Build: move cancel_build to readthedocs.core.utils.__init__

Wrap the code that cancels a build and move it the module where `trigger_build`
and other related helpers are.

Author: humitos

readthedocs/builds/views.py

@@ -1,6 +1,5 @@
 """Views for builds app."""
 
-import signal
 import textwrap
 from urllib.parse import urlparse
 
@@ -23,10 +22,9 @@
 from readthedocs.builds.filters import BuildListFilter
 from readthedocs.builds.models import Build, Version
 from readthedocs.core.permissions import AdminPermission
-from readthedocs.core.utils import trigger_build
-from readthedocs.doc_builder.exceptions import BuildAppError, BuildCancelled
+from readthedocs.core.utils import cancel_build, trigger_build
+from readthedocs.doc_builder.exceptions import BuildAppError
 from readthedocs.projects.models import Project
-from readthedocs.worker import app
 
 log = structlog.get_logger(__name__)
 
@@ -167,33 +165,7 @@ def post(self, request, project_slug, build_pk):
         if not AdminPermission.is_admin(request.user, project):
             return HttpResponseForbidden()
 
-        # NOTE: `terminate=True` is required for the child to attend our call
-        # immediately when it's running the build. Otherwise, it finishes the
-        # task. However, to revoke a task that has not started yet, we don't
-        # need it.
-        if build.state == BUILD_STATE_TRIGGERED:
-            # Since the task won't be executed at all, we need to update the
-            # Build object here.
-            terminate = False
-            build.state = BUILD_STATE_CANCELLED
-            build.success = False
-            build.error = BuildCancelled.message
-            build.length = 0
-            build.save()
-        else:
-            # In this case, we left the update of the Build object to the task
-            # itself to be executed in the `on_failure` handler.
-            terminate = True
-
-        log.warning(
-            'Canceling build.',
-            project_slug=project.slug,
-            version_slug=build.version.slug,
-            build_id=build.pk,
-            build_task_id=build.task_id,
-            terminate=terminate,
-        )
-        app.control.revoke(build.task_id, signal=signal.SIGINT, terminate=terminate)
+        cancel_build(build)
 
         return HttpResponseRedirect(
             reverse('builds_detail', args=[project.slug, build.pk]),

readthedocs/core/utils/__init__.py

@@ -2,6 +2,7 @@
 
 import datetime
 import re
+import signal
 
 import structlog
 from django.conf import settings
@@ -19,9 +20,11 @@
     EXTERNAL,
 )
 from readthedocs.doc_builder.exceptions import (
+    BuildCancelled,
     BuildMaxConcurrencyError,
     DuplicatedBuildError,
 )
+from readthedocs.worker import app
 
 log = structlog.get_logger(__name__)
 
@@ -249,6 +252,48 @@ def trigger_build(project, version=None, commit=None):
     return task, build
 
 
+def cancel_build(build):
+    """
+    Cancel a triggered/running build.
+
+    Depending on the current state of the build, it takes one approach or the other:
+
+    - Triggered:
+        update the build status and tells Celery to revoke this task.
+        Workers will know about this and will discard it.
+    - Running:
+        communicate Celery to force the termination of the current build
+        and relies on the worker to update the build's status correct.
+    """
+    # NOTE: `terminate=True` is required for the child to attend our call
+    # immediately when it's running the build. Otherwise, it finishes the
+    # task. However, to revoke a task that has not started yet, we don't
+    # need it.
+    if build.state == BUILD_STATE_TRIGGERED:
+        # Since the task won't be executed at all, we need to update the
+        # Build object here.
+        terminate = False
+        build.state = BUILD_STATE_CANCELLED
+        build.success = False
+        build.error = BuildCancelled.message
+        build.length = 0
+        build.save()
+    else:
+        # In this case, we left the update of the Build object to the task
+        # itself to be executed in the `on_failure` handler.
+        terminate = True
+
+    log.warning(
+        "Canceling build.",
+        project_slug=build.project.slug,
+        version_slug=build.version.slug,
+        build_id=build.pk,
+        build_task_id=build.task_id,
+        terminate=terminate,
+    )
+    app.control.revoke(build.task_id, signal=signal.SIGINT, terminate=terminate)
+
+
 def send_email(
         recipient, subject, template, template_html, context=None, request=None,
         from_email=None, **kwargs