[Cherry-Pick] Support for request-level speculative decoding metrics monitoring.(#5518)

[Deleter-D]

Motivation

💡 If this PR is a Cherry Pick, the PR title needs to follow the format by adding the [Cherry-Pick] label at the very beginning and appending the original PR ID at the end. For example, [Cherry-Pick][CI] Add check trigger and logic(#5191)

💡 如若此PR是Cherry Pick，PR标题需遵循格式，在最开始加上[Cherry-Pick]标签，以及最后面加上原PR ID，例如[Cherry-Pick][CI] Add check trigger and logic(#5191)

Support for request-level speculative decoding metrics monitoring.

Modifications

Support for request-level speculative decoding metrics monitoring, with key metrics returned via API. The return format is as follows: for streaming output, metrics will be returned in the final streaming packet, while other streaming packets will be null.

{
    "id": "xxx",
    "model": "xxx",
    "choices": [
        {
            ...
            "speculate_metrics": {
                "accepted_tokens": 128,
                "rejected_tokens": 112,
                "accept_ratio": 0.53125,
                "average_accept_length": 2.1333333333333333,
                "accept_ratio_per_head": [
                    0.6,
                    0.6388888888888888,
                    0.391304347826087
                ]
            }
        }
    ],
    ...
}

Usage or Command

Accuracy Tests

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 65.38462% with 27 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/2.4@c19af49). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/output/token_processor.py	48.88%	20 Missing and 3 partials ⚠️
fastdeploy/engine/request.py	60.00%	2 Missing ⚠️
...astdeploy/entrypoints/openai/serving_completion.py	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             release/2.4    #5614   +/-   ##
==============================================
  Coverage               ?   59.00%           
==============================================
  Files                  ?      327           
  Lines                  ?    40721           
  Branches               ?     6185           
==============================================
  Hits                   ?    24028           
  Misses                 ?    14829           
  Partials               ?     1864           

Flag	Coverage Δ
GPU	59.00% <65.38%> (?)

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