Milo: Use custom config caching layer

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 286 matching lines @@
         now := int(clock.Now(c).Unix())
         defer r.Body.Close()
         dec := json.NewDecoder(r.Body)
         if err := dec.Decode(&msg); err != nil {
                 logging.WithError(err).Errorf(
                         c, "Could not decode message.  %s", err)
                 return http.StatusOK // This is a hard failure, we don't want PubSub to retry.
         }
         internal := true
         // Get the name of the subscription on luci-config
-        settings, err := common.GetSettings(c)
-        if err != nil {
-                logging.WithError(err).Errorf(c,
-                        "Cannot load settings to check subscription name.")
-                // This is a configuration error. Tell PubSub to retry until we fix our
-                // configs.
-                return http.StatusInternalServerError
-        }
+        settings := common.GetSettings(c)
         switch msg.Subscription {
         case settings.Buildbot.PublicSubscription:
                 internal = false
         case settings.Buildbot.InternalSubscription:
                 // internal = true, but that's already set.
         default:
                 logging.Errorf(
                         c, "Subscription name %s does not match %s or %s",
                         msg.Subscription, settings.Buildbot.PublicSubscription,
                         settings.Buildbot.InternalSubscription)
@@ skipping 80 matching lines @@
 
         }
         if master != nil {
                 code := doMaster(c, master, internal)
                 if code != 0 {
                         return code
                 }
         }
         return http.StatusOK
 }