[Bug]: KV events subscriber expecting `BlockHash` but receives `ExternalBlockHash`

[atalhens]

Your current environment

The output of python collect_env.py

Your output of `python collect_env.py` here

🐛 Describe the bug

KV events subscriber expecting BlockHash but receives ExternalBlockHash

The current kv_event_subscriber.py [https://github.com/vllm-project/vllm/blob/main/examples/online_serving/kv_events_subscriber.py](url) is listening to KV block events as ExternalBlockHash, but the current implementation assumes it to be of the latter type, hence causing this error.

Current BlockHash used references byte type, and this causes a decoding error.

from vllm.v1.core.kv_cache_utils import BlockHash

I did explore the codebase for changes that would lead to the optimal and feasible solution. I believe changing the current subscriber to ExternalBlockHash seems like a well-lit path, considering that it would be backward compatible with the previous type.

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[heheda12345]

fixed by #26265