Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 152 insertions, 0 deletions

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+Task Generation
+===============
+
+Many selectors (including ``chooser``, ``coverage`` and ``fuzzy``) source their available tasks
+directly from the :ref:`taskgraph <TaskCluster Task-Graph Generation>` module by building the taskgraph
+locally. This means that the list of available tasks will never be stale. While this is very
+powerful, it comes with a large enough performance cost to get annoying (around twenty seconds).
+
+The result of the taskgraph generation will be cached, so this penalty will only be incurred
+whenever a file in the ``/taskcluster`` directory is modified. Unfortunately this directory changes
+pretty frequently, so developers can expect to rebuild the cache each time they pull in
+``mozilla-central``. Developers who regularly work on ``/taskcluster`` can expect to rebuild even
+more frequently.
+
+
+Configuring Watchman
+--------------------
+
+It's possible to bypass this penalty completely by using the file watching service `watchman`_. If
+you use the ``fsmonitor`` mercurial extension, you already have ``watchman`` installed.
+
+.. note::
+
+    If you aren't using `fsmonitor`_ but end up installng watchman anyway, you
+    might as well enable it for a faster Mercurial experience.
+
+Otherwise, `install watchman`_. If using Linux you'll likely run into the `inotify limits`_ outlined
+on that page due to the size of ``mozilla-central``. You can `read this page`_ for more information
+on how to bump the limits permanently.
+
+Next run the following commands:
+
+.. code-block:: shell
+
+    $ cd path/to/mozilla-central
+    $ watchman watch .
+    $ watchman -j < tools/tryselect/watchman.json
+
+You should see output like:
+
+.. code-block:: json
+
+    {
+        "triggerid": "rebuild-taskgraph-cache",
+        "disposition": "created",
+        "version": "20200920.192359.0"
+    }
+
+That's it. Now anytime a file under ``/taskcluster`` is modified (either by your editor, or by
+updating version control), the taskgraph cache will be rebuilt in the background, allowing you to
+skip the wait the next time you run ``mach try``.
+
+.. note::
+
+    Watchman triggers are persistent and don't need to be added more than once.
+    See `Managing Triggers`_ for how to remove a trigger.
+
+You can test that everything is working by running these commands:
+
+.. code-block:: shell
+
+    $ statedir=`mach python -c "from mach.util import get_state_dir; print(get_state_dir(specific_to_topsrcdir=True))"`
+    $ rm -rf $statedir/cache/taskgraph
+    $ touch taskcluster/mach_commands.py
+    # wait a minute for generation to trigger and finish
+    $ ls $statedir/cache/taskgraph
+
+If the ``target_task_set`` file exists, you are good to go. If not you can look at the ``watchman``
+log to see if there were any errors. This typically lives somewhere like
+``/usr/local/var/run/watchman/$USER-state/log``. In this case please file a bug under ``Firefox
+Build System :: Try`` and include the relevant portion of the log.
+
+
+Running Watchman on Startup
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Watchman is both a client and a service all in one. When running a ``watchman`` command, the client
+binary will start the service in the background if it isn't running. This means on reboot the
+service won't be running and you'll need to start the service each time by invoking the client
+binary (e.g by running ``watchman version``).
+
+If you'd like this to happen automatically, you can use your favourite platform specific way of
+running commands at startup (``crontab``, ``rc.local``, etc.). Watchman stores separate state for
+each user, so be sure you run the command as the user that set up the triggers.
+
+Setting up a systemd Service
+++++++++++++++++++++++++++++
+
+If ``systemd`` is an option you can create a service:
+
+.. code-block:: ini
+
+    [Unit]
+    Description=Watchman for %i
+    After=network.target
+
+    [Service]
+    Type=simple
+    User=%i
+    ExecStart=/usr/local/bin/watchman --log-level 1 watch-list -f
+    ExecStop=/usr/local/bin/watchman shutdown-server
+
+    [Install]
+    WantedBy=multi-user.target
+
+Save this to a file called ``/etc/systemd/system/watchman@.service``. Then run:
+
+.. code-block:: shell
+
+    $ sudo systemctl enable watchman@$USER.service
+    $ sudo systemctl start watchman@$USER.service
+
+The next time you reboot, the watchman service should start automatically.
+
+
+Managing Triggers
+~~~~~~~~~~~~~~~~~
+
+When adding a trigger watchman writes it to disk. Typically it'll be a path similar to
+``/usr/local/var/run/watchman/$USER-state/state``. While editing that file by hand would work, the
+watchman binary provides an interface for managing your triggers.
+
+To see all directories you are currently watching:
+
+.. code-block:: shell
+
+    $ watchman watch-list
+
+To view triggers that are active in a specified watch:
+
+.. code-block:: shell
+
+    $ watchman trigger-list <path>
+
+To delete a trigger from a specified watch:
+
+.. code-block:: shell
+
+    $ watchman trigger-del <path> <name>
+
+In the above two examples, replace ``<path>`` with the path of the watch, presumably
+``mozilla-central``. Using ``.`` works as well if that is already your working directory. For more
+information on managing triggers and a reference of other commands, see the `official docs`_.
+
+
+.. _watchman: https://facebook.github.io/watchman/
+.. _fsmonitor: https://www.mercurial-scm.org/wiki/FsMonitorExtension
+.. _install watchman: https://facebook.github.io/watchman/docs/install.html
+.. _inotify limits: https://facebook.github.io/watchman/docs/install.html#linux-inotify-limits
+.. _read this page: https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers
+.. _this hint: https://github.com/facebook/watchman/commit/2985377eaf8c8538b28fae9add061b67991a87c2
+.. _official docs: https://facebook.github.io/watchman/docs/cmd/trigger.html