6 There are various caches used by the in-tree tasks. This page attempts to
7 document them and their appropriate use.
9 Caches are essentially isolated filesystems that are persisted between
10 tasks. For example, if 2 tasks run on a worker - one after the other -
11 and both tasks request the same cache, the subsequent task will be
12 able to see files in the cache that were created by the first task.
13 It's also worth noting that TaskCluster workers ensure a cache can only
14 be used by 1 task at a time. If a worker is simultaneously running
15 multiple tasks requesting the same named cache, the worker will
16 have multiple caches of the same name on the worker.
18 Caches and ``run-task``
19 -----------------------
21 ``run-task`` is our generic task wrapper script. It does common activities
22 like ensure a version control checkout is present.
24 One of the roles of ``run-task`` is to verify and sanitize caches.
25 It does this by storing state in a cache on its first use. If the recorded
26 *capabilities* of an existing cache don't match expectations for the
27 current task, ``run-task`` bails. This ensures that caches are only
28 reused by tasks with similar execution *profiles*. This prevents
29 accidental cache use across incompatible tasks. It also allows run-task
30 to make assumptions about the state of caches, which can help avoid
33 In addition, the hash of ``run-task`` is used to derive the cache name.
34 So any time ``run-task`` changes, a new set of caches are used. This
35 ensures that any backwards incompatible changes or bug fixes to
36 ``run-task`` result in fresh caches.
38 Some caches are reserved for use with run-task. That property will be denoted
44 Version Control Caches
45 ::::::::::::::::::::::
47 ``level-{{level}}-checkouts-{{hash}}``
48 This cache holds version control checkouts, each in a subdirectory named
49 after the repo (e.g., ``gecko``).
51 Checkouts should be read-only. If a task needs to create new files from
52 content of a checkout, this content should be written in a separate
53 directory/cache (like a workspace).
55 This cache name pattern is managed by ``run-task`` and must only be
56 used with ``run-task``.
58 ``level-{{level}}-checkouts-sparse-{{hash}}``
59 This is like the above but is used when the checkout is sparse (contains
62 ``level-{{level}}-checkouts-{{version}}`` (deprecated)
63 This cache holds version control checkouts, each in a subdirectory named
64 after the repo (e.g., ``gecko``).
66 Checkouts should be read-only. If a task needs to create new files from
67 content of a checkout, this content should be written in a separate
68 directory/cache (like a workspace).
70 A ``version`` parameter appears in the cache name to allow
71 backwards-incompatible changes to the cache's behavior.
73 The ``hg-store`` contains a `shared store <https://www.mercurial-scm.org/wiki/ShareExtension>`
74 that is is used by ``hg robustcheckout``. If you are using ``run-task`` you
75 should set the ``HG_STORE_PATH`` environment variable to point to this
76 directory. If you are using ``hg robustcheckout``, pass this directory to the
77 ``--sharebase`` option.
82 ``level-{{level}}-*-workspace``
83 These caches (of various names typically ending with ``workspace``)
84 contain state to be shared between task invocations. Use cases are
85 dependent on the task.
90 ``level-{{level}}-tooltool-cache-{{hash}}``
91 Tooltool invocations should use this cache. Tooltool will store files here
92 indexed by their hash.
94 This cache name pattern is reserved for use with ``run-task`` and must only
95 be used by ``run-task``
97 ``tooltool-cache`` (deprecated)
98 Legacy location for tooltool files. Use the per-level one instead.