Use native Pub/Sub library primitives.

common/tsmon/monitor/pubsub.go

Index: common/tsmon/monitor/pubsub.go
diff --git a/common/tsmon/monitor/pubsub.go b/common/tsmon/monitor/pubsub.go
index 7fcd8cae832ffeae9fefe801c5efc7fcfd76249c..7299a48ca8a8d2105ca8c43276721ec3d34d1752 100644
--- a/common/tsmon/monitor/pubsub.go
+++ b/common/tsmon/monitor/pubsub.go
@@ -8,17 +8,15 @@ 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
@@ -26,15 +24,21 @@ type pubSubMonitor struct {
 //
 // 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 {
@@ -45,12 +49,6 @@ func (m *pubSubMonitor) Send(ctx context.Context, cells []types.Cell) error {
 		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
 }