LogDog: Add collector service implementation.

common/gcloud/gcps/pubsub.go

 // Copyright 2015 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.
 
 package gcps
 
 import (
+        "golang.org/x/net/context"
         "google.golang.org/cloud/pubsub"
 )
 
 var (
         // PublisherScopes is the set of OAuth2 scopes needed for a publisher to
         // publish messages.
         PublisherScopes = []string{
                 pubsub.ScopePubSub,
         }
 
         // SubscriberScopes is the set of OAuth2 scopes needed for a subscriber to
         // pull and acknowledge messages.
         SubscriberScopes = []string{
                 pubsub.ScopePubSub,
         }
 )
 
 // PubSub is an interface around Pub/Sub functionality.
 //
 // Any method may return an errors.TransientError to indicate that the
 // encountered error was transient.
 type PubSub interface {
         // TopicExists tests if a given Topic exists.
-        TopicExists(Topic) (bool, error)
+        TopicExists(context.Context, Topic) (bool, error)

[dnj (Google), 2016/01/21 04:36:24]

All methods take context.Context now. This is because we may want to cancel them
on a per-call basis (e.g., cancel the Pull, do not cancel the Ack). Previously
the only way to do this was two separate instances! This is more natural.

 
         // SubscriptionExists tests if a given Subscription exists.
-        SubExists(Subscription) (bool, error)
+        SubExists(context.Context, Subscription) (bool, error)
 
         // Publish publishes a batch of Pub/Sub messages.
-        Publish(Topic, ...*pubsub.Message) ([]string, error)
+        Publish(context.Context, Topic, ...*pubsub.Message) ([]string, error)
 
         // Pull pulls messages from the subscription. It returns up the requested
         // number of messages.
-        Pull(Subscription, int) ([]*pubsub.Message, error)
+        Pull(context.Context, Subscription, int) ([]*pubsub.Message, error)
 
         // Ack acknowledges one or more Pub/Sub message ACK IDs.
-        Ack(Subscription, ...string) error
+        Ack(context.Context, Subscription, ...string) error
 }