@Override
  public void toData(DataOutput out,
      SerializationContext context) throws IOException {
    super.toData(out, context);
    out.writeInt(bucketId);
    out.writeInt(bucketSize);
  }
This method is called upon receipt and make the desired changes to the PartitionedRegion Note:
It is very important that this message does NOT cause any deadlocks as the sender will wait
indefinitely for the acknowledgement
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/CreateBucketMessage.java