/
publish_flow_control.go
79 lines (69 loc) · 2.27 KB
/
publish_flow_control.go
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// Copyright 2019 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 topics
// [START pubsub_publisher_flow_control]
import (
"context"
"fmt"
"io"
"strconv"
"sync"
"sync/atomic"
"cloud.google.com/go/pubsub"
)
func publishWithFlowControlSettings(w io.Writer, projectID, topicID string) error {
// projectID := "my-project-id"
// topicID := "my-topic"
ctx := context.Background()
client, err := pubsub.NewClient(ctx, projectID)
if err != nil {
return fmt.Errorf("pubsub.NewClient: %w", err)
}
defer client.Close()
t := client.Topic(topicID)
t.PublishSettings.FlowControlSettings = pubsub.FlowControlSettings{
MaxOutstandingMessages: 100, // default 1000
MaxOutstandingBytes: 10 * 1024 * 1024, // default 0 (unlimited)
LimitExceededBehavior: pubsub.FlowControlBlock, // default Ignore, other options: Block and SignalError
}
var wg sync.WaitGroup
var totalErrors uint64
numMsgs := 1000
// Rapidly publishing 1000 messages in a loop may be constrained by flow control.
for i := 0; i < numMsgs; i++ {
wg.Add(1)
result := t.Publish(ctx, &pubsub.Message{
Data: []byte("message #" + strconv.Itoa(i)),
})
go func(i int, res *pubsub.PublishResult) {
fmt.Fprintf(w, "Publishing message %d\n", i)
defer wg.Done()
// The Get method blocks until a server-generated ID or
// an error is returned for the published message.
_, err := res.Get(ctx)
if err != nil {
// Error handling code can be added here.
fmt.Fprintf(w, "Failed to publish: %v", err)
atomic.AddUint64(&totalErrors, 1)
return
}
}(i, result)
}
wg.Wait()
if totalErrors > 0 {
return fmt.Errorf("%d of %d messages did not publish successfully", totalErrors, numMsgs)
}
return nil
}
// [END pubsub_publisher_flow_control]