[Cherry-Pick][BugFix] Seperate prometheus multiproc dir for single-server multi-dp services (#8059)

[liyonghua0910]

Motivation

Fix metric interference when multiple data-parallel services run on one server by isolating Prometheus multiprocess files per DP rank.

Modifications

• Track the original PROMETHEUS_MULTIPROC_DIR set during metrics initialization.
• Add setup_dp_prometheus_dir() to create per-DP dp{i} subdirectories and switch the target environment.
• Apply DP-specific Prometheus dirs when launching internal-adapter DP services from LLMEngine / EngineService and when multi_api_server starts per-DP API server processes.
• Update unit tests for multi API server Prometheus dirs, Prometheus setup behavior, cache transfer setup, and graph optimization metadata.

Usage or Command

N/A

Accuracy Tests

N/A

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.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.67568% with 9 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/online/20260415@eb7ea99). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/engine/engine.py	16.66%	5 Missing ⚠️
fastdeploy/engine/common_engine.py	33.33%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##             release/online/20260415    #8062   +/-   ##
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  Coverage                           ?   71.94%           
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  Files                              ?      389           
  Lines                              ?    54539           
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  Hits                               ?    39238           
  Misses                             ?    12585           
  Partials                           ?     2716           

Flag	Coverage Δ
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[PaddlePaddle-bot]

🤖 Paddle-CI-Agent | ci_status_monitor | 2026-06-26 11:44:30 UTC+08:00

CI报告基于以下代码生成（30分钟更新一次）:
PR commit: c4788ec0 | Merge base: eb7ea99 (branch: release/online/20260415)

---

1 Required任务 : 7/7 通过

总执行（rerun次数）	总任务	✅ 通过	❌ 失败	⏳ 运行中	⏸️ 等待中	跳过
20(0)	20	20	0	0	0	0

无

2 失败详情

无

outdated

[PaddlePaddle-bot]

🤖 Paddle-CI-Agent | pr_review | 2026-06-23 19:34:02

📋 Review 摘要

PR 概述：为单机多 DP 服务拆分 Prometheus multiprocess 目录，并补充相关测试修复。
变更范围：fastdeploy/metrics/、fastdeploy/engine/、fastdeploy/entrypoints/openai/、相关单测。
影响面 Tag：[Engine] [APIServer]

问题

级别	文件	概述
-	-	未发现新的阻塞性问题。PR 规范问题在下面章节报，不在这里重复

历史 Findings 修复情况

Finding	问题	状态
F1	setup_dp_prometheus_dir() 被 multi_api_server 用于 Popen 子进程时，dp_id == 0 仍会迁移 base 目录下已有 .db 文件。	⚠️ 仍存在

📝 PR 规范检查

标题格式已补充 [Cherry-Pick][BugFix] 和原 PR 号；描述仍保留模板占位，Motivation / Modifications / Usage or Command / Accuracy Tests 未填写。

PR 描述建议（点击展开，可直接复制）

## Motivation
Fix metric interference when multiple data-parallel services run on one server by isolating Prometheus multiprocess files per DP rank.

## Modifications
- Track the original `PROMETHEUS_MULTIPROC_DIR` set during metrics initialization.
- Add `setup_dp_prometheus_dir()` to create per-DP `dp{i}` subdirectories and switch the target environment.
- Apply DP-specific Prometheus dirs when launching internal-adapter DP services from `LLMEngine` / `EngineService` and when `multi_api_server` starts per-DP API server processes.
- Update unit tests for multi API server Prometheus dirs, Prometheus setup behavior, cache transfer setup, and graph optimization metadata.

## Usage or Command
N/A

## Accuracy Tests
N/A

## Checklist

- [x] 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.
- [x] 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.

总体评价

核心改动围绕 Prometheus multiprocess 目录隔离展开，本轮未发现新的阻塞性代码问题。历史 F1 在当前 diff 中仍未修复，建议后续把 multi_api_server 的纯环境派生逻辑与 DP0 .db 迁移逻辑拆开，避免 launcher 阶段误迁移文件。