diff --git a/docs/index.rst b/docs/index.rst index bf185cb..68f8272 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -1,170 +1,170 @@ .. _swh-scheduler: Software Heritage - Job scheduler ================================= Task manager for asynchronous/delayed tasks, used for both recurrent (e.g., listing a forge, loading new stuff from a Git repository) and one-off activities (e.g., loading a specific version of a source package). Description ----------- This module provides a scheduler service for the Software Heritage platform. It allows to define tasks with a number of properties. In this documentation, we will call these swh-tasks to prevent confusion. These swh-tasks are stored in a database, and a HTTP-based RPC service is provided to create or find existing swh-task declarations. The execution model for these swh-tasks is using Celery. Thus, each swh-task type defined in the database must have a (series of) celery worker capable of executing such a swh-task. Then a number of services are also provided to manage the scheduling of these swh-tasks as Celery tasks. -The `scheduler-runner` service is a daemon that regularly looks for swh-tasks +The ``scheduler-runner`` service is a daemon that regularly looks for swh-tasks in the database that should be scheduled. For each of the selected swh-task, a Celery task is instantiated. -The `scheduler-listener` service is a daemon that listen to the Celery event +The ``scheduler-listener`` service is a daemon that listen to the Celery event bus and maintain scheduled swh-tasks workflow status. SWH Task Model ~~~~~~~~~~~~~~ Each swh-task-type is the declaration of a type of swh-task. Each swh-task-type have the following fields: -- `type`: Name of the swh-task type; can be anything but must be unique, -- `description`: Human-readable task description -- `backend_name`: Name of the task in the job-running backend, -- `default_interval`: Default interval for newly scheduled tasks, -- `min_interval`: Minimum interval between two runs of a task, -- `max_interval`: Maximum interval between two runs of a task, -- `backoff_factor`: Adjustment factor for the backoff between two task runs, -- `max_queue_length`: Maximum length of the queue for this type of tasks, -- `num_retries`: Default number of retries on transient failures, -- `retry_delay`: Retry delay for the task, - -Existing swh-task-types can be listed using the `swh scheduler` command line +- ``type``: Name of the swh-task type; can be anything but must be unique, +- ``description``: Human-readable task description +- ``backend_name``: Name of the task in the job-running backend, +- ``default_interval``: Default interval for newly scheduled tasks, +- ``min_interval``: Minimum interval between two runs of a task, +- ``max_interval``: Maximum interval between two runs of a task, +- ``backoff_factor``: Adjustment factor for the backoff between two task runs, +- ``max_queue_length``: Maximum length of the queue for this type of tasks, +- ``num_retries``: Default number of retries on transient failures, +- ``retry_delay``: Retry delay for the task, + +Existing swh-task-types can be listed using the ``swh scheduler`` command line tool:: $ swh scheduler task-type list Known task types: check-deposit: Pre-checking deposit step before loading into swh archive index-fossology-license: Fossology license indexer task load-git: Update an origin of type git load-hg: Update an origin of type mercurial You can see the details of a swh-task-type:: $ swh scheduler task-type list -v -t load-git Known task types: load-git: swh.loader.git.tasks.UpdateGitRepository Update an origin of type git interval: 64 days, 0:00:00 [12:00:00, 64 days, 0:00:00] backoff_factor: 2.0 max_queue_length: 5000 num_retries: None retry_delay: None An swh-task is an 'instance' of such a swh-task-type, and consists in: -- `arguments`: Arguments passed to the underlying job scheduler, -- `next_run`: Next run of this task should be run on or after that time, -- `current_interval`: Interval between two runs of this task, taking into +- ``arguments``: Arguments passed to the underlying job scheduler, +- ``next_run``: Next run of this task should be run on or after that time, +- ``current_interval``: Interval between two runs of this task, taking into account the backoff factor, -- `policy`: Whether the task is "one-shot" or "recurring", -- `retries_left`: Number of "short delay" retries of the task in case of +- ``policy``: Whether the task is "one-shot" or "recurring", +- ``retries_left``: Number of "short delay" retries of the task in case of transient failure, -- `priority`: Priority of the task, -- `id`: Internal task identifier, -- `type`: References task_type table, -- `status`: Task status ( among "next_run_not_scheduled", "next_run_scheduled", +- ``priority``: Priority of the task, +- ``id``: Internal task identifier, +- ``type``: References task_type table, +- ``status``: Task status ( among "next_run_not_scheduled", "next_run_scheduled", "completed", "disabled"). So a swh-task consist basically in: - a set of parameters defining how the scheduling of the swh-task is handled, - a set of parameters to specify the retry policy in case of transient failure upon execution, -- a set of parameters that defines the job to be done (`bakend_name` + - `arguments`). +- a set of parameters that defines the job to be done (``bakend_name`` + + ``arguments``). You can list pending swh-tasks (tasks that are to be scheduled ASAP):: $ swh scheduler task list-pending load-git --limit 2 Found 1 load-git tasks Task 9052257 Next run: 15 days ago (2019-06-25 10:35:10+00:00) Interval: 2 days, 0:00:00 Type: load-git Policy: recurring Args: 'https://github.com/turtl/mobile' Keyword args: Looking for existing swh-task can be done via the command line tool:: $ swh scheduler task list -t load-hg --limit 2 Found 2 tasks Task 168802702 Next run: in 4 hours (2019-07-10 17:56:48+00:00) Interval: 1 day, 0:00:00 Type: load-hg Policy: recurring Status: next_run_not_scheduled Priority: Args: 'https://bitbucket.org/kepung/pypy' Keyword args: Task 169800445 Next run: in a month (2019-08-10 17:54:24+00:00) Interval: 32 days, 0:00:00 Type: load-hg Policy: recurring Status: next_run_not_scheduled Priority: Args: 'https://bitbucket.org/lunixbochs/pypy-1' Keyword args: Writing a new worker for a new swh-task-type -------------------------------------------- When you want to add a new swh-task-type, you need a celery worker backend capable of executing this new task-type instances. Celery workers for swh-scheduler based tasks should be started using the Celery -app in `swh.scheduler.celery_config`. This later, among other things, provides +app in ``swh.scheduler.celery_config``. This later, among other things, provides a loading mechanism for task types based on pkg_resources declared plugins under -the `[swh.workers]` entry point. +the ``[swh.workers]`` entry point. TODO: add a fully working example of a dumb task. Reference Documentation ----------------------- .. toctree:: :maxdepth: 2 cli simulator /apidoc/swh.scheduler