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10-How-it-works.md

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How it works

This chapter wants to give you some basic understanding off how the Director works with your Icinga installation. At least once you start to work with satellite zones it might be worth to give this a read.

How your configuration is going to be rendered

First of all, the Director doesn't write to /etc/icinga2. That's where you keep to store your manual configuration and that's where you are required to do the basic config tasks required to get Icinga 2 ready for the Director.

The Director uses the Icinga 2 API to ship the configuration. It does so by shipping full config packages, it does not deal with single objects. This makes deployments much faster. It also makes it easier to eventually use Director in parallel with manual configuration or configuration shipped by other tools.

Internally, Icinga 2 manages part of its configuration in its var/lib directory. This is usually to be found in /var/lib/icinga2. Config packages are stored to /var/lib/icinga2/api/packages once shipped through the API. So as soon as you deployed your first configuration with the Director, there will be a new timestamped subdirectory containing the new configuration.

Those subdirectories are called stages. You'll often see more than one of them. When a new config is deployed, Icinga 2 tries to restart with that new stage. In case it fails, Icinga 2 will keep running with the former configuration. When it succeeds, it will terminate the old process and keep running with the new configuration.

In either scenario, it writes an exit code and its startup log to the corresponding stage directory. This allows the Director to check back later on to fetch this information. That's why you see all those nice startup log outputs along with your deployment history in your frontend.

The configuration in such a stage directory is structured like your Icinga 2 config directory in /etc: there is a conf.d and a zones.d subdirectory. In zones.d Director will create a subdirectory for each Zone it wants to deploy config to.

Please note that those zones.d subdirectories are subject to config sync. To get them syncronized to other nodes, the following must be true for them:

  • they must have a zone definition for that zone in their local config
  • they must make part of your deployment endpoints zone or be a direct or indirect subzone of that one
  • the accept_config setting must be true in their ApiListener object definition

The director does not try to create additional zones your nodes do not know about. In a distributed environment it is essential that the Director can ship parts of the configuration to specific zones and other parts to a global zone. The name of its preferred global zone is currently hardcoded to director-global. Please make sure that such a zone exists on all involved nodes that should get config from the Director in a direct or indirect way:

object Zone "director-global" {
  global = true
}

Zone membership handling

Mostly you do not need to care much about Zones when working with the Director. In case you have no Satellite node, you wouldn't even notice their existence.

You are not required to deal with Agent Zones, as the Director does this for you. Please refer to Working with agents for related examples.

Currently the GUI does not allow you to set the zone property on single objects. You can circumvent this through the Director's REST API, with Sync rules and through the CLI. However, that shouldn't be part of your normal workflow. So if this restriction causes trouble with what you want to build please let us know. Explain your scenario, make us understand what you want to achieve.

We think of this restriction being a good idea, as it makes things easier for most people. That doesn't mean that we would refuse to change our mind on this. At least not if you come up with a very good reasonable use case.

Object rendering

This chapter explains where the Director renders which config object to.

  • Most objects are rendered to the master zone per default
  • Templates, commands and apply rules are rendered to the global zone
  • Objects with a zone property are rendered to that zone, even if they inherited that property
  • Host objects configured as an Agent are rendered to the master zone, as Director configures them as a Command Execution Bridge
  • Agents with a zone property respect that setting
  • Every command is rendered to the global zone per default