RuntimeDependenciesLayer rebuilding on every API request

[envek]

RuntimeDependenciesLayer rebuilding on every API request

[justintilson]

One way I found that changes this behavior is to include the --warm-containers=EAGER flag when starting your local SAM API. Example:

sam local start-api --docker-network your-network --env-vars=env.json --warm-containers=EAGER

From: https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/sam-cli-command-reference-sam-local-start-api.html with some more relevant tidbits here: https://aws.amazon.com/blogs/compute/working-with-aws-lambda-and-lambda-layers-in-aws-sam/

[Envek]

That's weird! I don't remember such nasty behavior.

What is your SAM CLI version? It may be some SAM CLI bug…

[Patrick-Erichsen]

Hey @Envek sorry for the delay, I didn't see your reply come through.

$ sam --version

SAM CLI, version 1.29.0

[kurkle]

+1

sam --version  
SAM CLI, version 1.23.0

Edit: No change after updating to 1.31.0
Edit2: aws/aws-sam-cli#1630 (comment)

[tmbs]

+1

~ sam --version
SAM CLI, version 1.31.0

~ sw_vers
ProductName:	macOS
ProductVersion:	11.6
BuildVersion:	20G165

[jettandres]

+1 also. I'm kinda new to AWS SAM. Thank you sir @Envek for the ts template

~ sam --version        
SAM CLI, version 1.33.0

[semmgeorge]

+1
SAM CLI, version 1.29.0

[moretalk]

+1
SAM CLI, version 1.35.0

[ahurlburt]

Seems like the workaround for

--warm-containers=EAGER

Does stop the containers rebuilding the layer each time. This is interesting as the docs (cli ref) imply there would be no difference between EAGER and LAZY with regards to layer rebuilding.

While this is helpful it's not great since a lot of times I am only testing a subset of lambdas and don't need the others to invoke at all (or build). Warming all of them still slows down dev process which is what sam local is intended to help with.

This related ticket implies to solve this one would need to publish the lambda and then reference via ARN: aws/aws-sam-cli#1630

IMO this isn't really a great solution since i want SAM to build the layer for me. I use sam so i can have everything in one place and a reproducible build.

I believe the reason to rebuild the layer is because sam needs to check if anything changed. However, i think practically speaking it would be a better solution to assume the layers do not change like the templates and in the event of a layer update sam local would need to be restarted. I think realistically most people want watch type behaviour for their lambda code and not so much the layers which is either shared libs or dependencies.

I also get a lot of errors using the EAGER warm flag, once I start making changes to the code some of the containers don't seem to exit properly and it causes sam local to crash. Then i need to start everything up again which leads me back to why I don't like having to warm everything to avoid the lambda layer rebuild...

[Envek]

This is great research, @ahurlburt!

Please open issue in https://github.com/aws/aws-sam-cli with this text so SAM CLI developers can be aware of it and hopefully will fix it some day.

[ahurlburt]

@Envek done: aws/aws-sam-cli#3725

Maybe people coming across this can upvote :)