Oops - set the master field to an empty string.

scripts/master/monitoring_status_receiver.py

 # Copyright 2016 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 collections
 import time
 
 from buildbot.status.base import StatusReceiverMultiService
 from twisted.internet import defer, reactor, task
 from twisted.python import log, threadpool
@@ skipping 51 matching lines @@
 
   @defer.inlineCallbacks
   def updateMetricsAndFlush(self):
     try:
       yield self.updateMetrics()
     finally:
       self.thread_pool.callInThread(self._flush_and_log_exceptions)
 
   @defer.inlineCallbacks
   def updateMetrics(self):
-    uptime.set(time.time() - SERVER_STARTED)
-    accepting_builds.set(bool(self.status.master.botmaster.brd.running))
+    uptime.set(time.time() - SERVER_STARTED, fields={'master': ''})
+    accepting_builds.set(bool(self.status.master.botmaster.brd.running),
+                         fields={'master': ''})
     pool = self.status.master.db.pool
-    pool_queue.set(pool.q.qsize())
-    pool_waiting.set(len(pool.waiters))
-    pool_working.set(len(pool.working))
+    pool_queue.set(pool.q.qsize(), fields={'master': ''})
+    pool_waiting.set(len(pool.waiters), fields={'master': ''})
+    pool_working.set(len(pool.working), fields={'master': ''})
 
     for builder_name in self.status.getBuilderNames():
-      fields = {'builder': builder_name}
+      fields = {'builder': builder_name, 'master': ''}
       builder = self.status.getBuilder(builder_name)
       slaves = builder.getSlaves()
 
       connected.set(sum(1 for x in slaves if x.connected), fields=fields)
       current_builds.set(len(builder.getCurrentBuilds()), fields=fields)
       state.set(builder.currentBigState, fields=fields)
       total.set(len(slaves), fields=fields)
 
     # Get pending build requests directly from the db for all builders at
     # once.
     d = self.status.master.db.buildrequests.getBuildRequests(claimed=False)
 
     # Timeout the database request after 5 seconds.
     def timeout():
       if not d.called:
         d.cancel()
     reactor.callLater(5, timeout)
 
     try:
       brdicts = yield d
     except Exception as ex:
       log.err(ex, 'getBuildRequests failed while failed populating metrics')
     else:
       pending_per_builder = collections.defaultdict(int)
       for brdict in brdicts:
         pending_per_builder[brdict['buildername']] += 1
 
       for builder_name, count in pending_per_builder.iteritems():
-        pending_builds.set(count, fields={'builder': builder_name})
+        pending_builds.set(count,
+                           fields={'builder': builder_name, 'master': ''})
 
   def _flush_and_log_exceptions(self):
     try:
       ts_mon.flush()
     except Exception:
       log.err(None, 'Automatic monitoring flush failed.')