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59 lines
2.3 KiB
ReStructuredText
59 lines
2.3 KiB
ReStructuredText
Periodic Taskgraphs
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===================
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The cron functionality allows in-tree scheduling of task graphs that run
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periodically, instead of on a push.
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Cron.yml
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--------
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In the root of the Gecko directory, you will find `.cron.yml`. This defines
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the periodic tasks ("cron jobs") run for Gecko. Each specifies a name, what to
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do, and some parameters to determine when the cron job should occur.
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See ``taskcluster/taskgraph/cron/schema.py`` for details on the format and
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meaning of this file.
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How It Works
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------------
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The `TaskCluster Hooks Service <https://tools.taskcluster.net/hooks>`_ has a
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hook configured for each repository supporting periodic task graphs. The hook
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runs every 15 minutes, and the resulting task is referred to as a "cron task".
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That cron task runs `./mach taskgraph cron` in a checkout of the Gecko source
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tree.
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The mach subcommand reads ``.cron.yml``, then consults the current time
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(actually the time the cron task was created, rounded down to the nearest 15
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minutes) and creates tasks for any cron jobs scheduled at that time.
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Each cron job in ``.cron.yml`` specifies a ``job.type``, corresponding to a
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function responsible for creating TaskCluster tasks when the job runs.
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Decision Tasks
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..............
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For ``job.type`` "decision-task", tasks are created based on
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``.taskcluster.yml`` just like the decision tasks that result from a push to a
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repository. They run with a distinct ``taskGroupId``, and are free to create
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additional tasks comprising a task graph.
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Scopes
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------
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The cron task runs with the sum of all cron job scopes for the given repo. For
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example, for the "sequoia" project, the scope would be
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``assume:repo:hg.mozilla.org/projects/sequoia:cron:*``. Each cron job creates
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tasks with scopes for that particular job, by name. For example, the
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``check-frob`` cron job on that repo would run with
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``assume:repo:hg.mozilla.org/projects/sequoia:cron:check-frob``.
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.. important::
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The individual cron scopes are a useful check to ensure that a job is not
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accidentally doing something it should not, but cannot actually *prevent* a
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job from using any of the scopes afforded to the cron task itself (the
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``..cron:*`` scope). This is simply because the cron task runs arbitrary
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code from the repo, and that code can be easily modified to create tasks
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with any scopes that it posesses.
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