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subscribeWithFlowControlSettings.js
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// Copyright 2019-2020 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
//
// http://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 application demonstrates how to perform basic operations on
* subscriptions 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.
*/
'use strict';
// sample-metadata:
// title: Subscribe With Flow Control Settings
// description: Listen to messages with flow control settings, which are
// properties of the client/listener instance.
// usage: node subscribeWithFlowControlSettings.js <subscription-name>
// [max-in-progress [timeout-in-seconds]]
function main(
subscriptionName = 'YOUR_SUBSCRIPTION_NAME',
maxInProgress = 1,
timeout = 10
) {
maxInProgress = Number(maxInProgress);
timeout = Number(timeout);
// [START pubsub_subscriber_flow_settings]
/**
* TODO(developer): Uncomment these variables before running the sample.
*/
// const subscriptionName = 'YOUR_SUBSCRIPTION_NAME';
// const maxInProgress = 5;
// const timeout = 10;
// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');
// Creates a client; cache this for further use
const pubSubClient = new PubSub();
async function subscribeWithFlowControlSettings() {
const subscriberOptions = {
flowControl: {
maxMessages: maxInProgress,
},
};
// References an existing subscription.
// Note that flow control settings are not persistent across subscribers.
const subscription = pubSubClient.subscription(
subscriptionName,
subscriberOptions
);
console.log(
`Subscriber to subscription ${subscription.name} is ready to receive messages at a controlled volume of ${maxInProgress} messages.`
);
const messageHandler = message => {
console.log(`Received message: ${message.id}`);
console.log(`\tData: ${message.data}`);
console.log(`\tAttributes: ${message.attributes}`);
// "Ack" (acknowledge receipt of) the message
message.ack();
};
subscription.on('message', messageHandler);
setTimeout(() => {
subscription.close();
}, timeout * 1000);
}
// [END pubsub_subscriber_flow_settings]
subscribeWithFlowControlSettings().catch(console.error);
}
main(...process.argv.slice(2));