public static ReplyProcessor21 send(InternalDistributedMember primary, PartitionedRegion p,
      int bucketId) {
    ReplyProcessor21 reply = new ReplyProcessor21(p.getDistributionManager(), primary);
    FlushMessage fm = new FlushMessage(p.getPRId(), bucketId, reply.getProcessorId(), primary);
    p.getDistributionManager().putOutgoing(fm);
    return reply;
  }
Send this message to the bucket primary, after the
{@link ReplyProcessor21#waitForRepliesUninterruptibly()} returns, all updates from the primary
should be complete. Use this from a host of a backup bucket (aka secondary) when the update
operations originating from the primary {@link Scope#DISTRIBUTED_NO_ACK do not require an
acknowldgement}

@return a processor on which to wait for the flush operation to complete
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/FlushMessage.java