Java support?

[jplock]

Should it be possible to support Java-based lambdas with this?

[mhart]

@jplock yep, it absolutely is – as it says in the README Java exists on the images, so you can run things manually yourself – I just haven't written a Java test runner yet.

I'll comment here when I have 👍

[utkuturunc]

I have three questions.

Has there been any progress on this?
Will it be possible to test Scala apps?
How could I help implementing Java support?

[mhart]

No progress – creating a Java runner is a different challenge to the others because it's not a dynamic target.

You can run Java (and hence Scala) in any of the images – the binaries and libraries exist on the base image, there's just no mock Lambda runner.

Creating a mock Lambda runner would involve replicating what has been done in the other languages (Python, Node.js) – essentially keeping as much as possible of the in-built Lambda runner and just swapping out the core invoker with a mock implementation.

[utkuturunc]

My goal is to use the following plugin in order to simulate scala microservices. As far as I understood, I need the runners.

https://github.com/serverless-community-labs/serverless-plugin-simulate

[mhart]

Probably – yep. Not entirely sure how they use docker-lambda but I imagine they're relying on the mock runners.

[timve]

I have been working on adding java8 support to docker lambda, see master...timve:java8 for the diff. It basically consists of two java processes:

• a starter that sets up the environment and starts a separate JVM process where the lambda is invoked
• an executor that sets up the context and can invoke the lambda

I would have liked to have used the actual lambda runner code from AWS in order to come closer to the real deal, but I run into issues with the native part of it.

The two main todo's are:

• mimic the AWS lambda in unpacking jar / zip archive before running
• setup remote debugging support (actually works, but requires the -Xshare:on option to be disabled)

It is not tested yet, the example java lambda code runs but I have not tested more complex scenarios yet.

Is this something that you would consider to add to docker-lambda ?

[mhart]

@timve – I've actually been working on a Java runner myself – I should've updated this issue. It's slightly separate from your approach I think in that I use the production runner jar, but I just swap out the class in the jar that communicates with the native library with a mock class.

Hopefully I'll have time in the next week to push something up – and I'll check out your solution too.

Thanks!

[timve]

@mhart Ah, sounds good, swapping out the native part with a mock sounds a bit closer to the real environment compared to my solution.
Interested to see what you have come up with, let me know if you require any help.

[mhart]

@timve finally got time to pushing my stuff up: #48

The example there in the PR description should work currently (lambci/lambda:java8 is up on Docker hub)

[timve]

@mhart Thanks, neat little trick swapping out the LambdaRuntime class in the jar ;-). I will try give it a spin in the next couple of days.

[mhart]

@timve yeah, now if only it were as easy for .NET DLLs – then I could support the dotnetcore1.0 runtime too! 😉

[pallavi2146-zz]

Right now container(lambci/lambda:java8) running in my machine. Wants to debug in intellij idea. how can i do that. Kindly help me.