Handing back a response to API Gateway from Lambda

Question

I'm using API Gateway-to-Lambda for a few micro-services but in at least one case the service will take 20-30 seconds to complete so in cases like this I'd like to pass back an immediate response to the client, something like:

 status: 200
 message: {
      progressId: 1234
 }

and then allow the Lambda Function to continue on (and periodically updating the "processId" somewhere that is accessible to a client. The problem is that if you call context.succeed(), context.fail(), or context.done() that apparently stops the lambda function from further execution and yet it's the only way I know to flush the stdout buffer back to the API Gateway.

This has led me to a second approach which I haven't yet try to tackle (and for simplicity sake would love to avoid) which involves API Gateway calling a "Responder" Lambda function that then asynchronously fires off the Microservice and then immediately responds to the API Gateway.

I've tried to illustrate these two options in sketch format below. I'd love to hear how anyone's been able to solve this problem.

How did you end up resolving this?

systemdebt
– systemdebt

2023-01-04 22:38:55 +00:00
Commented Jan 4, 2023 at 22:38 — systemdebt
– systemdebt, Commented Jan 4, 2023 at 22:38

Bob Kinney · Accepted Answer · 2015-11-23 17:49:23Z

7

Currently API Gateway requires that the AWS Lambda integration is synchronous. If you desire asynchronous invocation of your Lambda function, you have 2 options:

Invoking the Lambda asynchrously, either with an AWS integration calling InvokeAsync on Lambda, or using an intermediate service such as SNS or Kinesis to trigger the Lambda function.
You're #2 diagram, using a synchronous Lambda invoke to initiate the asynchronous invoke.

answered Nov 23, 2015 at 17:49

Bob Kinney

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ken Over a year ago

Ok, that's what I figured but it's good to hear it from someone who knows. Thanks.

Marko Kudjerski · Accepted Answer · 2016-06-18 19:32:36Z

5

As of Apr/2016 is it is possible to create async Lambda execution through API Gateway by using AWS Service Proxy. See http://docs.aws.amazon.com/apigateway/latest/developerguide/integrating-api-with-aws-services-lambda.html

answered Jun 18, 2016 at 19:32

Marko Kudjerski

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Sergey Lyapustin Over a year ago

Are someone able to call Lambda in async mode? It seems this doc is outdated with current AWS Gateway/Lambda interface.

Alonimus · Accepted Answer · 2017-09-05 22:23:06Z

2

You can send the X-Amz-Invocation-Type header, it supports async calls through the Event value

You can optionally request asynchronous execution by specifying Event as the InvocationType

http://docs.aws.amazon.com/lambda/latest/dg/API_Invoke.html#API_Invoke_RequestSyntax

Also, if you can't send it via your micro-service, you can configure this header to be passed by default through the Method Execution -> Integration Request -> HTTP Headers in your API Gateway Resource

This worked for me on a micro-service -> API Gateway -> Lambda scenario, like the mentioned on the question.

answered Sep 5, 2017 at 22:23

Alonimus

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