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Advanced Topics

This chapter covers a number of advanced topics. If you're new to Icinga you can safely skip over things you're not interested in.

Downtimes

Downtimes can be scheduled for planned server maintenance or any other targetted service outage you are aware of in advance.

Downtimes will suppress any notifications, and may trigger other downtimes too. If the downtime was set by accident, or the duration exceeds the maintenance, you can manually cancel the downtime. Planned downtimes will also be taken into account for SLA reporting tools calculating the SLAs based on the state and downtime history.

Multiple downtimes for a single object may overlap. This is useful when you want to extend your maintenance window taking longer than expected. If there are multiple downtimes triggered for one object, the overall downtime depth will be greater than 1.

If the downtime was scheduled after the problem changed to a critical hard state triggering a problem notification, and the service recovers during the downtime window, the recovery notification won't be suppressed.

Fixed and Flexible Downtimes

A fixed downtime will be activated at the defined start time, and removed at the end time. During this time window the service state will change to NOT-OK and then actually trigger the downtime. Notifications are suppressed and the downtime depth is incremented.

Common scenarios are a planned distribution upgrade on your linux servers, or database updates in your warehouse. The customer knows about a fixed downtime window between 23:00 and 24:00. After 24:00 all problems should be alerted again. Solution is simple - schedule a fixed downtime starting at 23:00 and ending at 24:00.

Unlike a fixed downtime, a flexible downtime will be triggered by the state change in the time span defined by start and end time, and then last for the specified duration in minutes.

Imagine the following scenario: Your service is frequently polled by users trying to grab free deleted domains for immediate registration. Between 07:30 and 08:00 the impact will hit for 15 minutes and generate a network outage visible to the monitoring. The service is still alive, but answering too slow to Icinga 2 service checks. For that reason, you may want to schedule a downtime between 07:30 and 08:00 with a duration of 15 minutes. The downtime will then last from its trigger time until the duration is over. After that, the downtime is removed (may happen before or after the actual end time!).

Scheduling a downtime

This can either happen through a web interface or by sending an external command to the external command pipe provided by the ExternalCommandListener configuration.

Fixed downtimes require a start and end time (a duration will be ignored). Flexible downtimes need a start and end time for the time span, and a duration independent from that time span.

Triggered Downtimes

This is optional when scheduling a downtime. If there is already a downtime scheduled for a future maintenance, the current downtime can be triggered by that downtime. This renders useful if you have scheduled a host downtime and are now scheduling a child host's downtime getting triggered by the parent downtime on NOT-OK state change.

Recurring Downtimes

ScheduledDowntime objects can be used to set up recurring downtimes for services.

Example:

apply ScheduledDowntime "backup-downtime" to Service {
  author = "icingaadmin"
  comment = "Scheduled downtime for backup"

  ranges = {
    monday = "02:00-03:00"
    tuesday = "02:00-03:00"
    wednesday = "02:00-03:00"
    thursday = "02:00-03:00"
    friday = "02:00-03:00"
    saturday = "02:00-03:00"
    sunday = "02:00-03:00"
  }

  assign where "backup" in service.groups
}

Comments

Comments can be added at runtime and are persistent over restarts. You can add useful information for others on repeating incidents (for example "last time syslog at 100% cpu on 17.10.2013 due to stale nfs mount") which is primarly accessible using web interfaces.

Adding and deleting comment actions are possible through the external command pipe provided with the ExternalCommandListener configuration. The caller must pass the comment id in case of manipulating an existing comment.

Acknowledgements

If a problem is alerted and notified you may signal the other notification recipients that you are aware of the problem and will handle it.

By sending an acknowledgement to Icinga 2 (using the external command pipe provided with ExternalCommandListener configuration) all future notifications are suppressed, a new comment is added with the provided description and a notification with the type NotificationFilterAcknowledgement is sent to all notified users.

Expiring Acknowledgements

Once a problem is acknowledged it may disappear from your handled problems dashboard and no-one ever looks at it again since it will suppress notifications too.

This fire-and-forget action is quite common. If you're sure that a current problem should be resolved in the future at a defined time, you can define an expiration time when acknowledging the problem.

Icinga 2 will clear the acknowledgement when expired and start to re-notify if the problem persists.

Time Periods

Time Periods define time ranges in Icinga where event actions are triggered, for example whether a service check is executed or not within the check_period attribute. Or a notification should be sent to users or not, filtered by the period and notification_period configuration attributes for Notification and User objects.

Note

If you are familar with Icinga 1.x - these time period definitions are called legacy timeperiods in Icinga 2.

An Icinga 2 legacy timeperiod requires the ITL provided template legacy-timeperiod.

The TimePeriod attribute ranges may contain multiple directives, including weekdays, days of the month, and calendar dates. These types may overlap/override other types in your ranges dictionary.

The descending order of precedence is as follows:

Calendar date (2008-01-01)
Specific month date (January 1st)
Generic month date (Day 15)
Offset weekday of specific month (2nd Tuesday in December)
Offset weekday (3rd Monday)
Normal weekday (Tuesday)

If you don't set any check_period or notification_period attribute on your configuration objects Icinga 2 assumes 24x7 as time period as shown below.

object TimePeriod "24x7" {
  import "legacy-timeperiod"

  display_name = "Icinga 2 24x7 TimePeriod"
  ranges = {
    "monday"    = "00:00-24:00"
    "tuesday"   = "00:00-24:00"
    "wednesday" = "00:00-24:00"
    "thursday"  = "00:00-24:00"
    "friday"    = "00:00-24:00"
    "saturday"  = "00:00-24:00"
    "sunday"    = "00:00-24:00"
  }
}

If your operation staff should only be notified during workhours create a new timeperiod named workhours defining a work day from 09:00 to 17:00.

object TimePeriod "workhours" {
  import "legacy-timeperiod"

  display_name = "Icinga 2 8x5 TimePeriod"
  ranges = {
    "monday"    = "09:00-17:00"
    "tuesday"   = "09:00-17:00"
    "wednesday" = "09:00-17:00"
    "thursday"  = "09:00-17:00"
    "friday"    = "09:00-17:00"
  }
}

Use the period attribute to assign time periods to Notification and Dependency objects:

object Notification "mail" {
  import "generic-notification"

  host_name = "localhost"

  command = "mail-notification"
  users = [ "icingaadmin" ]
  period = "workhours"
}

Use Functions in Object Configuration

There is a limited scope where functions can be used as object attributes such as:

As value for Custom Attributes
Returning boolean expressions for set_if inside command arguments
Returning a command array inside command objects

The other way around you can create objects dynamically using your own global functions.

Note

Functions called inside command objects share the same global scope as runtime macros. Therefore you can access host custom attributes like host.vars.os, or any other object attribute from inside the function definition used for set_if or command.

Tips when implementing functions:

Use log() to dump variables. You can see the output inside the icinga2.log file depending in your log severity
Use the icinga2 console to test basic functionality (e.g. iterating over a dictionary)
Build them step-by-step. You can always refactor your code later on.

Use Functions in Command Arguments set_if

The set_if attribute inside the command arguments definition in the CheckCommand object definition is primarly used to evaluate whether the command parameter should be set or not.

By default you can evaluate runtime macros for their existance, and if the result is not an empty string the command parameter is passed. This becomes fairly complicated when want to evaluate multiple conditions and attributes.

The following example was found on the community support channels. The user had defined a host dictionary named compellent with the key disks. This was then used inside service apply for rules.

object Host "dict-host" {
  check_command = "check_compellent"
  vars.compellent["disks"] = {
    file = "/var/lib/check_compellent/san_disks.0.json",
    checks = ["disks"]
  }
}

The more significant problem was to only add the command parameter --disk to the plugin call when the dictionary compellent contains the key disks, and omit it if not found.

By defining set_if as abbreviated lambda function and evaluating the host custom attribute compellent containing the disks this problem was solved like this:

object CheckCommand "check_compellent" {
  import "plugin-check-command"
  command   = [ "/usr/bin/check_compellent" ]
  arguments   = {
    "--disks"  = {
      set_if = {{
        var host_vars = host.vars
        log(host_vars)
        var compel = host_vars.compellent
        log(compel)
        compel.contains("disks")
      }}
    }
  }
}

This implementation uses the dictionary type method contains and will fail if host.vars.compellent is not of the type Dictionary. Therefore you can extend the checks using the typeof function.

You can test the types using the icinga2 console:

# icinga2 console
Icinga (version: v2.3.0-193-g3eb55ad)
<1> => srv_vars.compellent["check_a"] = { file="outfile_a.json", checks = [ "disks", "fans" ] }
null
<2> => srv_vars.compellent["check_b"] = { file="outfile_b.json", checks = [ "power", "voltages" ] }
null
<3> => typeof(srv_vars.compellent)
type 'Dictionary'
<4> =>

The more programmatic approach for set_if could look like this:

    "--disks" = {
      set_if = {{
        var srv_vars = service.vars
        if(len(srv_vars) > 0) {
          if (typeof(srv_vars.compellent) == Dictionary) {
            return srv_vars.compellent.contains("disks")
          } else {
            log(LogInformationen, "checkcommand set_if", "custom attribute compellent_checks is not a dictionary, ignoring it.")
            return false
          }
        } else {
          log(LogWarning, "checkcommand set_if", "empty custom attributes")
          return false
        }
      }}
    }

Use Functions as Command Attribute

This comes in handy for NotificationCommands or EventCommands which does not require a returned checkresult including state/output.

The following example was taken from the community support channels. The requirement was to specify a custom attribute inside the notification apply rule and decide which notification script to call based on that.

object User "short-dummy" {
}

object UserGroup "short-dummy-group" {
  assign where user.name == "short-dummy"
}

apply Notification "mail-admins-short" to Host {
   import "mail-host-notification"
   command = "mail-host-notification-test"
   user_groups = [ "short-dummy-group" ]
   vars.short = true
   assign where host.vars.notification.mail
}

The solution is fairly simple: The command attribute is implemented as function returning an array required by the caller Icinga 2. The local variable mailscript sets the default value for the notification scrip location. If the notification custom attribute short is set, it will override the local variable mailscript with a new value. The mailscript variable is then used to compute the final notification command array being returned.

You can omit the log() calls, they only help debugging.

object NotificationCommand "mail-host-notification-test" {
  import "plugin-notification-command"
  command = {{
    log("command as function")
    var mailscript = "mail-host-notification-long.sh"
    if (notification.vars.short) {
       mailscript = "mail-host-notification-short.sh"
    }
    log("Running command")
    log(mailscript)

    var cmd = [ SysconfDir + "/icinga2/scripts/" + mailscript ]
    log(LogCritical, "me", cmd)
    return cmd
  }}

  env = {
  }
}

Access Object Attributes at Runtime

The Object Accessor Functions can be used to retrieve references to other objects by name.

This allows you to access configuration and runtime object attributes. A detailed list can be found here.

Simple cluster example for accessing two host object states and calculating a virtual cluster state and output:

object Host "cluster-host-01" {
  check_command = "dummy"
  vars.dummy_state = 2
  vars.dummy_text = "This host is down."
}

object Host "cluster-host-02" {
  check_command = "dummy"
  vars.dummy_state = 0
  vars.dummy_text = "This host is up."
}

object Host "cluster" {
  check_command = "dummy"
  vars.cluster_nodes = [ "cluster-host-01", "cluster-host-02" ]

  vars.dummy_state = {{
    var up_count = 0
    var down_count = 0
    var cluster_nodes = macro("$cluster_nodes$")

    for (node in cluster_nodes) {
      if (get_host(node).state > 0) {
        down_count += 1
      } else {
        up_count += 1
      }
    }

    if (up_count >= down_count) {
      return 0 //same up as down -> UP
    } else {
      return 1 //something is broken
    }
  }}

  vars.dummy_text = {{
    var output = "Cluster hosts:\n"
    var cluster_nodes = macro("$cluster_nodes$")

    for (node in cluster_nodes) {
      output += node + ": " + get_host(node).last_check_result.output + "\n"
    }

    return output
  }}
}

The following example sets time dependent thresholds for the load check based on the current time of the day compared to the defined time period.

object TimePeriod "backup" {
  import "legacy-timeperiod"

  ranges = {
    monday = "02:00-03:00"
    tuesday = "02:00-03:00"
    wednesday = "02:00-03:00"
    thursday = "02:00-03:00"
    friday = "02:00-03:00"
    saturday = "02:00-03:00"
    sunday = "02:00-03:00"
  }
}

object Host "webserver-with-backup" {
  check_command = "hostalive"
  address = "127.0.0.1"
}

object Service "webserver-backup-load" {
  check_command = "load"
  host_name = "webserver-with-backup"

  vars.load_wload1 = {{
    if (get_time_period("backup").is_inside) {
      return 20
    } else {
      return 5
    }
  }}
  vars.load_cload1 = {{
    if (get_time_period("backup").is_inside) {
      return 40
    } else {
      return 10
    }
  }}
}

Check Result Freshness

In Icinga 2 active check freshness is enabled by default. It is determined by the check_interval attribute and no incoming check results in that period of time.

threshold = last check execution time + check interval

Passive check freshness is calculated from the check_interval attribute if set.

threshold = last check result time + check interval

If the freshness checks are invalid, a new check is executed defined by the check_command attribute.

Check Flapping

The flapping algorithm used in Icinga 2 does not store the past states but calculcates the flapping threshold from a single value based on counters and half-life values. Icinga 2 compares the value with a single flapping threshold configuration attribute named flapping_threshold.

Flapping detection can be enabled or disabled using the enable_flapping attribute.

Volatile Services

By default all services remain in a non-volatile state. When a problem occurs, the SOFT state applies and once max_check_attempts attribute is reached with the check counter, a HARD state transition happens. Notifications are only triggered by HARD state changes and are then re-sent defined by the interval attribute.

It may be reasonable to have a volatile service which stays in a HARD state type if the service stays in a NOT-OK state. That way each service recheck will automatically trigger a notification unless the service is acknowledged or in a scheduled downtime.

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