored as they indicate not an immediate failure.

[root@icinga2-agent1.localdomain /]# vim /usr/lib64/nagios/plugins/restart_service

#!/bin/bash

while getopts "s:t:a:S:" opt; do
  case $opt in
    s)
      servicestate=$OPTARG
      ;;
    t)
      servicestatetype=$OPTARG
      ;;
    a)
      serviceattempt=$OPTARG
      ;;
    S)
      service=$OPTARG
      ;;
  esac
done

if ( [ -z $servicestate ] || [ -z $servicestatetype ] || [ -z $serviceattempt ] || [ -z $service ] ); then
  echo "USAGE: $0 -s servicestate -z servicestatetype -a serviceattempt -S service"
  exit 3;
else
  # Only restart on the third attempt of a critical event
  if ( [ $servicestate == "CRITICAL" ] && [ $servicestatetype == "SOFT" ] && [ $serviceattempt -eq 3 ] ); then
    sudo /usr/bin/systemctl restart $service
  fi
fi

[root@icinga2-agent1.localdomain /]# chmod +x /usr/lib64/nagios/plugins/restart_service

Add a service on the master node which is executed via command endpoint on the client. Set the event_command attribute to restart_service, the name of the previously defined EventCommand object.

[root@icinga2-master1.localdomain /]# vim /etc/icinga2/zones.d/master/icinga2-agent1.localdomain.conf

object Service "Process httpd" {
  check_command = "procs"
  event_command = "restart_service"
  max_check_attempts = 4

  host_name = "icinga2-agent1.localdomain"
  command_endpoint = "icinga2-agent1.localdomain"

  vars.procs_command = "httpd"
  vars.procs_warning = "1:10"
  vars.procs_critical = "1:"
}

In order to test this configuration just stop the httpd on the remote host icinga2-agent1.localdomain.

[root@icinga2-agent1.localdomain /]# systemctl stop httpd

You can enable the debug log and search for the executed command line.

[root@icinga2-agent1.localdomain /]# tail -f /var/log/icinga2/debug.log | grep restart_service

Use Event Commands to Restart Service Daemon via Command Endpoint on Windows

This example triggers a restart of the httpd service on the remote system when the service-windows service check executed via Command Endpoint fails. It only triggers if the service state is Critical and attempts to restart the service before a notification is sent.

Requirements:

• Icinga 2 as client on the remote node
• Icinga 2 service with permissions to execute Powershell scripts (which is the default)

Define an EventCommand object restart_service-windows which allows to trigger local service restarts. Put it into a global zone to sync its configuration to all clients.

[root@icinga2-master1.localdomain /]# vim /etc/icinga2/zones.d/global-templates/eventcommands.conf

object EventCommand "restart_service-windows" {
  command = [
    "C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe",
    PluginDir + "/restart_service.ps1"
  ]

  arguments = {
    "-ServiceState" = "$service.state$"
    "-ServiceStateType" = "$service.state_type$"
    "-ServiceAttempt" = "$service.check_attempt$"
    "-Service" = "$restart_service$"
    "; exit" = {
        order = 99
        value = "$$LASTEXITCODE"
    }
  }

  vars.restart_service = "$service_win_service$"
}

This event command triggers the following script which restarts the service. The script only is executed if the service state is CRITICAL. Warning and Unknown states are ignored as they indicate not an immediate failure.

Add the restart_service.ps1 Powershell script into C:\Program Files\Icinga2\sbin:

param(
        [string]$Service                  = '',
        [string]$ServiceState             = '',
        [string]$ServiceStateType         = '',
        [int]$ServiceAttempt              = ''
    )

if (!$Service -Or !$ServiceState -Or !$ServiceStateType -Or !$ServiceAttempt) {
    $scriptName = GCI $MyInvocation.PSCommandPath | Select -Expand Name;
    Write-Host "USAGE: $scriptName -ServiceState servicestate -ServiceStateType servicestatetype -ServiceAttempt serviceattempt -Service service" -ForegroundColor red;
    exit 3;
}

# Only restart on the third attempt of a critical event
if ($ServiceState -eq "CRITICAL" -And $ServiceStateType -eq "SOFT" -And $ServiceAttempt -eq 3) {
    Restart-Service $Service;
}

exit 0;

Add a service on the master node which is executed via command endpoint on the client. Set the event_command attribute to restart_service-windows, the name of the previously defined EventCommand object.

[root@icinga2-master1.localdomain /]# vim /etc/icinga2/zones.d/master/icinga2-agent2.localdomain.conf

object Service "Service httpd" {
  check_command = "service-windows"
  event_command = "restart_service-windows"
  max_check_attempts = 4

  host_name = "icinga2-agent2.localdomain"
  command_endpoint = "icinga2-agent2.localdomain"

  vars.service_win_service = "httpd"
}

In order to test this configuration just stop the httpd on the remote host icinga2-agent1.localdomain.

C:> net stop httpd

You can enable the debug log and search for the executed command line in C:\ProgramData\icinga2\var\log\icinga2\debug.log.

Use Event Commands to Restart Service Daemon via SSH

This example triggers a restart of the httpd daemon via SSH when the http service check fails.

Requirements:

• SSH connection allowed (firewall, packet filters)
• icinga user with public key authentication
• icinga user with sudo permissions to restart the httpd daemon.

Example on Debian:

# ls /home/icinga/.ssh/
authorized_keys

# visudo
icinga  ALL=(ALL) NOPASSWD: /etc/init.d/apache2 restart

Define a generic EventCommand object event_by_ssh which can be used for all event commands triggered using SSH:

[root@icinga2-master1.localdomain /]# vim /etc/icinga2/zones.d/master/local_eventcommands.conf

/* pass event commands through ssh */
object EventCommand "event_by_ssh" {
  command = [ PluginDir + "/check_by_ssh" ]

  arguments = {
    "-H" = "$event_by_ssh_address$"
    "-p" = "$event_by_ssh_port$"
    "-C" = "$event_by_ssh_command$"
    "-l" = "$event_by_ssh_logname$"
    "-i" = "$event_by_ssh_identity$"
    "-q" = {
      set_if = "$event_by_ssh_quiet$"
    }
    "-w" = "$event_by_ssh_warn$"
    "-c" = "$event_by_ssh_crit$"
    "-t" = "$event_by_ssh_timeout$"
  }

  vars.event_by_ssh_address = "$address$"
  vars.event_by_ssh_quiet = false
}

The actual event command only passes the event_by_ssh_command attribute. The event_by_ssh_service custom variable takes care of passing the correct daemon name, while test $service.state_id$ -gt 0 makes sure that the daemon is only restarted when the service is not in an OK state.

object EventCommand "event_by_ssh_restart_service" {
  import "event_by_ssh"

  //only restart the daemon if state > 0 (not-ok)
  //requires sudo permissions for the icinga user
  vars.event_by_ssh_command = "test $service.state_id$ -gt 0 && sudo systemctl restart $event_by_ssh_service$"
}

Now set the event_command attribute to event_by_ssh_restart_service and tell it which service should be restarted using the event_by_ssh_service attribute.

apply Service "http" {
  import "generic-service"
  check_command = "http"

  event_command = "event_by_ssh_restart_service"
  vars.event_by_ssh_service = "$host.vars.httpd_name$"

  //vars.event_by_ssh_logname = "icinga"
  //vars.event_by_ssh_identity = "/home/icinga/.ssh/id_rsa.pub"

  assign where host.vars.httpd_name
}

Specify the httpd_name custom variable on the host to assign the service and set the event handler service.

object Host "remote-http-host" {
  import "generic-host"
  address = "192.168.1.100"

  vars.httpd_name = "apache2"
}

In order to test this configuration just stop the httpd on the remote host icinga2-agent1.localdomain.

[root@icinga2-agent1.localdomain /]# systemctl stop httpd

You can enable the debug log and search for the executed command line.

[root@icinga2-agent1.localdomain /]# tail -f /var/log/icinga2/debug.log | grep by_ssh

Dependencies

Icinga 2 uses host and service Dependency objects for determining their network reachability.

A service can depend on a host, and vice versa. A service has an implicit dependency (parent) to its host. A host to host dependency acts implicitly as host parent relation. When dependencies are calculated, not only the immediate parent is taken into account but all parents are inherited.

The parent_host_name and parent_service_name attributes are mandatory for service dependencies, parent_host_name is required for host dependencies. Apply rules will allow you to determine these attributes in a more dynamic fashion if required.

parent_host_name = "core-router"
parent_service_name = "uplink-port"

Notifications are suppressed by default if a host or service becomes unreachable. You can control that option by defining the disable_notifications attribute.

disable_notifications = false

If the dependency should be triggered in the parent object's soft state, you need to set ignore_soft_states to false.

The dependency state filter must be defined based on the parent object being either a host (Up, Down) or a service (OK, Warning, Critical, Unknown).

The following example will make the dependency fail and trigger it if the parent object is not in one of these states:

states = [ OK, Critical, Unknown ]

In other words

If the parent service object changes into the Warning state, this dependency will fail and render all child objects (hosts or services) unreachable.

You can determine the child's reachability by querying the last_reachable attribute via the REST API.

Note

Reachability calculation depends on fresh and processed check results. If dependencies disable checks for child objects, this won't work reliably.

Implicit Dependencies for Services on Host

Icinga 2 automatically adds an implicit dependency for services on their host. That way service notifications are suppressed when a host is DOWN or UNREACHABLE. This dependency does not overwrite other dependencies and implicitly sets disable_notifications = true and states = [ Up ] for all service objects.

Service checks are still executed. If you want to prevent them from happening, you can apply the following dependency to all services setting their host as parent_host_name and disabling the checks. assign where true matches on all Service objects.

apply Dependency "disable-host-service-checks" to Service {
  disable_checks = true
  assign where true
}

Dependencies for Network Reachability

A common scenario is the Icinga 2 server behind a router. Checking internet access by pinging the Google DNS server google-dns is a common method, but will fail in case the dsl-router host is down. Therefore the example below defines a host dependency which acts implicitly as parent relation too.

Furthermore the host may be reachable but ping probes are dropped by the router's firewall. In case the dsl-router's ping4 service check fails, all further checks for the ping4 service on host google-dns service should be suppressed. This is achieved by setting the disable_checks attribute to true.

object Host "dsl-router" {
  import "generic-host"
  address = "192.168.1.1"
}

object Host "google-dns" {
  import "generic-host"
  address = "8.8.8.8"
}

apply Service "ping4" {
  import "generic-service"

  check_command = "ping4"

  assign where host.address
}

apply Dependency "internet" to Host {
  parent_host_name = "dsl-router"
  disable_checks = true
  disable_notifications = true

  assign where host.name != "dsl-router"
}

apply Dependency "internet" to Service {
  parent_host_name = "dsl-router"
  parent_service_name = "ping4"
  disable_checks = true

  assign where host.name != "dsl-router"
}

Redundancy Groups

Sometimes you want dependencies to accumulate, i.e. to consider the parent reachable only if no dependency is violated. Sometimes you want them to be regarded as redundant, i.e. to consider the parent unreachable only if no dependency is fulfilled. Think of a host connected to both a network and a storage switch vs. a host connected to redundant routers.

Sometimes you even want a mixture of both. Think of a service like SSH depeding on both LDAP and DNS to function, while operating redundant LDAP servers as well as redundant DNS resolvers.

Before v2.12, Icinga regarded all dependecies as cumulative. In v2.12 and v2.13, Icinga regarded all dependencies redundant. The latter led to unrelated services being inadvertantly regarded to be redundant to each other.

v2.14 restored the former behavior and allowed to override it. I.e. all dependecies are regarded as essential for the parent by default. Specifying the redundancy_group attribute for two dependecies of a child object with the equal value causes them to be regarded as redundant (only inside that redundancy group).

Apply Dependencies based on Custom Variables

You can use apply rules to set parent or child attributes, e.g. parent_host_name to other objects' attributes.

A common example are virtual machines hosted on a master. The object name of that master is auto-generated from your CMDB or VMWare inventory into the host's custom variables (or a generic template for your cloud).

Define your master host object:

/* your master */
object Host "master.example.com" {
  import "generic-host"
}

Add a generic template defining all common host attributes:

/* generic template for your virtual machines */
template Host "generic-vm" {
  import "generic-host"
}

Add a template for all hosts on your example.com cloud setting custom variable vm_parent to master.example.com:

template Host "generic-vm-example.com" {
  import "generic-vm"
  vars.vm_parent = "master.example.com"
}

Define your guest hosts:

object Host "www.example1.com" {
  import "generic-vm-master.example.com"
}

object Host "www.example2.com" {
  import "generic-vm-master.example.com"
}

Apply the host dependency to all child hosts importing the generic-vm template and set the parent_host_name to the previously defined custom variable host.vars.vm_parent.

apply Dependency "vm-host-to-parent-master" to Host {
  parent_host_name = host.vars.vm_parent
  assign where "generic-vm" in host.templates
}

You can extend this example, and make your services depend on the master.example.com host too. Their local scope allows you to use host.vars.vm_parent similar to the example above.

apply Dependency "vm-service-to-parent-master" to Service {
  parent_host_name = host.vars.vm_parent
  assign where "generic-vm" in host.templates
}

That way you don't need to wait for your guest hosts becoming unreachable when the master host goes down. Instead the services will detect their reachability immediately when executing checks.

Note

This method with setting locally scoped variables only works in apply rules, but not in object definitions.

Dependencies for Agent Checks

Another good example are agent based checks. You would define a health check for the agent daemon responding to your requests, and make all other services querying that daemon depend on that health check.

apply Service "agent-health" {
  check_command = "cluster-zone"

  display_name = "cluster-health-" + host.name

  /* This follows the convention that the agent zone name is the FQDN which is the same as the host object name. */
  vars.cluster_zone = host.name

  assign where host.vars.agent_endpoint
}

Now, make all other agent based checks dependent on the OK state of the agent-health service.

apply Dependency "agent-health-check" to Service {
  parent_service_name = "agent-health"

  states = [ OK ] // Fail if the parent service state switches to NOT-OK
  disable_notifications = true

  assign where host.vars.agent_endpoint // Automatically assigns all agent endpoint checks as child services on the matched host
  ignore where service.name == "agent-health" // Avoid a self reference from child to parent
}

This is described in detail in this chapter.