Execute merge jobs via ZooKeeper

This is the second part of I767c0b4c5473b2948487c3ae5bbc612c25a2a24a.
It uses the MergerAPI.

Note: since we no longer have a central gearman server where we can
record all of the merge jobs, some tests now consult the merger api
to get the list of merge jobs which were submitted by that scheduler.
This should generally be equivalent, but something to keep in mind
as we add multiple schedulers.

Change-Id: I1c694bcdc967283f1b1a4821df7700d93240690a

zuul/executor/server.py

@@ -44,8 +44,6 @@ from zuul.lib import filecomments
 from zuul.lib.keystorage import ZooKeeperKeyStorage
 from zuul.lib.varnames import check_varnames
 
-import gear
-
 import zuul.lib.repl
 import zuul.merger.merger
 import zuul.ansible.logconfig
@@ -3016,19 +3014,6 @@ class AnsibleJob(object):
         return result, code
 
 
-class ExecutorMergeWorker(gear.TextWorker):
-    def __init__(self, executor_server, *args, **kw):
-        self.zuul_executor_server = executor_server
-        super(ExecutorMergeWorker, self).__init__(*args, **kw)
-
-    def handleNoop(self, packet):
-        # Wait until the update queue is empty before responding
-        while self.zuul_executor_server.update_queue.qsize():
-            time.sleep(1)
-
-        super(ExecutorMergeWorker, self).handleNoop(packet)
-
-
 class ExecutorServer(BaseMergeServer):
     log = logging.getLogger("zuul.ExecutorServer")
     _ansible_manager_class = AnsibleManager
@@ -3242,10 +3227,6 @@ class ExecutorServer(BaseMergeServer):
     def accepting_work(self, work):
         self.component_info.accepting_work = work
 
-    def noop(self, job):
-        """A noop gearman job so we can register for statistics."""
-        job.sendWorkComplete()
-
     def start(self):
         # Start merger worker only if we process merge jobs
         if self.process_merge_jobs:
@@ -3305,9 +3286,6 @@ class ExecutorServer(BaseMergeServer):
         # it has stopped.
         self.governor_stop_event.set()
         self.governor_thread.join()
-        # Stop accepting new jobs
-        if self.merger_gearworker is not None:
-            self.merger_gearworker.gearman.setFunctions([])
         # Tell the executor worker to abort any jobs it just accepted,
         # and grab the list of currently running job workers.
         with self.run_lock:
@@ -3337,7 +3315,7 @@ class ExecutorServer(BaseMergeServer):
         self.command_socket.stop()
 
         # All job results should have been sent by now, shutdown the
-        # gearman workers.
+        # build and merger workers.
         self.build_loop_wake_event.set()
         self.build_worker.join()