Build: ability to cancel a running build from dashboard

We tried to implement this in another opportunities (see
#7031) but the build process
was really complex and we had to manage the exception in multiple places.

After implementing Celery Handlers, we can just raise the exception when
attending to the proper signal coming from `app.control.revoke` and handle it
properly from `on_failure` task's method.

All the initial local tests were great!

readthedocs/builds/migrations/0038_track_task_id.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.11 on 2022-01-26 20:10
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('builds', '0037_alter_build_cold_storage'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='build',
+            name='task_id',
+            field=models.CharField(blank=True, max_length=36, null=True, verbose_name='Celery task id'),
+        ),
+    ]

readthedocs/builds/models.py

@@ -5,7 +5,6 @@
 import os.path
 import re
 from functools import partial
-from shutil import rmtree
 
 import regex
 from django.conf import settings
@@ -667,6 +666,13 @@ class Build(models.Model):
         help_text='Build steps stored outside the database.',
     )
 
+    task_id = models.CharField(
+        _('Celery task id'),
+        max_length=36,
+        null=True,
+        blank=True,
+    )
+
     # Managers
     objects = BuildQuerySet.as_manager()
     # Only include BRANCH, TAG, UNKNOWN type Version builds.

readthedocs/builds/views.py

@@ -1,5 +1,7 @@
 """Views for builds app."""
 
+import signal
+
 import structlog
 import textwrap
 from urllib.parse import urlparse
@@ -21,6 +23,12 @@
 from readthedocs.doc_builder.exceptions import BuildAppError
 from readthedocs.projects.models import Project
 
+try:
+    from readthedocsinc.worker import app
+except ImportError:
+    from readthedocs.worker import app
+
+
 log = structlog.get_logger(__name__)
 
 
@@ -148,6 +156,22 @@ class BuildDetail(BuildBase, DetailView):
 
     pk_url_kwarg = 'build_pk'
 
+    @method_decorator(login_required)
+    def post(self, request, project_slug, build_pk):
+        project = get_object_or_404(Project, slug=project_slug)
+        build = get_object_or_404(Build, pk=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. Otherwise, it finishes the task.
+        app.control.revoke(build.task_id, signal=signal.SIGINT, terminate=True)
+
+        return HttpResponseRedirect(
+            reverse('builds_detail', args=[project.slug, build.pk]),
+        )
+
     def get_context_data(self, **kwargs):
         context = super().get_context_data(**kwargs)
         context['project'] = self.project

readthedocs/core/utils/__init__.py

@@ -239,7 +239,13 @@ def trigger_build(project, version=None, commit=None):
         # Build was skipped
         return (None, None)
 
-    return (update_docs_task.apply_async(), build)
+    task = update_docs_task.apply_async()
+
+    # Store the task_id in the build object to be able to cancel it later.
+    build.task_id = task.id
+    build.save()
+
+    return task, build
 
 
 def send_email(

readthedocs/doc_builder/exceptions.py

@@ -59,6 +59,10 @@ class DuplicatedBuildError(BuildUserError):
     status = BUILD_STATUS_DUPLICATED
 
 
+class BuildCancelled(BuildUserError):
+    message = gettext_noop('Build cancelled by user.')
+
+
 class MkDocsYAMLParseError(BuildUserError):
     GENERIC_WITH_PARSE_EXCEPTION = gettext_noop(
         'Problem parsing MkDocs YAML configuration. {exception}',

readthedocs/projects/tasks/builds.py

@@ -51,6 +51,7 @@
     BuildUserError,
     BuildMaxConcurrencyError,
     DuplicatedBuildError,
+    BuildCancelled,
     ProjectBuildsSkippedError,
     YAMLParseError,
 )
@@ -206,6 +207,7 @@ class UpdateDocsTask(SyncRepositoryMixin, Task):
         ProjectBuildsSkippedError,
         ConfigError,
         YAMLParseError,
+        BuildCancelled,
     )
 
     acks_late = True
@@ -221,10 +223,17 @@ def _setup_sigterm(self):
         def sigterm_received(*args, **kwargs):
             log.warning('SIGTERM received. Waiting for build to stop gracefully after it finishes.')
 
+        def sigint_received(*args, **kwargs):
+            log.warning('SIGINT received. Cancelling the build running.')
+            raise BuildCancelled
+
         # Do not send the SIGTERM signal to children (pip is automatically killed when
         # receives SIGTERM and make the build to fail one command and stop build)
         signal.signal(signal.SIGTERM, sigterm_received)
 
+
+        signal.signal(signal.SIGINT, sigint_received)
+
     def _check_concurrency_limit(self):
         try:
             response = api_v2.build.concurrent.get(project__slug=self.project.slug)

readthedocs/templates/builds/build_detail.html

@@ -30,6 +30,11 @@
 {% block content %}
   <div class="build build-detail" id="build-detail">
 
+    <form method="post" action="{% url "builds_detail" build.version.project.slug build.pk %}">
+      {% csrf_token %}
+      <input type="submit" value="{% trans "Cancel build" %}">
+    </form>
+
     <!-- Build meta data -->
     <ul class="build-meta">
       <div data-bind="visible: finished()">