Fix bug where worker died from monitoring views.

Fixes #288.

Conflicts:
	rq/worker.py

rq/worker.py

@@ -326,9 +326,9 @@ class Worker(object):
                 self.log.info('%s: %s (%s)' % (green(queue.name),
                     blue(job.description), job.id))
 
-                self.connection.expire(self.key, (job.timeout or 180) + 60)
+                self.heartbeat((job.timeout or Queue.DEFAULT_TIMEOUT) + 60)
                 self.fork_and_perform_job(job)
-                self.connection.expire(self.key, self.default_worker_ttl)
+                self.heartbeat()
 
                 did_perform_work = True
         finally:
@@ -338,16 +338,34 @@ class Worker(object):
 
 
     def dequeue_job_and_maintain_ttl(self, timeout):
+        result = None
         while True:
+            self.heartbeat()
             try:
-                return Queue.dequeue_any(self.queues, timeout,
-                        connection=self.connection)
+                result = Queue.dequeue_any(self.queues, timeout,
+                                           connection=self.connection)
+                break
             except DequeueTimeout:
                 pass
 
-            self.log.debug('Sending heartbeat to prevent worker timeout.')
-            self.connection.expire(self.key, self.default_worker_ttl)
+        self.heartbeat()
+        return result
+
+    def heartbeat(self, timeout=0):
+        """Specifies a new worker timeout, typically by extending the
+        expiration time of the worker, effectively making this a "heartbeat"
+        to not expire the worker until the timeout passes.
 
+        The next heartbeat should come before this time, or the worker will
+        die (at least from the monitoring dashboards).
+
+        The effective timeout can never be shorter than default_worker_ttl,
+        only larger.
+        """
+        timeout = max(timeout, self.default_worker_ttl)
+        self.connection.expire(self.key, timeout)
+        self.log.debug('Sent heartbeat to prevent worker timeout. '
+                       'Next one should arrive within {} seconds.'.format(timeout))
 
     def fork_and_perform_job(self, job):
         """Spawns a work horse to perform the actual work and passes it a job.