Set PYTHONHASHSEED=42 for elastic mode to ensure consistent block hashes

Root cause confirmed: NONE_HASH = os.urandom(32) differs between
scheduler and bootstrap server even in the same process (init_none_hash
called separately by each import path). PYTHONHASHSEED makes it
deterministic: NONE_HASH = hash_fn(seed), same across all code paths.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/bench.sh

@@ -133,6 +133,7 @@ launch_instances() {
         local logfile="$OUTDIR/vllm_inst_${i}.log"
 
         if [ "$MODE" = "elastic" ]; then
+            PYTHONHASHSEED=42 \
             VLLM_MOONCAKE_BOOTSTRAP_PORT=$((8998 + i)) \
             MASTER_PORT=$master \
             CUDA_VISIBLE_DEVICES=$i \

third_party/vllm/vllm/distributed/kv_transfer/kv_connector/v1/mooncake/mooncake_utils.py

@@ -252,11 +252,17 @@ class MooncakeBootstrapServer:
             prev_hash = block_hash
 
             bid = self._hash_table.get(block_hash.hex())
+            if i == 0:
+                table_sample = next(iter(self._hash_table)) if self._hash_table else "empty"
+                logger.info(
+                    "_lookup_by_tokens: block0 hash=%s, NONE_HASH=%s, table_sample=%s",
+                    block_hash.hex()[:16], NONE_HASH.hex()[:16], table_sample[:16])
             if bid is not None:
                 block_ids.append(bid)
                 pinned_ids.append(bid)
             else:
-                block_ids.append(None)
+                if i == 0:
+                    block_ids.append(None)
                 break
 
         return block_ids, pinned_ids