# Mailman runner control

Mailman has a number of runner subprocesses which perform long-running tasks such as listening on an LMTP port, processing REST API requests, or processing messages in a queue directory. In normal operation, the `mailman` command is used to start, stop and manage the runners. This is just a wrapper around the real master watcher, which handles runner starting, stopping, exiting, and log file reopening.

    >>> from mailman.testing.helpers import TestableMaster

Start the master in a sub-thread.

    >>> master = TestableMaster()
    >>> master.start()

There should be a process id for every runner that claims to be startable.

    >>> from lazr.config import as_boolean
    >>> startable_runners = [conf for conf in config.runner_configs
    ...                      if as_boolean(conf.start)]
    >>> len(list(master.runner_pids)) == len(startable_runners)
    True

Now verify that all the runners are running.

    >>> import os

    # This should produce no output.
    >>> for pid in master.runner_pids:
    ...     os.kill(pid, 0)

Stop the master process, which should also kill (and not restart) the child runner processes.

    >>> master.stop()

None of the children are running now.

    >>> import errno
    >>> from contextlib import suppress
    >>> for pid in master.runner_pids:
    ...     with suppress(ProcessLookupError):
    ...         os.kill(pid, 0)
    ...         print('Process did not exit:', pid)