import (
"context"
"fmt"
"io"
"cloud.google.com/go/pubsub"
"cloud.google.com/go/pubsublite/pscompat"
)
func publishWithOrderingKey(w io.Writer, projectID, zone, topicID string, messageCount int) error {
// projectID := "my-project-id"
// zone := "us-central1-a"
// topicID := "my-topic"
// messageCount := 10
ctx := context.Background()
topicPath := fmt.Sprintf("projects/%s/locations/%s/topics/%s", projectID, zone, topicID)
// Create the publisher client.
publisher, err := pscompat.NewPublisherClient(ctx, topicPath)
if err != nil {
return fmt.Errorf("pscompat.NewPublisherClient error: %w", err)
}
// Ensure the publisher will be shut down.
defer publisher.Stop()
// Messages of the same ordering key will always get published to the same
// partition. When OrderingKey is unset, messages can get published to
// different partitions if more than one partition exists for the topic.
var results []*pubsub.PublishResult
for i := 0; i < messageCount; i++ {
r := publisher.Publish(ctx, &pubsub.Message{
OrderingKey: "test_ordering_key",
Data: []byte(fmt.Sprintf("message-%d", i)),
})
results = append(results, r)
}
// Print publish results.
var publishedCount int
for _, r := range results {
// Get blocks until the result is ready.
id, err := r.Get(ctx)
if err != nil {
// NOTE: A failed PublishResult indicates that the publisher client
// encountered a fatal error and has permanently terminated. After the
// fatal error has been resolved, a new publisher client instance must be
// created to republish failed messages.
fmt.Fprintf(w, "Publish error: %v\n", err)
continue
}
// Metadata decoded from the id contains the partition and offset.
metadata, err := pscompat.ParseMessageMetadata(id)
if err != nil {
return fmt.Errorf("failed to parse message metadata %q: %w", id, err)
}
fmt.Fprintf(w, "Published: partition=%d, offset=%d\n", metadata.Partition, metadata.Offset)
publishedCount++
}
fmt.Fprintf(w, "Published %d messages with ordering key\n", publishedCount)
return publisher.Error()
}
