publishOrderedMessage.js

// Copyright 2019-2024 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.

// This is a generated sample, using the typeless sample bot. Please
// look for the source TypeScript sample (.ts) for modifications.
'use strict';

/**
 * This sample demonstrates how to perform basic operations on topics with
 * the Google Cloud Pub/Sub API.
 *
 * For more information, see the README.md under /pubsub and the documentation
 * at https://cloud.google.com/pubsub/docs.
 */

// sample-metadata:
//   title: Publish Ordered Message
//   description: Demonstrates how to publish messages to a topic
//     with ordering. Please see "Create Subscription With Ordering" for
//     information on setting up a subscription that will receive the
//     messages with proper ordering.
//   usage: node publishOrderedMessage.js <topic-name-or-id> <data>

// [START pubsub_publish_with_ordering_keys]
/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const data = JSON.stringify({foo: 'bar'});
// const orderingKey = 'key1';

// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');

// Creates a client; cache this for further use
const pubSubClient = new PubSub({
  // Sending messages to the same region ensures they are received in order
  // even when multiple publishers are used.
  apiEndpoint: 'us-east1-pubsub.googleapis.com:443',
});

async function publishOrderedMessage(topicNameOrId, data, orderingKey) {
  // Publishes the message as a string, e.g. "Hello, world!" or JSON.stringify(someObject)
  const dataBuffer = Buffer.from(data);

  // Be sure to set an ordering key that matches other messages
  // you want to receive in order, relative to each other.
  const message = {
    data: dataBuffer,
    orderingKey: orderingKey,
  };

  // Cache topic objects (publishers) and reuse them.
  //
  // Pub/Sub's ordered delivery guarantee only applies when publishes for an ordering
  // key are in the same region. For list of locational endpoints for Pub/Sub, see:
  // https://cloud.google.com/pubsub/docs/reference/service_apis_overview#list_of_locational_endpoints
  const publishOptions = {
    messageOrdering: true,
  };
  const topic = pubSubClient.topic(topicNameOrId, publishOptions);

  // Publishes the message
  const messageId = topic.publishMessage(message);

  console.log(`Message ${messageId} published.`);

  return messageId;
}
// [END pubsub_publish_with_ordering_keys]

async function main(
  topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID',
  data = JSON.stringify({foo: 'bar'}),
  orderingKey = 'key1'
) {
  await publishOrderedMessage(topicNameOrId, data, orderingKey).catch(err => {
    console.error(err.message);
    process.exitCode = 1;
  });
}

main(...process.argv.slice(2));