Publishing SNS message from lambda (node js) result in timeout error

Question

I have used a very simple code slightly modified from AWS provided example:

    exports.handler = async (event) => {
        // Load the AWS SDK for Node.js
        var AWS = require('aws-sdk');
        // Set region
        AWS.config.update({region: 'ap-southeast-2'});
    
        // Create publish parameters
        var params = {
            Message: 'This is a sample message',
            Subject: 'Test SNS From Lambda',
            TopicArn: 'arn:aws:sns:ap-southeast-2:577913011449:TestTopic'
        };
    
        // Create promise and SNS service object
        var publishTextPromise = new AWS.SNS().publish(params).promise();
    
        let response = {
            statusCode: 200,
            body: JSON.stringify('Hello from Lambda!'),
        };
    
        // Handle promise's fulfilled/rejected states
        publishTextPromise.then(
            function(data) {
                console.log("Message ${params.Message} send sent to the topic ${params.TopicArn}");
                console.log("MessageID is " + data.MessageId);
                response.result = 'Success';
            }).catch(
                function(err) {
                console.error(err, err.stack);
                response.result = 'Error';
            });
    
        
        return response;
    };

And I am getting a timeout error when testing this service. 3 seconds is the limit.

Since this is a very simply process, I suppose it shouldn't take more than 3 seconds to execute.

I have checked my IAM setting and grant my profile (admin profile) to have full access to SNS service. But the error still persists. I am wondering what is being wrong here and how should I fix this?

Answer 1

I am not sure why you're getting the timeout, but your code isn't supposed to work the way you might expect.

See that you're returning your response outside your .then() code, meaning that your code is going to return before your .then() code is even run (Promises are asynchronous).

Since you're already using Node 8, you're better off using async/await instead of using the old .then().catch() approach.

I have refactored your code a little bit and it works just fine. I have kept the original parameters for your convenience. See how the code is much easier to read and debug.

    'use strict';
    
    // Load the AWS SDK for Node.js
    const AWS = require('aws-sdk');
    // Set region
    AWS.config.update({region: 'ap-southeast-2'});
    
    const sns = new AWS.SNS()
    
    module.exports.handler = async (event) => {
    
      const params = {
        Message: 'This is a sample message',
        Subject: 'Test SNS From Lambda',
        TopicArn: 'arn:aws:sns:ap-southeast-2:577913011449:TestTopic'
      };
    
      let response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
      };
      try {
        const data = await sns.publish(params).promise();
        response.messageId = data.MessageId,
        response.result = 'Success'
      } catch (e) {
        console.log(e.stack)
        response.result = 'Error'
      }
      return response
    
    };

If for whatever reason you don't want to use async/await, you then need to move the return of your function inside your .then() code, as well as return as soon as the promise is invoked, like this:

    'use strict';
    
    // Load the AWS SDK for Node.js
    var AWS = require('aws-sdk');
    // Set region
    AWS.config.update({region: 'ap-southeast-2''});
    
    // Create publish parameters
    var params = {
        Message: 'This is a sample message',
        Subject: 'Test SNS From Lambda',
        TopicArn: 'arn:aws:sns:ap-southeast-2:577913011449:TestTopic'
    };
    
    module.exports.handler = async (event) => {
      
      // Create promise and SNS service object
      var publishTextPromise = new AWS.SNS().publish(params).promise();
    
      let response = {
          statusCode: 200,
          body: JSON.stringify('Hello from Lambda!'),
      };
    
      // Handle promise's fulfilled/rejected states
      return publishTextPromise.then(
          function(data) {
              console.log("Message ${params.Message} send sent to the topic ${params.TopicArn}");
              console.log("MessageID is " + data.MessageId);
              response.result = 'Success';
              return response;
          }).catch(
              function(err) {
              console.error(err, err.stack);
              response.result = 'Error';
              return response
          });
    
    };

I highly recommend you go with approach #1 though.