Add a base class for a global worker that locks via Redis

requirements-nover.txt

@@ -57,3 +57,4 @@ pyjwkest
 rfc3987
 jsonpath-rw
 bintrees
+redlock

requirements.txt

@@ -73,6 +73,7 @@ pytz==2015.4
 PyYAML==3.11
 raven==5.3.1
 redis==2.10.3
+redlock=1.1.0
 reportlab==2.7
 requests==2.7.0
 requests-oauthlib==0.5.0

workers/globalworkerbase.py

@@ -0,0 +1,33 @@
+import logging
+
+from workers.worker import Worker
+from redlock import RedLock, RedLockError
+
+logger = logging.getLogger(__name__)
+
+class GlobalWorker(Worker):
+  def __init__(self, app, sleep_period_seconds=3600, lock_ttl=600):
+    super(GlobalWorker, self).__init__()
+
+    worker_name = self.__class__.__name__
+
+    self._redis_info = app.config['USER_EVENTS_REDIS']
+    self._lock_name = '%s.global_lock' % (worker_name)
+    self._lock_ttl = lock_ttl
+
+    self.add_operation(self._prepare_global_work, sleep_period_seconds)
+
+  def _prepare_global_work(self):
+    try:
+      logger.debug('Acquiring lock %s', self._lock_name)
+      with RedLock(self._lock_name, connection_details=[self._redis_info],
+                   ttl=self._lock_ttl):
+        logger.debug('Acquired lock %s, performing work', self._lock_name)
+        self.perform_global_work()
+
+      logger.debug('Work complete, releasing lock %s', self._lock_name)
+    except RedLockError:
+      logger.debug('Could not acquire lock %s, going to sleep', self._lock_name)
+
+  def perform_global_work(self):
+    raise NotImplementedError('Workers must implement perform_global_work.')