== Why is this an issue?

Invoking other Lambdas synchronously from a Lambda is a scalability anti-pattern. Lambdas have a maximum execution time before they timeout (15 minutes as of May 2021). Having to wait for another Lambda to finish its execution could lead to a timeout.


A better solution is to generate events that can be consumed asynchronously by other Lambdas.


=== Noncompliant code example

With AWS SDKv1

[source,java]
----
InvokeRequest invokeRequest = new InvokeRequest()
         .withFunctionName("myFunction");

AWSLambda awsLambda = AWSLambdaClientBuilder.standard()
		.withCredentials(new ProfileCredentialsProvider())
		.withRegion(Regions.US_WEST_2).build();

awsLambda.invoke(invokeRequest); // Noncompliant
----


== Resources

* https://docs.aws.amazon.com/lambda/latest/dg/best-practices.html[Best practices for working with AWS Lambda functions]


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'''
== Implementation Specification
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=== Message

Avoid synchronous calls to other lambdas


=== Highlighting

Function invocation


'''
== Comments And Links
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=== on 27 May 2021, 14:13:15 Janos Gyerik wrote:
To be precise, I think the title should mention "synchronously": Lambdas should not invoke other lambdas _synchronously_


The description suggests 2 alternatives. I would drop the 2nd suggestion to make the call asynchronous, because I think it's generally not a good idea, due to tight coupling. The first idea is great, I'd mention only that: A better solution is to generate events that can be consumed asynchronously by other Lambdas.


 

=== on 27 May 2021, 14:23:37 Alexandre Gigleux wrote:
+1 with [~janos.gyerik]


I also suggest to rewrite "As the runtime of your function is bounded, waiting for another Lambda to finish executing could cause a timeout." like this:

"Lambdas have a maximum execution time before they timeout (15 minutes as of May 2021). Having to wait for another Lambda to finish its execution could lead to a timeout".

=== on 31 May 2021, 12:04:23 Quentin Jaquier wrote:
We review the suggestions together with [~dorian.burihabwa], it makes sense to us as well.


The remaining concern is that the compliant solution is not relevant anymore and we have a hard time coming up with a new one. [~janos.gyerik] do you have an example or a link to the documentation that could help?

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