Make the loop pause when we run out of builder capacity.

buildman/server.py

@@ -139,15 +139,16 @@ class BuilderServer(object):
   @trollius.coroutine
   def _work_checker(self):
     while self._current_status == 'running':
+      with database.CloseForLongOperation(app.config):
+        yield From(trollius.sleep(WORK_CHECK_TIMEOUT))
+
       logger.debug('Checking for more work for %d active workers',
                    self._lifecycle_manager.num_workers())
 
       job_item = self._queue.get(processing_time=self._lifecycle_manager.setup_time())
       if job_item is None:
         logger.debug('No additional work found. Going to sleep for %s seconds', WORK_CHECK_TIMEOUT)
-        with database.CloseForLongOperation(app.config):
-          yield From(trollius.sleep(WORK_CHECK_TIMEOUT))
-          continue
+        continue
 
       try:
         build_job = BuildJob(job_item)
@@ -164,6 +165,8 @@ class BuilderServer(object):
         logger.debug('All workers are busy. Requeuing.')
         self._queue.incomplete(job_item, restore_retry=True, retry_after=0)
 
+
+
   @trollius.coroutine
   def _initialize(self, loop, host, websocket_port, controller_port, ssl=None):
     self._loop = loop