Use a datastore batcher for build queries.

milo/appengine/buildbot/pubsub.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package buildbot
 
 import (
         "bytes"
         "compress/gzip"
         "compress/zlib"
@@ skipping 220 matching lines @@
                 return 500
         }
         masterCounter.Add(c, 1, internal, fullname, "success")
 
         // Extract current builds data out of the master json, and use it to
         // clean up expired builds.
         q := ds.NewQuery("buildbotBuild").
                 Eq("finished", false).
                 Eq("master", master.Name)
         builds := []*buildbotBuild{}
-        err = ds.GetAll(c, q, &builds)
+        err = getBuildQueryBatcher(c).GetAll(c, q, &builds)
         if err != nil {
                 logging.WithError(err).Errorf(c, "Could not load current builds from master %s",
                         master.Name)
                 return 500
         }
         for _, b := range builds {
                 builder, ok := master.Builders[b.Buildername]
                 if !ok {
                         // Mark this build due to builder being removed.
                         buildCounter.Add(
@@ skipping 145 matching lines @@
 
         }
         if master != nil {
                 code := doMaster(c, master, internal)
                 if code != 0 {
                         return code
                 }
         }
         return 200
 }