[Misc] Add type alias ReqId and EngineId for better readability

[lk-chen]

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

Purpose

Improve readability, otherwise hard to justify wether the key of a dict is requests_id or engine_id at first glance.

Test Plan

trivial change, rely on existing unit test

Test Result

(Optional) Documentation Update

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @lk-chen, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request primarily aims to enhance the readability and maintainability of the codebase by introducing and consistently applying specific type aliases for string identifiers. By clearly distinguishing between request IDs and engine IDs through ReqId and EngineId type hints, the changes make the code's intent more transparent, especially in areas dealing with distributed KV transfer metadata.

Highlights

• Type Aliases Introduction: Introduced ReqId and EngineId as new type aliases for str within vllm/distributed/kv_transfer/kv_connector/v1/nixl_connector.py to enhance code clarity.
• Improved Readability: Applied the newly defined ReqId and EngineId type aliases across various dictionary keys and variable annotations in nixl_connector.py. This change makes the intent of string identifiers (whether they represent request IDs or engine IDs) explicit, significantly improving code readability and maintainability.
• Minor Code Refinements: Added an assertion to ensure vllm_config.kv_transfer_config.engine_id is not None and included an explicit int type hint for self.side_channel_port.

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[gemini-code-assist]

Code Review

This pull request introduces type aliases ReqId and EngineId for str, aiming to improve code readability by making it clearer when a string represents a request ID or an engine ID. This is a good practice that enhances code maintainability.

Overall Assessment:

The changes are well-implemented and achieve the stated goal. The new type aliases are consistently applied in the modified code sections. The code adheres to common Python best practices, including PEP 8 for type alias naming (CapWords).

Key Changes and Observations:

• Type Aliases: The introduction of EngineId = str and ReqId = str is the core of this PR. These aliases are used to update type hints in various dictionary keys and variable declarations, which significantly clarifies their purpose.
• Readability: The primary goal of improving readability is successfully met. It's now easier to understand the intended type of string identifiers at a glance.
• Correctness:
  • The changes are primarily refactoring through type aliases and do not alter the underlying logic. Runtime behavior should remain unchanged.
  • An important assertion assert vllm_config.kv_transfer_config.engine_id is not None was added in NixlConnector.__init__. Given that KVTransferConfig.engine_id is Optional[str] and the new EngineId alias is str (non-optional), this assertion is crucial for type safety. It ensures that self.engine_id is never assigned None, which would violate its EngineId type hint. This is a good addition for robustness.
  • The removal of explicit str() conversions for engine_id (which is now typed as EngineId) is correct.
• Maintainability: The changes improve code clarity and make it easier to understand the roles of different string identifiers.
• Testing: The author relies on existing unit tests, which is generally acceptable for this type of refactoring, assuming good test coverage.

No issues of medium, high, or critical severity were identified in the changed code. The pull request is a positive contribution to the codebase.

[lk-chen]

distributed-tests-4-gpus already failing on nightly build and unrelated to this PR

@njhill could you take a quick review?