Runner

Runner is a project that manages starting tasks in a defined order. If tasks fail, the chain can be retried, or halted.

Configuration

Configuration is done with INI style configuration files.

[runner] section

Keys:

• sleep_time: minimum time to wait between retries
• retry_jitter: a random interval, added to sleep_times
• max_tries: how many times to retry before giving up
• halt_task: which task to run to “halt” the process. This could perhaps shut the machine down or terminate the EC2 instance
• task_hook: a command which will run before and after each task, with relevant task stats passed in as a json blob.
• max_time: maximum amount of time a task can run
• interpreter: an explicit interpreter to be used for running tasks (for platforms which do not support hashbangs).

Task Stats:

pre/post task hooks receive task stats as an argument. Task stats is a json blog of the format:

  {
      "task": "the task name",
      "try_num": "the current try count",
      "max_retries": "passed in via the config",
      "result": "passed only to the post hook, the result of a task run."
  }

[env] section

Keys and values in this section are passed into tasks as environment variables

other sections

Configuration for other tasks or purposes can go into their own sections.

Tasks

Tasks are loaded from a task dir. Tasks are run as separate processes.

The return code of a task determines what happens next.

Return code 0 means everything went well, and to continue on to the next task.

Return code 2 means to run the “halt” task, and then stop running tasks and exit runner

Other return codes will cause runner to retry tasks from the beginning.

A special environment variable, "RUNNER_CONFIG_CMD" is always set in the environment that allows tasks to easily access configuration. e.g.

$RUNNER_CONFIG_CMD -g hg.remote

will return the “remote” configuration variable from the “hg” section

Tests

Tests are run via nose Run python setup.py nosetests, or nose manually

Runner also uses doctests Run python -m doctest -v runner.py