Dunder Dictionaries

Salt provides several special "dunder" dictionaries as a convenience for Salt development. These include __opts__, __context__, __salt__, and others. This document will describe each dictionary and detail where they exist and what information and/or functionality they provide.

__opts__

Available in

  • All loader modules

The __opts__ dictionary contains all of the options passed in the configuration file for the master or minion.

Note

In many places in salt, instead of pulling raw data from the __opts__ dict, configuration data should be pulled from the salt get functions such as config.get, aka - __salt__['config.get']('foo:bar') The get functions also allow for dict traversal via the : delimiter. Consider using get functions whenever using __opts__ or __pillar__ and __grains__ (when using grains for configuration data)

The configuration file data made available in the __opts__ dictionary is the configuration data relative to the running daemon. If the modules are loaded and executed by the master, then the master configuration data is available, if the modules are executed by the minion, then the minion configuration is available. Any additional information passed into the respective configuration files is made available

__salt__

Available in

  • Execution Modules
  • State Modules
  • Returners
  • Runners
  • SDB Modules

__salt__ contains the execution module functions. This allows for all functions to be called as they have been set up by the salt loader.

__salt__['cmd.run']('fdisk -l')
__salt__['network.ip_addrs']()

Note

When used in runners, __salt__ references other runner modules, and not execution modules.

__grains__

Available in

  • Execution Modules
  • State Modules
  • Returners
  • External Pillar

The __grains__ dictionary contains the grains data generated by the minion that is currently being worked with. In execution modules, state modules and returners this is the grains of the minion running the calls, when generating the external pillar the __grains__ is the grains data from the minion that the pillar is being generated for.

__pillar__

Available in

  • Execution Modules
  • State Modules
  • Returners

The __pillar__ dictionary contains the pillar for the respective minion.

__context__

__context__ exists in state modules and execution modules.

During a state run the __context__ dictionary persists across all states that are run and then is destroyed when the state ends.

When running an execution module __context__ persists across all module executions until the modules are refreshed; such as when saltutil.sync_all or state.apply are executed.

A great place to see how to use __context__ is in the cp.py module in salt/modules/cp.py. The fileclient authenticates with the master when it is instantiated and then is used to copy files to the minion. Rather than create a new fileclient for each file that is to be copied down, one instance of the fileclient is instantiated in the __context__ dictionary and is reused for each file. Here is an example from salt/modules/cp.py:

if not 'cp.fileclient' in __context__:
    __context__['cp.fileclient'] = salt.fileclient.get_file_client(__opts__)

Note

Because __context__ may or may not have been destroyed, always be sure to check for the existence of the key in __context__ and generate the key before using it.