The assertion `assert RequestStatus.is_finished(req.status)` at
scheduler.py:2109 fires when a partial-remote-prefill request
receives `finished_recving` while in RUNNING state (local prefill
already started before RDMA read completed).
This was the root cause of 67% error rate: EngineCore crashed with
"fatal error" assertion, killing the vLLM instance.
Fix: Replace assertion with debug log for non-WAITING, non-finished
requests. kv_both no-offload baseline confirmed 0 errors, proving
the crash was from our scheduler patch, not kv_both instability.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Complete implementation of direct RDMA read for KV cache migration:
vLLM Mooncake connector (mooncake_connector.py):
- PullReqMeta: add direct_read flag + block_hashes
- MooncakeConnectorMetadata: add hash_table_updates/removals for
scheduler->worker block hash sync
- MooncakeConnectorScheduler: set_block_pool() to access BlockPool,
build_connector_meta() computes hash table deltas each step,
update_state_after_alloc() captures request block hashes for direct_read
- MooncakeConnectorWorker: _start_direct_read() + _direct_read_single()
implements D-side RDMA read via batch_transfer_sync_read, with
HTTP query/unpin to C's bootstrap server
Bootstrap server (mooncake_utils.py):
- POST /query_blocks: look up block hashes, return block_ids + GPU layout
- POST /unpin_blocks: release pin tracking
- set_worker_kv_info(): register GPU addresses at init
- update_hash_table(): receive scheduler deltas each step
Scheduler (scheduler.py):
- One-line hookup: pass block_pool to connector after KVCacheManager init
Proxy (cache_aware_proxy.py):
- _handle_direct_read_offload: sends request ONLY to D with
direct_read=True + remote_bootstrap_addr. No request to C at all.
- C's scheduler is completely uninvolved (0 GPU time on C)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
vLLM Mooncake patch:
- get_num_new_matched_tokens: support remote_num_tokens parameter for
partial remote prefill (pull N tokens from remote, compute rest locally)
- update_state_after_alloc: only allocate receive blocks for external portion
Proxy _handle_heavy_offload rewrite:
- Step 1: C_s exports ONLY cached blocks (truncated prompt, 0 compute)
- Step 2: D pulls cached blocks + does local prefill for new tokens + decodes
- C_s's blocks auto-freed by Mooncake delay_free after D confirms receipt
This enables true session migration: C_s releases cache, D takes over.
C_s's GPU is freed immediately (no compute), vs old approach where C_s
had to do full prefill (1-15s GPU occupancy).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
third_party/vllm/ now tracked in git for direct patch management.
Based on vLLM v0.18.1 release with one patch applied:
vllm/v1/core/sched/scheduler.py:
Replace fatal assert with graceful skip when KV transfer callback
arrives for an already-aborted request during PD disaggregated serving.
Future vLLM modifications should be made directly in third_party/vllm/
and committed normally. The patches/ directory is kept as documentation
of what changed from upstream.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
