Add more logging to builder_alerts

infra/services/builder_alerts/alert_builder.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 import argparse
 import json
 import logging
 import multiprocessing
 import os
 import re
 import sys
@@ skipping 330 matching lines @@
 
 
 def alerts_for_master(cache, master_url, master_json, old_alerts,
                       builder_name_filter=None, jobs=1):  # pragma: no cover
   active_builds = []
   for slave in master_json['slaves'].values():
     for build in slave['runningBuilds']:
       active_builds.append(build)
 
   def process_builder(builder_name):
+    logging.debug('Thread for builder %s has started', builder_name)
     try:
       if builder_name_filter and builder_name_filter not in builder_name:
         return None
 
       builder_json = master_json['builders'][builder_name]
 
       # cachedBuilds will include runningBuilds.
       recent_build_ids = builder_json['cachedBuilds']
 
       if not recent_build_ids:
         return None
 
       buildbot.warm_build_cache(cache, master_url, builder_name,
                                 recent_build_ids, active_builds)
       return alerts_for_builder(cache, master_url, builder_name,
                                 recent_build_ids, old_alerts)
     except:
       # Put all exception text into an exception and raise that so it doesn't
       # get eaten by the multiprocessing code.
       raise Exception(''.join(traceback.format_exception(*sys.exc_info())))
+    finally:
+      logging.debug('Thread for builder %s has finished', builder_name)
 
   pool = multiprocessing.dummy.Pool(processes=jobs)
+  logging.debug('Processing all threads via thread pool')
   builder_alerts = pool.map(process_builder, master_json['builders'].keys())
+  logging.debug('Closing all threads in thread pool')
   pool.close()
   pool.join()
+  logging.debug('Joined all threads in thread pool')
 
   alerts = []
   for alert in builder_alerts:
     if alert:
       alerts.extend(alert)
 
   stale_master_data_alert = alert_for_stale_master_data(master_url, master_json)
   return (alerts, stale_master_data_alert)
 
 
@@ skipping 15 matching lines @@
   master_url = match.group('master_url')
   builder_name = urllib.unquote_plus(match.group('builder_name'))
   master_json = buildbot.fetch_master_json(master_url)
   # This is kinda a hack, but uses more of our existing code this way:
   alerts = alerts_for_master(cache, master_url, master_json, builder_name)
   print json.dumps(alerts[0], indent=1)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))