Use Docker time limit for max lock age

When building a project, if it tooks more than `REPO_LOCK_SECONDS` and
while building after that time another build is triggered for the same
Version and the same builder takes the task the lock will be
considered "old" and remove and taken by the new build.

This will end up in a collision when accessing the files and it could
raise an exception like `IOError: [Errno 26] Text file busy`. Also, it
could fail with another unexpected reasons.

This PR increases the `max_lock_age` to the same value assigned for
the project to end the build in order:

* custom container time limit or,
* `settings.DOCKER_LIMITS['time']` or,
* `settings.REPO_LOCK_SECONDS` or,
* 30 seconds

Related to #1609

readthedocs/projects/models.py

@@ -651,8 +651,28 @@ def vcs_repo(self, version=LATEST, environment=None):
             repo = backend(self, version, environment)
         return repo
 
-    def repo_nonblockinglock(self, version, max_lock_age=5):
-        return NonBlockingLock(project=self, version=version, max_lock_age=max_lock_age)
+    def repo_nonblockinglock(self, version, max_lock_age=None):
+        """
+        Return a ``NonBlockingLock`` or raise an exception.
+
+        :param version: project's version that want to get the lock for.
+        :param max_lock_age: time (in seconds) to consider the lock's age is old
+            and grab it anyway. It default to the ``container_time_limit`` of
+            the project or the default ``DOCKER_LIMITS['time']`` or
+            ``REPO_LOCK_SECONDS`` or 30
+        """
+        if max_lock_age is None:
+            max_lock_age = (
+                self.container_time_limit or
+                getattr(settings, 'DOCKER_LIMITS', {}).get('time') or
+                getattr(settings, 'REPO_LOCK_SECONDS', 30)
+            )
+
+        return NonBlockingLock(
+            project=self,
+            version=version,
+            max_lock_age=max_lock_age,
+        )
 
     def repo_lock(self, version, timeout=5, polling_interval=5):
         return Lock(self, version, timeout, polling_interval)

readthedocs/projects/tasks.py

@@ -113,10 +113,7 @@ def sync_repo(self):
                 ),
             )
 
-        with self.project.repo_nonblockinglock(
-                version=self.version,
-                max_lock_age=getattr(settings, 'REPO_LOCK_SECONDS', 30)):
-
+        with self.project.repo_nonblockinglock(version=self.version):
             # Get the actual code on disk
             try:
                 before_vcs.send(sender=self.version)
@@ -649,10 +646,7 @@ def setup_python_environment(self):
         """
         self.build_env.update_build(state=BUILD_STATE_INSTALLING)
 
-        with self.project.repo_nonblockinglock(
-                version=self.version,
-                max_lock_age=getattr(settings, 'REPO_LOCK_SECONDS', 30)):
-
+        with self.project.repo_nonblockinglock(version=self.version):
             # Check if the python version/build image in the current venv is the
             # same to be used in this build and if it differs, wipe the venv to
             # avoid conflicts.
@@ -682,9 +676,7 @@ def build_docs(self):
         before_build.send(sender=self.version)
 
         outcomes = defaultdict(lambda: False)
-        with self.project.repo_nonblockinglock(
-                version=self.version,
-                max_lock_age=getattr(settings, 'REPO_LOCK_SECONDS', 30)):
+        with self.project.repo_nonblockinglock(version=self.version):
             outcomes['html'] = self.build_docs_html()
             outcomes['search'] = self.build_docs_search()
             outcomes['localmedia'] = self.build_docs_localmedia()