Replication进阶(二) 半同步复制-间隔事务提交

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如下场景：

1，
master
gtid_executed uuid：1
gtid_owned uuid:2-3

2，
slave
gtid_executed uuid:1-2
停止从机io thread，uuid:2事务未返回ack
3，
启动从机器 io thread后，会接收主机uuid:3binlog，并且返回此事务的uuid

此时2-3事务在主机上的表现

4，
测试结果为：
2-3事务均提交。

5，
证明ack receiver线上应该判断的是need <= received
代码如下。
控制函数ReplSemiSyncMaster::commitTrx

 while (is_on())
    {
      if (reply_file_name_inited_)
      {
        int cmp = ActiveTranx::compare(reply_file_name_, reply_file_pos_,
                                       trx_wait_binlog_name, trx_wait_binlog_pos);
        if (cmp >= 0)
        {
          /* We have already sent the relevant binlog to the slave: no need to
           * wait here.
           */
          if (trace_level_ & kTraceDetail)
            sql_print_information("%s: Binlog reply is ahead (%s, %lu),",
                                  kWho, reply_file_name_, (unsigned long)reply_file_pos_);
          break;
        }
      }
......
}

compare如下

int ActiveTranx::compare(const char *log_file_name1, my_off_t log_file_pos1,
             const char *log_file_name2, my_off_t log_file_pos2)
{
  int cmp = strcmp(log_file_name1, log_file_name2);

  if (cmp != 0)
    return cmp;

  if (log_file_pos1 > log_file_pos2)
    return 1;
  else if (log_file_pos1 < log_file_pos2)
    return -1;
  return 0;
}

所以实验结果并不意外。