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[bug] limit bootstrap room to to [0, 2^63 - 1] #8684

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Merged
merged 1 commit into from
Aug 1, 2025
Merged

[bug] limit bootstrap room to to [0, 2^63 - 1] #8684

merged 1 commit into from
Aug 1, 2025

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slin1237
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@slin1237 slin1237 commented Aug 1, 2025

Motivation

This PR fixes a critical bug in the PD (Prefill-Decode) router that causes KVTransferError and server hangs when routing requests to disaggregated prefill and decode nodes. The error manifests as:

Decode transfer failed for request rank=0 decode_req.req.rid='9a8d4c5f3ebf4fb2a60c04ae4bfeb72e' 
decode_req.req.bootstrap_room=3217994150080674400 with exception 
KVTransferError(bootstrap_room=3217994150080674400): Aborted by AbortReq.

The issue occurs because the Rust PD router generates bootstrap_room values in the full unsigned 64-bit range (0 to 2^64 - 1), while the Python backend expects signed 64-bit values (0 to 2^63 - 1). This mismatch causes failures when bootstrap_room values exceed 2^63 - 1.

Modifications

  • sgl-router/src/routers/pd_types.rs: Fixed bootstrap_room generation to match Python's expected range

Checklist

@slin1237 slin1237 requested a review from ByronHsu as a code owner August 1, 2025 20:19
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Summary of Changes

Hello @slin1237, 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 resolves a critical KVTransferError and server hang issue in the Prefill-Decode (PD) router. The problem stemmed from a mismatch in bootstrap_room value ranges between the Rust-based router and the Python backend. The changes ensure that the Rust component now generates bootstrap_room values within the expected signed 64-bit range, improving the stability and reliability of the routing mechanism.

Highlights

  • Critical Bug Fix: Addressed a critical bug in the Prefill-Decode (PD) router that caused KVTransferError and server hangs. This was due to a mismatch in how bootstrap_room values were generated and expected by different components.
  • Data Type Compatibility: Ensured that the bootstrap_room values generated by the Rust PD router are now limited to the range [0, 2^63 - 1]. This aligns with the signed 64-bit integer expectation of the Python backend, resolving the KVTransferError.
  • New Unit Test: Introduced a new unit test (test_bootstrap_room_range) to rigorously verify that generated bootstrap_room values consistently fall within the correct [0, 2^63 - 1] range for both single and batch requests, preventing regressions.
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Code Review

This PR effectively addresses a critical bug by limiting the bootstrap_room value to the expected range. The changes are well-structured and include a new unit test for validation. I've suggested using i64::MAX for better readability and maintainability.

@zhyncs zhyncs self-assigned this Aug 1, 2025
@zhyncs zhyncs merged commit ab9b893 into main Aug 1, 2025
23 of 24 checks passed
@zhyncs zhyncs deleted the router-room-fix branch August 1, 2025 21:41
lifuhuang pushed a commit that referenced this pull request Aug 3, 2025
@slin1237 @lifuhuang
[bug] limit bootstrap room to to [0, 2^63 - 1] (#8684)
f238b9e
ShangmingCai pushed a commit that referenced this pull request Aug 5, 2025
@slin1237 @ssssnow
[bug] limit bootstrap room to to [0, 2^63 - 1] (#8684)
33684d5
ShangmingCai pushed a commit that referenced this pull request Aug 5, 2025
@slin1237 @ssssnow
[bug] limit bootstrap room to to [0, 2^63 - 1] (#8684)
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@slin1237 slin1237 mentioned this pull request Aug 6, 2025
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narutolhy pushed a commit to narutolhy/sglang that referenced this pull request Aug 17, 2025
@slin1237 @narutolhy
[bug] limit bootstrap room to to [0, 2^63 - 1] (sgl-project#8684)
afa497b
narutolhy pushed a commit to narutolhy/sglang that referenced this pull request Aug 18, 2025
@slin1237 @narutolhy
[bug] limit bootstrap room to to [0, 2^63 - 1] (sgl-project#8684)
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@zhyncs zhyncs zhyncs approved these changes

@ByronHsu ByronHsu Awaiting requested review from ByronHsu ByronHsu is a code owner

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