feat: add support for ALB

[ihendriks]

Description

AWS ALB support lambdas, serverless supports them as well. As such, supporting them in serverless-offline seems logical.

Based on:

• Feature / add alb support #1250 by @bayoumymac
• https://github.com/tmaslen/serverless-local-alb-example by @tmaslen

Motivation and Context

Support for this has been requested by several people.

This would close #598 (which is already closed, but the feature is not supported).

How Has This Been Tested?

It's tested on our own project with success.

I was unable to get the testsuite to run at this time, but wanted to open the PR for feedback regardless.

[ihendriks]

@dherault I've rebased the PR and resolved the conflict.

Let me know if this needs further changes from my end. I've been using it locally for our usecase and haven't run into any issues so far.

[dnalborczyk]

@ihendriks thank you for fixing up the PR. at a quick glance, it looks great. it would be great if we could add some tests. even if you have some examples on usage, I could guide you on how to add those.

[ihendriks]

@dnalborczyk I've added an example and I've created some unittests. They're mostly duplicated from integrations/handlers as that made the most sense to me.

I didn't copy over everything, but figured this was a good starting point.

Let me know if there is anything that needs to be done.

Edit: Almost forgot to mention, but I noticed an issue where if you only define ALB endpoints (and no HTTP) in the serverless.yml, then it gets stuck during startup.
I'm not sure if that's an issue in my ALB code, or something else. Perhaps you know?

For now I've added a dummy HTTP endpoint in the unittests for ALB, but it's not the best solution.

[ihendriks]

@dnalborczyk I fixed some issues with CORS and with wildcard parameters for the path.

There's a lot of code that is similar or outright duplicate of http/HttpServer.js but I think refactoring is best left to you, since you know better what you want.

I'm certain that there are features missing, but I don't have enough time to work on this. I think any other features can be taken care off at a later stage.

[dnalborczyk]

thank you very much @ihendriks ! I'll try to make some time to have a deeper look very soon. stay tuned. I just wanna iron out some outstanding kinks in v9.

There's a lot of code that is similar or outright duplicate of http/HttpServer.js but I think refactoring is best left to you, since you know better what you want.

unfortunately there's a lot of duplicate code everywhere 😉 and often times with very few or no tests, so refactoring without breaking stuff isn't easy. it's just how the project grew organically over time. that's why I'm trying to pull new stuff in (ideally) only with tests. same applies for bug fixes. at least those cases won't break [again] in any future refactoring efforts.

[ihendriks]

Hi @dnalborczyk, I was wondering what the status of your refactoring is?

If I were to get this PR up to date with the current state of the repo, do you think this could be merged?

I'm reluctant to work on this while you're refactoring at the same time, but I would like to get this merged sooner rather than later, if that's possible.

Not to pressure you or anything, just curious about what the plan/timeline is here.

[dnalborczyk]

thank you for your patience @ihendriks !

yes, if you could fix the conflicts that would be great. In the meantime I will wait to change any files related to your PR.

If needed, we can flag the ALB event support as experimental if there's anything to be fleshed out further.

[ihendriks]

Alright, I will try to make some time for it this week.

've fixed some issues that we found ourselves, but I can imagine there's a couple of things I've missed still. So Experimental flag might be a good idea until there's a bit more feedback from other users.

[ihendriks]

@dnalborczyk Sorry for the delay, was hard to find time for this.

I've resolved all conflicts, fixed a few issues and updated the code to match your refactoring a bit better.

Let me know if there is anything else that needs to be done.

[dnalborczyk]

thank you for fixing up the PR @ihendriks !!

we should get it merged in the next coming days. I'm thinking to release this as semver major, in case someone had an own/or third party offline plugin for application load balancer support, which in turn would likely break things or cause potentially weird behavior - although one could make that argument for any new features.