AWS lambda function stops working after timed out error

Question

I have a simple lambda function that asynchronously makes an API calls and then returns data. 99% of the time this works great. When ever the API takes longer then the lambda configured timeout, it gives an error as expected. Now the issue is that when I make any subsequent calls to the lambda function it permanently gives me the timeout error.

 "errorMessage": "2016-05-14T22:52:07.247Z {session} Task timed out after 3.00 seconds" 

In order to test that this was the case I set the lambda timeout to 3 seconds and have a way to trigger these two functions within the lambda.

Javascript

function now() {      return response.tell('success');  }  function wait() {     setTimeout(function() { return response.tell('success'); }, 4000); } 

When I call the now function there are no problems. When I call the wait function I get the timeout error and then any subsequent calls to now give me the same error.

Is this an expected behavior? I would think that any subsequent calls to the lambda function should work. I understand I can always increase the configuration timeout, but would rather not.

Answer 1

You should look for how your function handle works with a specific context.callbackWaitsForEmptyEventLoop

If that boolean-type is false, the setTimeout won't be ever fired, because you might've answered/handled the lambda invocation earlier. But if the value of callbackWaitsForEmptyEventLoop is true - then your code will do what you are looking for.

Also - it's probably easier to handle everything via callbacks directly, without the need for "hand-written" timeouts, changing configuration timeouts and so on...

E.g.

function doneFactory(cb) { // closure factory returning a callback function which knows about res (response)   return function(err, res) {     if (err) {       return cb(JSON.stringify(err));     }     return cb(null, res);   }; }  // you're going to call this Lambda function from your code exports.handle = function(event, context, handleCallback) {    // allows for using callbacks as finish/error-handlers   context.callbackWaitsForEmptyEventLoop = false;    doSomeAsyncWork(event, context, doneFactory(handleCallback)); };