This PR addresses a request ID mismatch issue in the PD
(Prefill-Decoding) separation deployment scenario for vllm-ascend.
Upstream vLLM recently mitigated request ID collisions by appending a
random suffix to each request_id (e.g., req-123 → req-123-abc), refer to
[PR-27987](https://github.com/vllm-project/vllm/pull/27987 ) &
[PR-29665](https://github.com/vllm-project/vllm/pull/29665). While this
works in single-node deployments, it breaks compatibility in
PD-separated setups: the Producer (Prefill node) and Consumer (Decoding
node) end up with different request_id values, preventing the Consumer
from correctly retrieving the KV cache generated by the Producer.
To resolve this, this PR introduces a new field remote_request_id in the
metadata passed via mooncake_connector. The Producer preserves and
forwards the original (unmodified) request_id as remote_request_id. The
Consumer then uses this remote_request_id—instead of its locally
generated suffixed ID—to fetch the correct KV cache from the Prefill
node.
This ensures consistent request identification across PD nodes while
maintaining compatibility with upstream vLLM’s request ID deduplication
mechanism.
<img width="1279" height="781" alt="image"
src="https://github.com/user-attachments/assets/274238c1-dab6-4d3a-9ee4-6e578679b762"
/>
- vLLM version: v0.13.0
- vLLM main:
d68209402d
Signed-off-by: ghphotoframe <854746559@qq.com>
Co-authored-by: jiangweixiang <jwx02384838@antgroup.com>
cef04b3555