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diff --git a/taskcluster/docs/howto/index.rst b/taskcluster/docs/howto/index.rst new file mode 100644 index 0000000000..ab1010666b --- /dev/null +++ b/taskcluster/docs/howto/index.rst @@ -0,0 +1,203 @@ +How Tos +======= + +All of this equipment is here to help you get your work done more efficiently. +However, learning how task-graphs are generated is probably not the work you +are interested in doing. This section should help you accomplish some of the +more common changes to the task graph with minimal fuss. + +Taskgraph's documentation provides many relevant how-to guides: + +.. note:: + + If you come across references to the ``taskgraph`` command, simply prepend + ``./mach`` to the command to make it work in ``mozilla-central``. + +.. toctree:: + + Run Taskgraph Locally <https://taskcluster-taskgraph.readthedocs.io/en/latest/howto/run-locally.html> + Debug Taskgraph <https://taskcluster-taskgraph.readthedocs.io/en/latest/howto/debugging.html> + Use Fetches <https://taskcluster-taskgraph.readthedocs.io/en/latest/howto/use-fetches.html> + Use Docker Images <https://taskcluster-taskgraph.readthedocs.io/en/latest/howto/docker.html> + Create Actions <https://taskcluster-taskgraph.readthedocs.io/en/latest/howto/create-actions.html> + +See Taskgraph's `how-to section`_ for even more guides! + +.. _how-to section: https://taskcluster-taskgraph.readthedocs.io/en/latest/howto/index.html + +Common Changes +-------------- + +Additionally, here are some tips for common changes you wish to make within +``mozilla-central``. + +Changing Test Characteristics +............................. + +First, find the test description. This will be in +``taskcluster/ci/*/tests.yml``, for the appropriate kind (consult +:ref:`kinds`). You will find a YAML stanza for each test suite, and each +stanza defines the test's characteristics. For example, the ``chunks`` +property gives the number of chunks to run. This can be specified as a simple +integer if all platforms have the same chunk count, or it can be keyed by test +platform. For example: + +.. code-block:: yaml + + chunks: + by-test-platform: + linux64/debug: 10 + default: 8 + +The full set of available properties is in +``taskcluster/gecko_taskgraph/transforms/test/__init__.py``. Some other +commonly-modified properties are ``max-run-time`` (useful if tests are being +killed for exceeding maxRunTime) and ``treeherder-symbol``. + +.. note:: + + Android tests are also chunked at the mozharness level, so you will need to + modify the relevant mozharness config, as well. + +Adding a Test Suite +................... + +To add a new test suite, you will need to know the proper mozharness invocation +for that suite, and which kind it fits into (consult :ref:`kinds`). + +Add a new stanza to ``taskcluster/ci/<kind>/tests.yml``, copying from the other +stanzas in that file. The meanings should be clear, but authoritative +documentation is in +``taskcluster/gecko_taskgraph/transforms/test/__init__.py`` should you need +it. The stanza name is the name by which the test will be referenced in try +syntax. + +Add your new test to a test set in ``test-sets.yml`` in the same directory. If +the test should only run on a limited set of platforms, you may need to define +a new test set and reference that from the appropriate platforms in +``test-platforms.yml``. If you do so, include some helpful comments in +``test-sets.yml`` for the next person. + +Greening Up a New Test +...................... + +When a test is not yet reliably green, configuration for that test should not +be landed on integration branches. Of course, you can control where the +configuration is landed! For many cases, it is easiest to green up a test in +try: push the configuration to run the test to try along with your work to fix +the remaining test failures. + +When working with a group, check out a "twig" repository to share among your +group, and land the test configuration in that repository. Once the test is +green, merge to an integration branch and the test will begin running there as +well. + +Adding a New Task +................. + +If you are adding a new task that is not a test suite, there are a number of +options. A few questions to consider: + + * Is this a new build platform or variant that will produce an artifact to + be run through the usual test suites? + + * Does this task depend on other tasks? Do other tasks depend on it? + + * Is this one of a few related tasks, or will you need to generate a large + set of tasks using some programmatic means (for example, chunking)? + + * How is the task actually executed? Mozharness? Mach? + + * What kind of environment does the task require? + +Armed with that information, you can choose among a few options for +implementing this new task. Try to choose the simplest solution that will +satisfy your near-term needs. Since this is all implemented in-tree, it +is not difficult to refactor later when you need more generality. + +Existing Kind +````````````` + +The simplest option is to add your task to an existing kind. This is most +practical when the task "makes sense" as part of that kind -- for example, if +your task is building an installer for a new platform using mozharness scripts +similar to the existing build tasks, it makes most sense to add your task to +the ``build`` kind. If you need some additional functionality in the kind, +it's OK to modify the implementation as necessary, as long as the modification +is complete and useful to the next developer to come along. + +Tasks in the ``build`` kind generate Firefox installers, and the ``test`` kind +will add a full set of Firefox tests for each ``build`` task. + +New Kind +```````` + +The next option to consider is adding a new kind. A distinct kind gives you +some isolation from other task types, which can be nice if you are adding an +experimental kind of task. + +Kinds can range in complexity. The simplest sort of kind uses the transform +loader to read a list of jobs from the ``jobs`` key, and applies the standard +``job`` and ``task`` transforms: + +.. code-block:: yaml + + implementation: taskgraph.task.transform:TransformTask + transforms: + - taskgraph.transforms.job:transforms + - taskgraph.transforms.task:transforms + jobs: + - ..your job description here.. + +Job descriptions are defined and documented in +``taskcluster/gecko_taskgraph/transforms/job/__init__.py``. + +Custom Kind Loader +`````````````````` + +If your task depends on other tasks, then the decision of which tasks to create +may require some code. For example, the ``test`` kind iterates over +the builds in the graph, generating a full set of test tasks for each one. This specific +post-build behavior is implemented as a loader defined in ``taskcluster/gecko_taskgraph/loader/test.py``. + +A custom loader is useful when the set of tasks you want to create is not +static but based on something else (such as the available builds) or when the +dependency relationships for your tasks are complex. + +Custom Transforms +````````````````` + +Most loaders apply a series of ":ref:`transforms`" that start with +an initial human-friendly description of a task and end with a task definition +suitable for insertion into a Taskcluster queue. + +Custom transforms can be useful to apply defaults, simplifying the YAML files +in your kind. They can also apply business logic that is more easily expressed +in code than in YAML. + +Transforms need not be one-to-one: a transform can produce zero or more outputs +for each input. For example, the test transforms perform chunking by producing +an output for each chunk of a given input. + +Ideally those transforms will produce job descriptions, so you can use the +existing ``job`` and ``task`` transforms: + +.. code-block:: yaml + + transforms: + - taskgraph.transforms.my_stuff:transforms + - taskgraph.transforms.job:transforms + - taskgraph.transforms.task:transforms + +Try to keep transforms simple, single-purpose and well-documented! + +Custom Run-Using +```````````````` + +If the way your task is executed is unique (so, not a mach command or +mozharness invocation), you can add a new implementation of the job +description's "run" section. Before you do this, consider that it might be a +better investment to modify your task to support invocation via mozharness or +mach, instead. If this is not possible, then adding a new file in +``taskcluster/gecko_taskgraph/transforms/jobs`` with a structure similar to its peers +will make the new run-using option available for job descriptions. |