Lambda destination for other Lambda is not invoked

Question

Hello,

In the diagram below the Lambda Function L2 is a successful asynchronous destination for Lambda Function L1.   
![Enter image description here](/media/postImages/original/IMt1xHW0cdQoafF45oAyqCKw)

When the event comes from SQS, L2 is not invoked.   
When the event comes from S3, L2 is invoked.  
When event comes from Actor that test in Lambda screens from Management Console, L2 is not invoked.   
When L1 is invoked from L3 using asynchronous invocation,  L2 is not invoked.

```
 private AWSLambdaAsync lambda = null;
    
    public LambdaFunctionHandler() {
    	lambda = AWSLambdaAsyncClientBuilder.standard()
    			.withRegion(Regions.US_EAST_2)
    			.build();
    }
Future future_res = lambda.invokeAsync(req);
```
Could you please explain the above behaviours ? Is the L2 invocation related to how the event is sent to L1 (synchronous/ asynchronous) ?

Could you please specify how to send SQS events so that L2 to be invoked ?

Thank you,   
Mihai ADAM

Accepted Answer

Hi,

you are seeing this behavior because the Lambda function L2 is configured as a successful **asynchronous** destination. That means, it is only invoked when the initial invoke was a async request. So, in your case,

* The invoke from the user is done **synchronously**, therefore the destination is not triggered
* When SQS is used as a event source, Lambda polls the queue and invokes your Lambda function **synchronously** (see https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html), therefore the destination is not triggered
* For the code that you shared, make sure to set the `InvocationType` to `Event`, see https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/lambda/model/InvokeRequest.html#setInvocationType-com.amazonaws.services.lambda.model.InvocationType-

Basically, the destination is only invoked for asynchronous requests.

To add some context: The primary use case of Destinations is to know about the async execution results of Lambda functions, primarily to get more visibility into the execution details like request and response contexts, payloads, exception stack traces and so on.

Lambda destination for other Lambda is not invoked

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