Puppet - Environment

In software development and delivery model, there are different kind of testing environments which are used for testing a particular product or a service. As a standard practice, there are mainly three kind of environments as development, testing and production, wherein each of them have their own set configuration.

Puppet supports the management of multiple environment along the same line as Ruby on Rails. The key factor behind the creation of these environments is providing an easy mechanism for managing at different levels of SLA agreement. In some cases, the machine always needs to be up without any tolerance and use of old software. Wherein other environments are up-to-date and are used for testing purposes. They are used for upgrades for more important machines.

Puppet recommends to stick with the standard production, testing, and development environment configuration, however, here it even provides the user with a leverage of creating custom environments as per requirement.

Environment Goal

The main goal of setup split by an environment, is that Puppet can have different sources for modules and manifests. One can then test the changes in configuration in the testing environment without impacting the production nodes. These environments can also be used to deploy infrastructure on different sources of network.

Using the Environment on Puppet Master

The point of an environment is to test which manifest, module, template of the file needs to be send to the client. Thus, Puppet must be configured to provide environment-specific source for these information.

Puppet environments are implemented simply by adding the pre-environment sections to the server’s puppet.conf and choosing different configuration source for each environment. These pre-environment sections are then used in preference to the main section.

[main] 
manifest = /usr/testing/puppet/site.pp 
modulepath = /usr/testing/puppet/modules 
[development] 
manifest = /usr/testing/puppet/development/site.pp 
modulepath = /usr/testing/puppet/development/modules

In the above code, any client in the development environment will use the site.pp manifest file located in the directory /usr/share/puppet/development and Puppet will search for any module in /usr/share/puppet/development/modules directory.

Running Puppet with or without any environment would default to site.pp file and the directory specified in the manifest and modulepath values in the main configuration section.

There are only few configurations which actually makes sense to be configured preenvironment, and all of those parameters revolve around specifying what files to use to compile a client’s configuration.

Following are the parameters.

Modulepath − In Puppet, as a basic standard mode it’s best to have a standard module directory that all environment share and then a pre-environment directory where the custom module can be stored. Module path is the location where Puppet looks for all the environment related configuration files.
Templatedir − Template directory is the location where all the versions of related templates are saved. The module should be preferred to these settings, however it allows one to have different versions of a given template in each environment.
Manifest − This defines which configuration to use as entrypoint script.

With multiple modules, Puppets help in getting the modularity for configurations. One can use multiple environments in Puppet which works much better if one relies largely on modules. It is easier to migrate changes to environments by encapsulating changes in the module. File server uses an environment specific module path; if one does file serving from modules, instead of separate mounted directories, this environment will be able to get environment-specific files and finally the current environment will also be available in $environment variable within the manifest file.

Setting the Clients Environment

All the configurations related to environment configuration are done on puppet.conf file. To specify which environment the Puppet client should use, one can specify a value for the environment configuration variable in client’s puppet.conf file.

[puppetd] 
environment = Testing

The above definition in configuration file defines which environment the configuration file is in our case it is testing.

One can also specify this on the command line using −

#puppetd -–environment = testing

Alternatively, Puppet also supports the use of dynamic values in environment configuration. Rather than defining the static values, the developer has a leverage to create custom facts that creates client environment based upon some other client attributes or an external data source. The preferred way of doing it is using a custom tool. These tools are capable of specifying a node’s environment and are generally much better at specifying node information.

Puppet Search Path

Puppet uses a simple search path to determine which configuration needs to be applied on the target machine. In the same way, search path in Puppet is very useful when it is trying to pick up appropriate values which needs to be applied. There are multiple locations as listed below where Puppet searches for the values which needs to be applied.

Value specified in the command line
Values specified in an environment-specific section
Values specified in an executable-specific section
Values specified in the main section