icinga2/doc/3-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 in mind. If you are using Windows, you will need to change the services accordingly. See the ITL reference for further information.

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 of the following states:

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

Service States

Services can be in any 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 service is in a critical state.
UNKNOWN	The check could not determine the service's state.

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.
SOFT	The host/service has recently changed state and is being re-checked.

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.

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.

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

Custom Attributes

In addition to built-in attributes you can define your own attributes:

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

Valid values for custom attributes include:

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

Functions as Custom Attributes

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

object CheckCommand "random-value" {
  import "plugin-check-command"

  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 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(" ")
  }}
  ...
}

Acessing 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 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" {
  import "plugin-check-command"

  command = [ PluginDir + "/check_ping", "-H", "$ping_address$" ]

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

  vars.ping_address = "$address$"

  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 attributes, 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 attributes in the Vars constant

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

Here's how you can override the custom attribute 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 attribute 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 attribute for the service. This returns an empty value if the service does not have such a custom attribute no matter whether another object such as the host has this attribute.

Host Runtime Macros

The following host custom attributes 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.

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.

Command Runtime Macros

The following custom attributes are available in all commands:

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

User Runtime Macros

The following custom attributes 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.

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.

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.

Apply Rules

Instead of assigning each object (Service, Notification, Dependency, ScheduledDowntime) based on attribute identifiers for example host_name objects can be applied.

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

• Define the best match.
  • A set of unique custom attributes for these hosts/services?
  • Or group memberships, e.g. a host being a member of a hostgroup, applying services to it?
  • 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.)

Note

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

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

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

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

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.

Match all *mysql* patterns in the host name and (&&) custom attribute prod_mysql_db matches the db-* pattern. All hosts with the custom attribute 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 contains the has gold support 24x7 string AND one of the two condition passes, either the customer host custom attribute is set to customer-xy OR the host custom attribute always_notify is set to true.

The notification is ignored for services whose host name ends with *internal OR the priority custom attribute 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 attribute 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 attribute 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 attributes. 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 attribute
  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 attribute `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, which contains all relevant notification settings, is applied on all host objects where the host.address is defined. Each host object is then checked for custom attributes (host.vars.notification_interval, host.vars.notification_period and host.vars.notification_type). Depending if the custom attibute is set or which value it has, the value from the notification template is dynamically overwritten.

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 = "::1"

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

Now we want to create service checks for if01 and temp, but not bgp. Furthermore we want to pass the snmp oid stored as dictionary value to the custom attribute called vars.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.

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 attribute oids set. It then iterates over all list items inside the for loop and evaluates the assign/ignore where expressions. You can access the loop variable in these expressions, e.g. for ignoring certain values. In this example we'd ignore the bgp identifier and avoid generating an unwanted service. We could extend the configuration by also matching the oid value on certain regex/wildcard patterns for example.

Note

You don't need an assign where expression only checking for existance of the custom attribute.

That way you'll save duplicated apply rules by combining them into one generic apply for rule generating the object name with or without a prefix.

Apply For and Custom Attribute 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 check 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"

By defining the interfaces dictionary with three example interfaces on the cisco-catalyst-6509-34 host object, you'll make sure to pass the custom attribute storage required by the for loop in the service apply rule.

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 attributes 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 = "renote"
     qos = "enabled"
  }
  vars.interfaces["MgmtInterface1"] = {
     iftraffic_community = IftrafficSnmpCommunity
     vlan = "mgmt"
     interface_address = "127.99.0.100" #special management ip
  }
}

You can also omit the "if-" string, then all generated service names are directly taken from the if_name variable value.

The config dictionary contains all key-value pairs for the specific interface in one loop cycle, like iftraffic_units, vlan, and qos for the specified interface.

You can either map the custom attributes from the interface_config dictionary to local custom attributes stashed into vars. If the names match the required command argument parameters already (for example iftraffic_units), you could also add the interface_config dictionary to the vars dictionary using the += operator.

After vars is fully populated, all object attributes can be set calculated from provided host attributes. For strings, you can use string concatention with the + operator.

You can also specifiy the display_name, check command, interval, notes, notes_url, action_url, etc. attributes that way. Attribute strings can be concatenated, for example for adding a more detailed service display_name.

This example also uses if conditions if specific values are not set, adding a local default value. The other way around you can override specific custom attributes inherited from a service template if set.

/* 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 "generic-service"
  check_command = "iftraffic"
  display_name = "IF-" + interface_name

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

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

  /* 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

  /* 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"
  }

  /* 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
  }

  /* 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 = "http://foreman.company.com/hosts/" + host.name
  action_url = "http://snmp.checker.company.com/" + host.name + "/if-" + interface_name
}

This example makes use of the check_iftraffic plugin. The CheckCommand definition can be found in the contributed plugin check commands -- make sure to include them in your icinga2 configuration file.

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 attributes:

# 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 = "renote"

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["xyz"] = {
    http_uri = "/shop"
    customer_name = "Customer xyz"
    customer_id = "7568"
    support_contract = "gold"
  }
  vars.hosting["abc"] = {
    http_uri = "/shop"
    customer_name = "Customer xyz"
    customer_id = "7568"
    support_contract = "silver"
  }
}

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

  vars.qos = "disabled"

  vars += config

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

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 \*internal hosts 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 states and problem and recovery notification types.

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.

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. 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"
}

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

If you are familiar with Icinga 1.x notification_options, please note that they have been split into type and state to allow more fine granular filtering for example on downtimes and flapping. You can filter for acknowledgements and custom notifications too.

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

CheckCommand objects require the ITL template plugin-check-command to support native plugin based check methods.

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 attributes 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 installation.

Define the default check command custom attributes, for example mysql_user and mysql_password (freely definable naming schema) and optional their default threshold values. You can then use these custom attributes 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 attributes can be overridden by the custom attributes defined in the host or service using the check command my-mysql. The custom attributes can also be inherited from a parent template using additive inheritance (+=).

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

object CheckCommand "my-mysql" {
  import "plugin-check-command"

  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 attribute 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 NodeName {
...
  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 attributes (warning thresholds at 10%, critical thresholds at 5% free disk space).

The custom attribute 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 attributes can be found in this chapter.

Command Arguments

By defining a check command line using the command attribute Icinga 2 will resolve all macros in the static string or array. Sometimes it is required to extend the arguments list based on a met condition evaluated at command execution. Or making arguments optional -- only set if the macro value can be resolved by Icinga 2.

object CheckCommand "check_http" {
  import "plugin-check-command"

  command = [ PluginDir + "/check_http" ]

  arguments = {
    "-H" = "$http_vhost$"
    "-I" = "$http_address$"
    "-u" = "$http_uri$"
    "-p" = "$http_port$"
    "-S" = {
      set_if = "$http_ssl$"
    }
    "--sni" = {
      set_if = "$http_sni$"
    }
    "-a" = {
      value = "$http_auth_pair$"
      description = "Username:password on sites with basic authentication"
    }
    "--no-body" = {
      set_if = "$http_ignore_body$"
    }
    "-r" = "$http_expect_body_regex$"
    "-w" = "$http_warn_time$"
    "-c" = "$http_critical_time$"
    "-e" = "$http_expect$"
  }

  vars.http_address = "$address$"
  vars.http_ssl = false
  vars.http_sni = false
}

The example shows the check_http check command defining the most common arguments. Each of them is optional by default and will be omitted if the value is not set. For example, if the service calling the check command does not have vars.http_port set, it won't get added to the command line.

If the vars.http_ssl custom attribute is set in the service, host or command object definition, Icinga 2 will add the -S argument based on the set_if numeric value to the command line. String values are not supported.

If the macro value cannot be resolved, Icinga 2 will not add the defined argument to the final command argument array. Empty strings for macro values won't omit the argument.

That way you can use the check_http command definition for both, with and without SSL enabled checks saving you duplicated command definitions.

Details on all available options can be found in the CheckCommand object definition.

Environment Variables

The env command object attribute specifies a list of environment variables with values calculated from either runtime macros or custom attributes 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-health" {
  import "plugin-check-command"

  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 = "$mysql_pass$"
}

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.

NotificationCommand objects require the ITL template plugin-notification-command to support native plugin-based notifications.

Note

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

Below is an example using runtime macros from Icinga 2 (such as $service.output$ for the current check output) sending an email to the user(s) associated with the notification itself ($user.email$).

If you want to specify default values for some of the custom attribute definitions, you can add a vars dictionary as shown for the CheckCommand object.

object NotificationCommand "mail-service-notification" {
  import "plugin-notification-command"

  command = [ SysconfDir + "/icinga2/scripts/mail-notification.sh" ]

  env = {
    NOTIFICATIONTYPE = "$notification.type$"
    SERVICEDESC = "$service.name$"
    HOSTALIAS = "$host.display_name$"
    HOSTADDRESS = "$address$"
    SERVICESTATE = "$service.state$"
    LONGDATETIME = "$icinga.long_date_time$"
    SERVICEOUTPUT = "$service.output$"
    NOTIFICATIONAUTHORNAME = "$notification.author$"
    NOTIFICATIONCOMMENT = "$notification.comment$"
	HOSTDISPLAYNAME = "$host.display_name$"
    SERVICEDISPLAYNAME = "$service.display_name$"
    USEREMAIL = "$user.email$"
  }
}

The command attribute in the mail-service-notification command refers to the following shell script. The macros specified in the env array are exported as environment variables and can be used in the notification script:

#!/usr/bin/env bash
template=$(cat <<TEMPLATE
***** Icinga  *****

Notification Type: $NOTIFICATIONTYPE

Service: $SERVICEDESC
Host: $HOSTALIAS
Address: $HOSTADDRESS
State: $SERVICESTATE

Date/Time: $LONGDATETIME

Additional Info: $SERVICEOUTPUT

Comment: [$NOTIFICATIONAUTHORNAME] $NOTIFICATIONCOMMENT
TEMPLATE
)

/usr/bin/printf "%b" $template | mail -s "$NOTIFICATIONTYPE - $HOSTDISPLAYNAME - $SERVICEDISPLAYNAME is $SERVICESTATE" $USEREMAIL

Note

This example is for exim only. Requires changes for sendmail and other MTAs.

While it's possible to specify the 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.

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 using 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 vars. Runtime macros such as $service.state_type$ and $service.state$ will be processed by Icinga 2 helping on fine-granular events being triggered.

If you are using 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 requiring an immediate restart via event command, or if an application is locked and requires a restart upon detection.

EventCommand objects require the ITL template plugin-event-command to support native plugin based checks.

Use Event Commands to Restart Service Daemon

The following example will trigger a restart of the httpd daemon via ssh when the http service check fails. If the service state is OK, it will not trigger any event action.

Requirements:

• ssh connection
• icinga user with public key authentication
• icinga user with sudo permissions for restarting 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:

/* pass event commands through ssh */
object EventCommand "event_by_ssh" {
  import "plugin-event-command"

  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 attribute 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 /etc/init.d/$event_by_ssh_service$ restart"
}

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.

object Service "http" {
  import "generic-service"
  host_name = "remote-http-host"
  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"
}

Each host with this service then must define the httpd_name custom attribute (for example generated from your cmdb):

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

  vars.httpd_name = "apache2"
}

You can testdrive this example by manually stopping the httpd daemon on your remote-http-host. Enable the debuglog feature and tail the /var/log/icinga2/debug.log file.

Remote Host Terminal:

# date; service apache2 status
Mon Sep 15 18:57:39 CEST 2014
Apache2 is running (pid 23651).
# date; service apache2 stop
Mon Sep 15 18:57:47 CEST 2014
[ ok ] Stopping web server: apache2 ... waiting .

Icinga 2 Host Terminal:

[2014-09-15 18:58:32 +0200] notice/Process: Running command '/usr/lib64/nagios/plugins/check_http' '-I' '192.168.1.100': PID 32622
[2014-09-15 18:58:32 +0200] notice/Process: PID 32622 ('/usr/lib64/nagios/plugins/check_http' '-I' '192.168.1.100') terminated with exit code 2
[2014-09-15 18:58:32 +0200] notice/Checkable: State Change: Checkable remote-http-host!http soft state change from OK to CRITICAL detected.
[2014-09-15 18:58:32 +0200] notice/Checkable: Executing event handler 'event_by_ssh_restart_service' for service 'remote-http-host!http'
[2014-09-15 18:58:32 +0200] notice/Process: Running command '/usr/lib64/nagios/plugins/check_by_ssh' '-C' 'test 2 -gt 0 && sudo /etc/init.d/apache2 restart' '-H' '192.168.1.100': PID 32623
[2014-09-15 18:58:33 +0200] notice/Process: PID 32623 ('/usr/lib64/nagios/plugins/check_by_ssh' '-C' 'test 2 -gt 0 && sudo /etc/init.d/apache2 restart' '-H' '192.168.1.100') terminated with exit code 0

Remote Host Terminal:

# date; service apache2 status
Mon Sep 15 18:58:44 CEST 2014
Apache2 is running (pid 24908).

Dependencies

Icinga 2 uses host and service Dependency objects for determing 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 ]

Rephrased: 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 is_reachable attribute in for example DB IDO.

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 implicitely 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"
}

Apply Dependencies based on Custom Attributes

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 attributes (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 attribute 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 attribute 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 classic 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.

The following configuration defines two nrpe based service checks nrpe-load and nrpe-disk applied to the nrpe-server. The health check is defined as nrpe-health service.

apply Service "nrpe-health" {
  import "generic-service"
  check_command = "nrpe"
  assign where match("nrpe-*", host.name)
}

apply Service "nrpe-load" {
  import "generic-service"
  check_command = "nrpe"
  vars.nrpe_command = "check_load"
  assign where match("nrpe-*", host.name)
}

apply Service "nrpe-disk" {
  import "generic-service"
  check_command = "nrpe"
  vars.nrpe_command = "check_disk"
  assign where match("nrpe-*", host.name)
}

object Host "nrpe-server" {
  import "generic-host"
  address = "192.168.1.5"
}

apply Dependency "disable-nrpe-checks" to Service {
  parent_service_name = "nrpe-health"

  states = [ OK ]
  disable_checks = true
  disable_notifications = true
  assign where service.check_command == "nrpe"
  ignore where service.name == "nrpe-health"
}

The disable-nrpe-checks dependency is applied to all services on the nrpe-service host using the nrpe check_command attribute but not the nrpe-health service itself.