[V1][P/D]Support automatic instance removal after crash for P2pNcclConnector

[Abatom]

Support automatic instance removal after crash for P2pNcclConnector

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @Abatom, 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 enhances the resilience and stability of the P2pNcclConnector by introducing mechanisms for automatic detection and removal of unresponsive or crashed instances. It achieves this through a combination of timestamp-based health checks in the proxy, robust NCCL communication timeouts, and a connection blacklisting strategy, ensuring smoother operation in distributed environments.

Highlights

• Automatic Instance Cleanup: The disagg_prefill_proxy_xpyd.py now tracks prefill_instances and decode_instances with timestamps. It automatically removes instances from its registry if their last known 'ping' (registration) is older than DEFAULT_PING_SECONDS, effectively cleaning up crashed or unresponsive instances.
• NCCL Communication Timeout & Abort: Implemented a _with_timeout wrapper for NCCL send and receive operations in p2p_nccl_engine.py. This wrapper uses a ThreadPoolExecutor to monitor operations and calls ncclCommAbort if an NCCL operation exceeds nccl_timeout_s, preventing indefinite hangs.
• Connection Blacklisting: A new address_black_list is introduced in P2pNcclEngine to temporarily store addresses of failed connections. Subsequent connection attempts to blacklisted addresses are prevented for a defined period, reducing retries to unresponsive peers.
• ZMQ Send Timeout: ZMQ sockets used for establishing NCCL connections (_get_connect) are now configured with a SNDTIMEO option, preventing ZMQ send calls from blocking indefinitely during connection setup.
• NCCL Abort API Exposure: The pynccl_wrapper.py now exposes the ncclCommAbort function, allowing the P2pNcclEngine to programmatically terminate hung NCCL communicators.

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[gemini-code-assist]

Code Review

The pull request introduces automatic instance removal after a crash for the P2pNcclConnector. It adds timeout mechanisms for NCCL operations, blacklisting of addresses after failures, and pinging to maintain connections. The changes aim to improve the robustness and reliability of distributed KV cache transfer.