Add code for Envoy extension that support body-to-header translation

[rramkumar1]

Ref: #321

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[k8s-ci-robot]

Hi @rramkumar1. Thanks for your PR.

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[ahg-g]

/ok-to-test

[hzxuzhonghu]

I am not sure how it is related with this project. I mean you can deploy this not depending on gateway inference extension

[rramkumar1]

I am not sure how it is related with this project. I mean you can deploy this not depending on gateway inference extension

@hzxuzhonghu Sorry I forgot to link the related issue in the initial comment. Fixed that.

[hzxuzhonghu]

Thanks, now i get the inetention. But i am wondering, should we separate it from the ext-proc binart? IMO, it can be merged into the current binary. Correct me if miss some ctx

[rramkumar1]

Thanks, now i get the inetention. But i am wondering, should we separate it from the ext-proc binart? IMO, it can be merged into the current binary. Correct me if miss some ctx

I think it should be a separate binary because this particular extension is intended to execute before the routing decision while endpoint picker is intended to execute after routing decision.

[hzxuzhonghu]

hmm, the model name header will be used by the http route match later. What confused me most is the epp currenlty only support one model pool. It seems no model match needed to specify in the HTTPRoute

[robscott]

hmm, the model name header will be used by the http route match later. What confused me most is the epp currenlty only support one model pool. It seems no model match needed to specify in the HTTPRoute

@hzxuzhonghu for a bit more context, there are different points in time where we can attach an ext_proc extension. We want to attach this extension early in the process so it can add headers before routing logic is computed. That would allow someone to say that requests for the "foo" model should go to the "bar" InferencePool while requests for "baz" model should go to a different InferencePool.

Then when the request gets to an InferencePool, the Endpoint Picker extension can select the best endpoint to serve a request for that model within that InferencePool.

[hzxuzhonghu]

Ah, that makes sense. Would we plan to support multiple inferencepool within a epp process

[robscott]

Ah, that makes sense. Would we plan to support multiple inferencepool within a epp process

That's definitely been a point of discussion, I think it's inevitable that that will be a mode at some point, but it's not part of the initial releases. The rationale for this is:

1. We're currently relying on very frequent probing of every endpoint an EPP is supporting, this would not scale well to a large number of endpoints
2. We're relying on keeping some state in memory, this would also not scale to a large number of endpoints
3. Having a 1:1 mapping between InferencePool and EPP allows you to effectively traffic split between different EPPs or InferencePools

With all that said, I think these could all be temporary limitations.

[robscott]

Thanks @rramkumar1! Once we get the image pipeline set up and some corresponding docs, this will be a great part of the v0.2 release.

[robscott]

@kfswain Are you able to help get automated builds set up for this image as well? Can't remember all the steps required offhand

[ahg-g]

See #320 as an example; we a added build rule and a step in cloudbuild to automatically create the image for the lora syncer sidecar

[ahg-g]

Can you also please add a README.md file; I added one for pkg/epp at #386

[k8s-ci-robot]

@rramkumar1: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-gateway-api-inference-extension-verify-main	5f6daff	link	true	/test pull-gateway-api-inference-extension-verify-main

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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