fix: Add explicit [DONE] signal to SSE stream endpoint

[DineshThumma9]

Fixes issue where /run_sse endpoint sometimes fails to close the SSE connection after the model's final response, causing client-side hangs.

Changes:

• Add 'data: [DONE]' termination signal after all events streamed
• Send [DONE] in error path as well for consistency
• Update test to filter out [DONE] signal
• Run autoformat.sh for code style compliance

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: #issue_number
• Related: Intermittent: /run_sse SSE connection sometimes does not close after final model response #4216

Problem:
SSE Events don't send explicit done or any kind of termination signal which results client side guessing
or hanging for termination signal

Solution:
I have added data:[DONE] event after end of sse
So client know what event to check on termination

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

All test case passes

Manual End-to-End (E2E) Tests:
I have tested locally using local models and passed

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

[gemini-code-assist]

Summary of Changes

Hello @DineshThumma9, 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 significantly improves the reliability of Server-Sent Events (SSE) by implementing a clear termination signal. Previously, clients could experience hangs due to the lack of an explicit end-of-stream indicator. By adding a 'data: [DONE]' message, the system now provides a robust mechanism for clients to detect when an SSE stream has concluded, whether successfully or due to an error, thereby enhancing the overall stability and user experience of streaming data.

Highlights

• Explicit SSE Stream Termination: Introduced an explicit 'data: [DONE]' signal to the Server-Sent Events (SSE) stream endpoint to clearly indicate the end of a stream, resolving client-side hanging issues.
• Consistent Error Handling: The 'data: [DONE]' termination signal is now also sent in error paths, ensuring consistent stream closure regardless of success or failure.
• Test Updates: Unit tests for SSE streaming have been updated to correctly filter out the new 'data: [DONE]' signal when parsing events.
• Code Style Compliance: The entire codebase was autoformatted using 'autoformat.sh' to maintain consistent code style.

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[DineshThumma9]

/gemini review

[gemini-code-assist]

Code Review

The pull request introduces an explicit data: [DONE] termination signal to the SSE stream endpoint, which is a crucial improvement for preventing client-side hangs by clearly indicating the end of the stream. This signal is correctly implemented in both successful and error paths, enhancing the robustness of the SSE connection handling. The corresponding unit test has also been appropriately updated to account for this new termination signal. Additionally, several minor stylistic changes, such as reformatting long string literals and removing redundant parentheses, have been applied across various files, contributing to better code readability and consistency.

[gemini-code-assist]

Code Review

This pull request addresses an issue where the /run_sse endpoint sometimes failed to close SSE connections, leading to client-side hangs. The fix involves adding an explicit data: [DONE] termination signal after all events have been streamed, including in error paths, to ensure consistent connection closure. The changes also include updates to the relevant test cases to filter out this new [DONE] signal, and the codebase has been autoformatted for style compliance. The changes are well-aligned with the problem description and provide a robust solution for reliable SSE stream termination.