Not being able to connect to MongoDB from AWS Lambda

0
votes

I am trying to build an alexa skill that connects to mlab when requested. I have put multiple console.log() messages in my code and observed that the console inside

db.once('open', function callback() { console.log('a');}) is not getting executed.

When looking up the CloudWatch logs, i get this message:

REPORT RequestId: 1b57c8f8-61b6-11e8-9038-5fc7c131d222 Duration: 40.54 ms Billed Duration: 100 ms Memory Size: 128 MB Max Memory Used: 51 MB

I have used the standard connection statements as prescribed by mongoose:

"use strict";
var Alexa = require("alexa-sdk");
const mongoose = require("mongoose");
var handlers = {

'LanguageIntent': function () {
  let uri = 'mongodb://my_uri';
  mongoose.connect(uri);
  let speechOutput;
  let db = mongoose.connection;
  db.on('error', console.error.bind(console, 'connection error:'));

  db.once('open', function callback() {
    console.log("I AM HERE");
  });
  console.log("Outside");
 }
}
exports.handler = function(event, context, callback){
  var alexa = Alexa.handler(event, context);
  alexa.registerHandlers(handlers);
  alexa.execute();
};

As far as I understand, The request is NOT getting timed out, and there must be some other problem that I can't understand. The cloudwatch log doesn't show "I AM HERE". But "Outside" gets recorded in the logs. This makes me think that there must be some problem while establishing a connection.

Any help in this regard would be highly appreciated!

2
mongodbaws-lambdaalexaalexa-skills-kit
You need to verify that you can actually reach the instance from the location as your first priority. Calling mongoose.connect() without using a promise resolve or callback is not really recommended. See Connections in the mongoose documentation for more detail. Also instead of "psuedocode" you should provide a "complete" simple listing which merely confirms the connection as the issue. See How to create a Minimal, Complete, and Verifiable example – Neil Lunn
As stated, "first priority" is to actually look and see if connections are possible between the service and the hosted MongoDB instance. This involves verifying the network settings with Mlab to ensure your remote host is allowed and that you can also connect from any other location. Same goes for the AWS Lambda, by ensuring that everything else works with a minimal "hello world" as well as then verifying that it can talk to external hosts. Put all the detail into your question. This is not something others can really "debug" other than pointing out things missing. So show everything. – Neil Lunn

2 Answers

0
votes

As per your shared code, If connection details and everything is correct then you can by increasing the timeout value, because for the first time connection establishment it might take longer then usual query. It doesn't affect anything. Once it work with me.

0
votes

After a week of debugging sprints, I found the answer to my problem. My code was of the format: 

"use strict";
var Alexa = require("alexa-sdk");
const mongoose = require("mongoose");
var handlers = {
'LanguageIntent': function () {
  let uri = 'mongodb://my_uri';
  mongoose.connect(uri);
  let speechOutput;
  let db = mongoose.connection;
  db.on('error', console.error.bind(console, 'connection error:'));

  db.once('open', function callback() {
   console.log("I AM HERE");
  });
  console.log("Outside");
  this.response.speak("HI");
  this.emit(':responseReady');
}
exports.handler = function(event, context, callback){
  var alexa = Alexa.handler(event, context);
  alexa.registerHandlers(handlers);
  alexa.execute();
};

I noticed that the moment I moved my reponse.speak code INSIDE the db.once function, it started working seamlessly. Therefore, the correct way to structure the code is: 

db.once('open', function callback() {
   this.response.speak("HI");
   this.emit(':responseReady');
});