Bug 1618067 - rebuild-cached-tasks action r=taskgraph-reviewers,jmahe…

…r DONTBUILD

Cached tasks help us reuse existing tasks for toolchain, docker-image,
and fetch tasks, among others. This saves us compute cycles and
end-to-end time; it also allows us to keep these artifacts pinned
until we rebuild, which is a way to keep non-deterministic
artifacts, like docker images, in a predictable state.

However, occasionally we need to rebuild these tasks, e.g. when we
rotate the CoT key and want to invalidate the old key that we signed
the existing cached_tasks with. Until now, this process was unwieldy.
Now we have an action to allow us to do this at will.

Differential Revision: https://phabricator.services.mozilla.com/D118749

taskcluster/taskgraph/actions/rebuild_cached_tasks.py

@@ -0,0 +1,41 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import absolute_import, print_function, unicode_literals
+
+from .registry import register_callback_action
+from .util import (
+    create_tasks,
+    fetch_graph_and_labels,
+)
+
+
+@register_callback_action(
+    name="rebuild-cached-tasks",
+    title="Rebuild Cached Tasks",
+    symbol="rebuild-cached",
+    description="Rebuild cached tasks.",
+    order=1000,
+    context=[],
+)
+def rebuild_cached_tasks_action(
+    parameters, graph_config, input, task_group_id, task_id
+):
+    decision_task_id, full_task_graph, label_to_taskid = fetch_graph_and_labels(
+        parameters, graph_config
+    )
+    cached_tasks = [
+        label
+        for label, task in full_task_graph.tasks.items()
+        if task.attributes.get("cached_task", False)
+    ]
+    if cached_tasks:
+        create_tasks(
+            graph_config,
+            cached_tasks,
+            full_task_graph,
+            label_to_taskid,
+            parameters,
+            decision_task_id,
+        )