Break PostResponse requestcontrol plugin into 3 separate plugins to add streamed request functionality

[BenjaminBraunDev]

/kind bug
/kind feature

What this PR does / why we need it:
PostResponse runs at the first chunk received instead of at the end of the request, however some PostResponse plugins would like to run only when a request is fully complete. This PR allows that flexibility by breaking out PostResponse into 3 separate requestcontrol plugin hooks for when the response is received, each chunk streamed, and fully complete respectively. The requestcontrol plugins are now the following:

PreRequest
PostResponseReceived
PostResponseStreamed
PostResponseComplete

Which issue(s) this PR fixes:
Fixes #1483

Does this PR introduce a user-facing change?:

PostResponse plugin has been renamed to PostResponseReceived

[netlify]

✅ Deploy Preview for gateway-api-inference-extension ready!

Name	Link
🔨 Latest commit	f73ef27
🔍 Latest deploy log	https://app.netlify.com/projects/gateway-api-inference-extension/deploys/68e41b3f1338220008206ec1
😎 Deploy Preview	https://deploy-preview-1661--gateway-api-inference-extension.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[k8s-ci-robot]

Hi @BenjaminBraunDev. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[ahg-g]

/ok-to-test

[kfswain]

Some smaller comments, overall looks good. Thanks!

/approve

[nirrozenbaum]

please remove logger from the args, we don't use logr as argument to functions, we use contextual logging.
for example

log.FromContext(ctx).V(logutil.TRACE).Info(....)

see for example here:

gateway-api-inference-extension/pkg/epp/requestcontrol/director.go

Line 171 in 75b2144

loggerTrace := log.FromContext(ctx).V(logutil.TRACE)

[kfswain]

I asked him to remove that, in the streaming case the high volume of instantiations of the logger will cause allocation/gc pressure. Luke mentioned this as an optimization during flow control benchmarking, and i think the same applies here b/c there will be multiple streaming calls per request.

[BenjaminBraunDev]

Does log.FromContext(ctx).V(logutil.TRACE).Info(....) actually make another logger? I would think it takes the logger "from the context" given ctx has a logger. Does it actually allocate more memory? I would think that pretty inefficient.

From the FromContext() in go-logr package:

// FromContext returns a Logger from ctx or an error if no Logger is found.

[nirrozenbaum]

@BenjaminBraunDev made another iteration on the PR.
overall it looks good. the main point I was highlighting in the review is mainly around keeping consistency and use contextual logging.
otherwise the PR lgtm.

[kfswain]

/approve

Thanks Ben! Will let Nir give final stamp

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BenjaminBraunDev, kfswain

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [kfswain]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment