# Executors

Executors are used by minion to execute module functions. Executors can be used to modify the functions behavior, do any pre-execution steps or execute in a specific way like sudo executor.

Executors could be passed as a list and they will be used one-by-one in the order. If an executor returns `None` the next one will be called. If an executor returns non-`None` the execution sequence is terminated and the returned value is used as a result. It's a way executor could control modules execution working as a filter. Note that executor could actually not execute the function but just do something else and return `None` like `splay` executor does. In this case some other executor have to be used as a final executor that will actually execute the function. See examples below.

Executors list could be passed by minion config file in the following way:

    module_executors:
      - splay
      - direct_call
    splaytime: 30

The same could be done by command line:

    salt -t 40 --module-executors='[splay, direct_call]' --executor-opts='{splaytime: 30}' '*' test.version

And the same command called via netapi will look like this:

    curl -sSk https://localhost:8000 \
        -H 'Accept: application/x-yaml' \
        -H 'X-Auth-Token: 697adbdc8fe971d09ae4c2a3add7248859c87079' \
        -H 'Content-type: application/json' \
        -d '[{
            "client": "local",
            "tgt": "*",
            "fun": "test.version",
            "module_executors": ["splay", "direct_call"],
            "executor_opts": {"splaytime": 10}
            }]'

See also

The full list of executors

## Writing Salt Executors

A Salt executor is written in a similar manner to a Salt execution module. Executor is a python module placed into the `executors` folder and containing the `execute` function with the following signature:

    def execute(opts, data, func, args, kwargs): ...

Where the args are:

`opts`:

  Dictionary containing the minion configuration options

`data`:

  Dictionary containing the load data including `executor_opts` passed via cmdline/API.

`func`, `args`, `kwargs`:

  Execution module function to be executed and its arguments. For instance the simplest `direct_call` executor just runs it as `func(*args, **kwargs)`.

`Returns`:

  `None` if the execution sequence must be continued with the next executor. Error string or execution result if the job is done and execution must be stopped.

Specific options could be passed to the executor via minion config or via `executor_opts` argument. For instance to access `splaytime` option set by minion config executor should access `opts.get('splaytime')`. To access the option set by commandline or API `data.get('executor_opts', {}).get('splaytime')` should be used. So if an option is safe and must be accessible by user executor should check it in both places, but if an option is unsafe it should be read from the only config ignoring the passed request data.

There is also a function named `all_missing_func` which the name of the `func` is passed, which can be used to verify if the command should still be run, even if it is not loaded in minion_mods.