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- // Copyright 2018 Google LLC
- //
- // Licensed under the Apache License, Version 2.0 (the "License");
- // you may not use this file except in compliance with the License.
- // You may obtain a copy of the License at
- //
- // https://www.apache.org/licenses/LICENSE-2.0
- //
- // Unless required by applicable law or agreed to in writing, software
- // distributed under the License is distributed on an "AS IS" BASIS,
- // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- // See the License for the specific language governing permissions and
- // limitations under the License.
-
- package pubsub_test
-
- import (
- "fmt"
- "log"
- "time"
-
- "cloud.google.com/go/pubsub/apiv1"
- "golang.org/x/net/context"
- pubsubpb "google.golang.org/genproto/googleapis/pubsub/v1"
- )
-
- func ExampleSubscriberClient_Pull_lengthyClientProcessing() {
- projectID := "some-project"
- subscriptionID := "some-subscription"
-
- ctx := context.Background()
- client, err := pubsub.NewSubscriberClient(ctx)
- if err != nil {
- log.Fatal(err)
- }
- defer client.Close()
-
- sub := fmt.Sprintf("projects/%s/subscriptions/%s", projectID, subscriptionID)
- // Be sure to tune the MaxMessages parameter per your project's needs, and accordingly
- // adjust the ack behavior below to batch acknowledgements.
- req := pubsubpb.PullRequest{
- Subscription: sub,
- MaxMessages: 1,
- }
-
- fmt.Println("Listening..")
-
- for {
- res, err := client.Pull(ctx, &req)
- if err != nil {
- log.Fatal(err)
- }
-
- // client.Pull returns an empty list if there are no messages available in the
- // backlog. We should skip processing steps when that happens.
- if len(res.ReceivedMessages) == 0 {
- continue
- }
-
- var recvdAckIDs []string
- for _, m := range res.ReceivedMessages {
- recvdAckIDs = append(recvdAckIDs, m.AckId)
- }
-
- var done = make(chan struct{})
- var delay = 0 * time.Second // Tick immediately upon reception
- var ackDeadline = 10 * time.Second
-
- // Continuously notify the server that processing is still happening on this batch.
- go func() {
- for {
- select {
- case <-ctx.Done():
- return
- case <-done:
- return
- case <-time.After(delay):
- err := client.ModifyAckDeadline(ctx, &pubsubpb.ModifyAckDeadlineRequest{
- Subscription: sub,
- AckIds: recvdAckIDs,
- AckDeadlineSeconds: int32(ackDeadline.Seconds()),
- })
- if err != nil {
- log.Fatal(err)
- }
- delay = ackDeadline - 5*time.Second // 5 seconds grace period.
- }
- }
- }()
-
- for _, m := range res.ReceivedMessages {
- // Process the message here, possibly in a goroutine.
- log.Printf("Got message: %s", string(m.Message.Data))
-
- err := client.Acknowledge(ctx, &pubsubpb.AcknowledgeRequest{
- Subscription: sub,
- AckIds: []string{m.AckId},
- })
- if err != nil {
- log.Fatal(err)
- }
- }
-
- close(done)
- }
- }
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