public BucketLock getBucketLock(int bucketID) {
    String lockName = getLockNameForBucket2NodeModification(bucketID);
    return new BucketLock(lockName, getCache(), false);
  }
Ask the grantor who has the lock

@return the ID of the member holding the lock
geode-core/src/main/java/org/apache/geode/internal/cache/PartitionedRegion.java