Can you publish multiple messages to an SNS topic using an AWS Lambda function backed by node.js 8.10?

Question

There is a related question regarding how to publish s single message: Can you publish a message to an SNS topic using an AWS Lambda function backed by node.js?

However, my question is related to publish more than one message. I am using node 8.10 and my handler is asynchronous.

yes, I works without async+await and when I make the handler async it fails — Alex Schwartz, Jun 01 '18 at 14:05

score 1 · Answer 1 · answered Mar 19 '19 at 08:50

You can use the Promise.all() feature to encapsulate multiple calls to sns.publish.

Create a one-notification-publish function that returns Promise:

.

function onePublishPromise(notificationParams){ 
  return new Promise((resolve, reject) => {
    sns.publish(notificationParams, function(err, data) {
        if (err) {
            console.error("Unable to send notification message. Error JSON:", JSON.stringify(err, null, 2));
            reject(err);
        } else {
            console.log("Results from sending notification message: ", JSON.stringify(data, null, 2));
            resolve(null);
        }
    });
  });
}

Create and send notifications in parallel:

// Create notifications params const notifications = [ {

    Subject: 'A new notification',
    Message: 'Some message',
    TopicArn: 'arn:aws:sns:us-west-1:000000000:SomeTopic'

   }
   // , ...
];
// Send all notifications
const notificationsDelivery = notifications.map(onePublishPromise);
// Wait for delivery results
Promise.all(notificationsDelivery).then(callback).catch(callback);

callback will be called after all messages published (successfully or not)

score 0 · Answer 2 · answered Jun 01 '18 at 14:17

The related question uses context.done, which would end the lambda before making a second call. Using

sns.publish(params, function(err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else     console.log(data);           // successful response
});

you can make more calls, e.g.

sns.publish(params2, function(err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else     console.log(data);           // successful response
});

Whether you want to use async.waterfall, nest the calls or let them go asynchronously is up to you.

Can you publish multiple messages to an SNS topic using an AWS Lambda function backed by node.js 8.10?

2 Answers2