Use native Pub/Sub library primitives.

common/tsmon/monitor/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 monitor
 
 import (
         "net/http"
 
         "github.com/golang/protobuf/proto"
-        "github.com/luci/luci-go/common/gcloud/pubsub"
+        gcps "github.com/luci/luci-go/common/gcloud/pubsub"
         "github.com/luci/luci-go/common/tsmon/types"
         "golang.org/x/net/context"
+        "google.golang.org/cloud"
+        "google.golang.org/cloud/pubsub"
 )
 
-// ClientFactory is a function that creates an HTTP client.
-type ClientFactory func(ctx context.Context) (*http.Client, error)
-
 type pubSubMonitor struct {
-        clientFactory ClientFactory
-        topic         pubsub.Topic
+        topic *pubsub.TopicHandle
 }
 
 // NewPubsubMonitor returns a Monitor that sends metrics to the Cloud Pub/Sub
 // API.
 //
 // The provided client should do implement sufficient authentication to send
 // Cloud Pub/Sub requests.
-func NewPubsubMonitor(c ClientFactory, project string, topic string) (Monitor, error) {
+func NewPubsubMonitor(ctx context.Context, client *http.Client, topic gcps.Topic) (Monitor, error) {
+        project, name := topic.Split()
+
+        psClient, err := pubsub.NewClient(ctx, project, cloud.WithBaseHTTP(client))
+        if err != nil {
+                return nil, err
+        }
+
         return &pubSubMonitor{
-                clientFactory: c,
-                topic:         pubsub.NewTopic(project, topic),
+                topic: psClient.Topic(name),
         }, nil
 }
 
 func (m *pubSubMonitor) ChunkSize() int {
-        return 1000
+        return gcps.MaxPublishBatchSize
 }
 
 func (m *pubSubMonitor) Send(ctx context.Context, cells []types.Cell) error {
         collection := SerializeCells(cells)
 
         data, err := proto.Marshal(collection)
         if err != nil {
                 return err
         }
 
-        client, err := m.clientFactory(ctx)
-        if err != nil {
-                return err
-        }
-
-        ps := pubsub.NewConnection(client)
-        _, err = ps.Publish(ctx, m.topic, &pubsub.Message{Data: data})
+        _, err = m.topic.Publish(ctx, &pubsub.Message{Data: data})
         return err
 }