[Bugfix] Fix MultiConnector state corruption in P/D disaggregated con…

[NUABO]

fix #42831
When MultiConnector selects one sub-connector to load KV for a request,
it passes empty blocks (num_external_tokens=0) to all other
sub-connectors. Because the original request (with kv_transfer_params)
was passed to every connector, non-chosen connectors incorrectly started
async KV transfers for requests they did not own.

This led to assertion failures when get_finished() later reported these
requests as done receiving, but their scheduler state no longer matched.

Fix in MultiConnector.update_state_after_alloc(): when a connector was
chosen for this request, pass a shallow-copied request with
kv_transfer_params=None to all other connectors. Their existing
"if not params: return" guard then correctly skips state updates.
When no connector was chosen (producer side, full prefix hit), the
original request is passed through unchanged so producer logic and
remote block freeing still work.

Purpose

Test Plan

Test Result

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[gemini-code-assist]

Code Review

This pull request introduces early returns in the update_state_after_alloc method across the Mooncake, Moriio, and Nixl KV connectors when num_external_tokens is zero. The reviewer identified that these changes break critical functionality for both producers and consumers: they prevent producers from tracking requests or sending KV caches and stop consumers from notifying remote nodes to release memory during full prefix cache hits, which could lead to memory leaks and functional failures.

[gemini-code-assist]

Code Review

This pull request modifies the MultiConnector.update_state_after_alloc method to mask kv_transfer_params for non-chosen connectors, preventing them from incorrectly initiating asynchronous transfers. Feedback indicates that the implementation appears incomplete, as several files mentioned in the PR description are missing from the patch. Additionally, there is a performance concern regarding the use of copy.copy inside a loop, which may introduce significant overhead in the scheduler and should be optimized.

[gemini-code-assist]

Code Review

This pull request updates the update_state_after_alloc method in multi_connector.py to mask kv_transfer_params for connectors not assigned to a request, preventing unintended asynchronous transfers. A review comment suggests simplifying the logic for creating the masked request to improve readability and remove a ternary operator from the loop.

[gemini-code-assist]

Code Review

This pull request updates the update_state_after_alloc method in multi_connector.py to prevent non-chosen connectors from incorrectly initiating asynchronous KV transfers. It introduces a masked request object where kv_transfer_params is set to None, which is then passed to all connectors except the one specifically selected for the request. I have no feedback to provide as there were no review comments.

[Dao007forever]

Thanks for fixing this!