MySQL 8 复制（二）——半同步复制

select name, type, processlist_state from performance_schema.threads where name like '%ack_receiver%';
+------------------------------+------------+--------------------------------------+
| name                         | type       | processlist_state                    |
+------------------------------+------------+--------------------------------------+
| thread/semisync/Ack_receiver | BACKGROUND | Waiting for semi-sync ACK from slave |
+------------------------------+------------+--------------------------------------+

semi-sync master failed on net_flush() before waiting for slave reply.

plugin/semisync/semisync_master.cc
403 /*******************************************************************************
404  *
405  * <ReplSemiSyncMaster> class: the basic code layer for sync-replication master.
406  * <ReplSemiSyncSlave>  class: the basic code layer for sync-replication slave.
407  *
408  * The most important functions during semi-syn replication listed:
409  *
410  * Master:
          //实际由Ack_receiver线程调用，处理semi-sync复制状态，获取备库最新binlog位点，唤醒对应线程
411  *  . reportReplyBinlog():  called by the binlog dump thread when it receives
412  *                          the slave's status information.
          //根据semi-sync运行状态设置数据包头semi-sync标记
413  *  . updateSyncHeader():   based on transaction waiting information, decide
414  *                          whether to request the slave to reply.
          //存储当前binlog 文件名和偏移量，更新当前最大的事务 binlog 位置
415  *  . writeTranxInBinlog(): called by the transaction thread when it finishes
416  *                          writing all transaction events in binlog.
          //实现客户端同步等待逻辑
417  *  . commitTrx():          transaction thread wait for the slave reply.
418  *
419  * Slave:
          //确认网络包头是否有semi-sync标记
420  *  . slaveReadSyncHeader(): read the semi-sync header from the master, get the
421  *                           sync status and get the payload for events.
          //给Master发送ACK报文
422  *  . slaveReply():          reply to the master about the replication progress.
423  *
424  ******************************************************************************/

Ack_receiver线程，不断遍历slave，通过select监听slave网络包，处理semi-sync复制状态，唤醒等待线程。
plugin/semisync/semisync_master_ack_receiver.cc Ack_receiver::run()
->plugin/semisync/semisync_master.cc ReplSemiSyncMaster::reportReplyPacket
  ->plugin/semisync/semisync_master.cc ReplSemiSyncMaster::reportReplyBinlog

binlog Dump线程。如果slave是semi-slave，通过add_slave将slave添加到监听队列，在发送网络包时根据semi-sync运行状态设置包头的semi-sync标记。
sql/rpl_binlog_sender.cc Binlog_sender::run()
->sql/rpl_binlog_sender.cc Binlog_sender::send_binlog
  ->sql/rpl_binlog_sender.cc Binlog_sender::send_events
    ->sql/rpl_binlog_sender.cc Binlog_sender::before_send_hook
      ->plugin/semisync/semisync_master_plugin.cc repl_semi_before_send_event
        ->plugin/semisync/semisync_master.cc ReplSemiSyncMaster::updateSyncHeader

事务提交阶段，在flush binlog后，存储当前binlog 文件名和偏移量，更新当前最大的事务 binlog 位置。
sql/binlog.cc MYSQL_BIN_LOG::ordered_commit
 ->plugin/semisync/semisync_master_plugin.cc repl_semi_report_binlog_update//after_flush
   ->plugin/semisync/semisync_master.cc repl_semisync.writeTranxInBinlog

事务提交阶段，客户端等待处理逻辑，分为after_sync和after_commit两种情况
sql/binlog.cc MYSQL_BIN_LOG::ordered_commit
  ->sql/binlog.cc process_after_commit_stage_queue || call_after_sync_hook
    ->plugin/semisync/semisync_master_plugin.cc repl_semi_report_commit || repl_semi_report_binlog_sync
      ->plugin/semisync/semisync_master.cc ReplSemiSyncMaster::commitTrx

Slave IO线程，读取数据后后检查包头是否有semi-sync标记。
sql/rpl_slave.cc handle_slave_io
  ->plugin/semisync/semisync_slave_plugin.cc repl_semi_slave_read_event
    ->plugin/semisync/semisync_slave.cc ReplSemiSyncSlave::slaveReadSyncHeader

Slave IO线程，在queue event后，在需要回复Master ACK报文的时候，回复Master ACK报文。
sql/rpl_slave.cc handle_slave_io
  ->plugin/semisync/semisync_slave_plugin.cc repl_semi_slave_queue_event
    ->plugin/semisync/semisync_slave.cc ReplSemiSyncSlave::slaveReply

plugin/semisync/semisync_master_plugin.cc

68 int repl_semi_report_binlog_sync(Binlog_storage_param *param,
69                                  const char *log_file,
70                                  my_off_t log_pos)
71 {
72   if (rpl_semi_sync_master_wait_point == WAIT_AFTER_SYNC)
73     return repl_semisync.commitTrx(log_file, log_pos);
74   return 0;
75 }

97 int repl_semi_report_commit(Trans_param *param)
   ...
102   if (rpl_semi_sync_master_wait_point == WAIT_AFTER_COMMIT &&
106     return repl_semisync.commitTrx(binlog_name, param->log_pos);

sql/binlog.cc ordered_commit
       //当sync_period(sync_binlog)为1时，在sync之后update binlog end pos
9002   update_binlog_end_pos_after_sync= (get_sync_period() == 1);
       ...
9021     if (!update_binlog_end_pos_after_sync)
           //更新binlog end position,dump线程会发送更新后的events
9022       update_binlog_end_pos();
       ...
         //
9057     std::pair<bool, bool> result= sync_binlog_file(false);
       ...
9061   if (update_binlog_end_pos_after_sync)
9062   {
       ...
9068       update_binlog_end_pos(tmp_thd->get_trans_pos());
9069   }

sql/binlog.cc sync_binlog_file
8618 std::pair<bool, bool>
8619 MYSQL_BIN_LOG::sync_binlog_file(bool force)
8620 {
8621   bool synced= false;
8622   unsigned int sync_period= get_sync_period();//sync_binlog值
       //sync_period为0不做sync操作，其他值为达到sync调用次数后sync
8623   if (force || (sync_period && ++sync_counter >= sync_period))
8624   {

sql/rpl_slave.cc handle_slave_io

5764       if (queue_event(mi, event_buf, event_len))
           ...
5771       if (RUN_HOOK(binlog_relay_io, after_queue_event,
5772                    (thd, mi, event_buf, event_len, synced)))

after_queue_event
->plugin/semisync/semisync_slave_plugin.cc repl_semi_slave_queue_event
->plugin/semisync/semisync_slave.cc ReplSemiSyncSlave::slaveReply

queue_event
->sql/binlog.cc MYSQL_BIN_LOG::append_buffer(const char* buf, uint len, Master_info *mi)
->sql/binlog.cc after_append_to_relay_log(mi);
->sql/binlog.cc flush_and_sync(0)
->sql/binlog.cc sync_binlog_file(force)

-- 在主
install plugin rpl_semi_sync_master soname 'semisync_master.so';

-- 在每个从
install plugin rpl_semi_sync_slave soname 'semisync_slave.so';

mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
ERROR 1126 (HY000): Can't open shared library
'/usr/local/mysql/lib/plugin/semisync_master.so'
(errno: 22 libimf.so: cannot open shared object file:
No such file or directory)

mysql> select plugin_name, plugin_status
    ->   from information_schema.plugins
    ->  where plugin_name like '%semi%';
+----------------------+---------------+
| plugin_name          | plugin_status |
+----------------------+---------------+
| rpl_semi_sync_master | ACTIVE        |
+----------------------+---------------+
1 row in set (0.00 sec)

-- 主
mysql> show variables like '%semi%';
+-------------------------------------------+------------+
| Variable_name                             | Value      |
+-------------------------------------------+------------+
| rpl_semi_sync_master_enabled              | OFF        |
| rpl_semi_sync_master_timeout              | 10000      |
| rpl_semi_sync_master_trace_level          | 32         |
| rpl_semi_sync_master_wait_for_slave_count | 1          |
| rpl_semi_sync_master_wait_no_slave        | ON         |
| rpl_semi_sync_master_wait_point           | AFTER_SYNC |
+-------------------------------------------+------------+
6 rows in set (0.00 sec)

--从
mysql> show variables like '%semi%';
+---------------------------------+-------+
| Variable_name                   | Value |
+---------------------------------+-------+
| rpl_semi_sync_slave_enabled     | OFF   |
| rpl_semi_sync_slave_trace_level | 32    |
+---------------------------------+-------+
2 rows in set (0.00 sec)

-- 主
set global rpl_semi_sync_master_enabled = 1;

-- 从
set global rpl_semi_sync_slave_enabled = 1;

# 主
plugin-load="rpl_semi_sync_master=semisync_master.so"
rpl_semi_sync_master_enabled=1

# 从
plugin-load="rpl_semi_sync_slave=semisync_slave.so"
rpl_semi_sync_slave_enabled=1

plugin-load = "rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so"
rpl-semi-sync-master-enabled = 1
rpl-semi-sync-slave-enabled = 1

mysql> stop slave io_thread;
mysql> start slave io_thread;

-- 主
mysql> show status like 'Rpl_semi_sync_master_status';
+-----------------------------+-------+
| Variable_name               | Value |
+-----------------------------+-------+
| Rpl_semi_sync_master_status | ON    |
+-----------------------------+-------+
1 row in set (0.01 sec)

-- 从
mysql> show status like 'Rpl_semi_sync_slave_status';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Rpl_semi_sync_slave_status | ON    |
+----------------------------+-------+
1 row in set (0.00 sec)

-- 主
mysql> show status like 'rpl_semi_sync%';
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 2     |
| Rpl_semi_sync_master_net_avg_wait_time     | 0     |
| Rpl_semi_sync_master_net_wait_time         | 0     |
| Rpl_semi_sync_master_net_waits             | 0     |
| Rpl_semi_sync_master_no_times              | 0     |
| Rpl_semi_sync_master_no_tx                 | 0     |
| Rpl_semi_sync_master_status                | ON    |
| Rpl_semi_sync_master_timefunc_failures     | 0     |
| Rpl_semi_sync_master_tx_avg_wait_time      | 0     |
| Rpl_semi_sync_master_tx_wait_time          | 0     |
| Rpl_semi_sync_master_tx_waits              | 0     |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0     |
| Rpl_semi_sync_master_wait_sessions         | 0     |
| Rpl_semi_sync_master_yes_tx                | 0     |
+--------------------------------------------+-------+
14 rows in set (0.00 sec)

-- 从
mysql> show status like 'rpl_semi_sync%';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Rpl_semi_sync_slave_status | ON    |
+----------------------------+-------+
1 row in set (0.01 sec)

-- 主
mysql> create database test;
Query OK, 1 row affected (0.00 sec)

mysql> use test;
Database changed
mysql> create table test.t1 (a int) engine=innodb;
Query OK, 0 rows affected (0.02 sec)

mysql> insert into t1 values(1);
Query OK, 1 row affected (0.02 sec)

mysql> show status like 'rpl_semi_sync%';
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 2     |
| Rpl_semi_sync_master_net_avg_wait_time     | 0     |
| Rpl_semi_sync_master_net_wait_time         | 0     |
| Rpl_semi_sync_master_net_waits             | 6     |
| Rpl_semi_sync_master_no_times              | 0     |
| Rpl_semi_sync_master_no_tx                 | 0     |
| Rpl_semi_sync_master_status                | ON    |
| Rpl_semi_sync_master_timefunc_failures     | 0     |
| Rpl_semi_sync_master_tx_avg_wait_time      | 758   |
| Rpl_semi_sync_master_tx_wait_time          | 2274  |
| Rpl_semi_sync_master_tx_waits              | 3     |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0     |
| Rpl_semi_sync_master_wait_sessions         | 0     |
| Rpl_semi_sync_master_yes_tx                | 3     |
+--------------------------------------------+-------+
14 rows in set (0.00 sec)

mysql>

-- 从
mysql> select * from test.t1;
+------+
| a    |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

-- 主
mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | OFF   |
+---------------+-------+
1 row in set (0.01 sec)

mysql> set session autocommit=0;                  -- 关闭自动提交，开启事务
Query OK, 0 rows affected (0.00 sec)

mysql> insert into t1 values(2);                  -- 向事务表插入记录
Query OK, 1 row affected (0.00 sec)

mysql> create table t2 (a int) engine=myisam;     -- 执行一个DDL语句，创建非事务表t2
Query OK, 0 rows affected (0.01 sec)

mysql> insert into t1 values(3);                  -- 向事务表插入记录
Query OK, 1 row affected (0.00 sec)

mysql> insert into t2 values(3);                  -- 向非事务表插入记录
Query OK, 1 row affected (0.01 sec)

mysql> rollback;                                  -- 回滚事务
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+---------------------------------------------------------------+
| Level   | Code | Message                                                       |
+---------+------+---------------------------------------------------------------+
| Warning | 1196 | Some non-transactional changed tables couldn't be rolled back |
+---------+------+---------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select * from t1;
+------+
| a    |
+------+
|    1 |
|    2 |
+------+
2 rows in set (0.00 sec)

mysql> select * from t2;
+------+
| a    |
+------+
|    3 |
+------+
1 row in set (0.00 sec)

mysql> show status like 'rpl_semi_sync%';
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 2     |
| Rpl_semi_sync_master_net_avg_wait_time     | 0     |
| Rpl_semi_sync_master_net_wait_time         | 0     |
| Rpl_semi_sync_master_net_waits             | 12    |
| Rpl_semi_sync_master_no_times              | 0     |
| Rpl_semi_sync_master_no_tx                 | 0     |
| Rpl_semi_sync_master_status                | ON    |
| Rpl_semi_sync_master_timefunc_failures     | 0     |
| Rpl_semi_sync_master_tx_avg_wait_time      | 691   |
| Rpl_semi_sync_master_tx_wait_time          | 4149  |
| Rpl_semi_sync_master_tx_waits              | 6     |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0     |
| Rpl_semi_sync_master_wait_sessions         | 0     |
| Rpl_semi_sync_master_yes_tx                | 6     |
+--------------------------------------------+-------+
14 rows in set (0.00 sec)

mysql> 

-- 从
mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | ON    |
+---------------+-------+
1 row in set (0.01 sec)

mysql> melect * from test.t1;
+------+
| a    |
+------+
|    1 |
|    2 |
+------+
2 rows in set (0.00 sec)

mysql> select * from test.t2;
+------+
| a    |
+------+
|    3 |
+------+
1 row in set (0.01 sec)

mysql>

-- 关闭两个从库的复制
mysql> stop slave;
Query OK, 0 rows affected (0.01 sec)

mysql> show status like 'rpl_semi_sync%';                -- 查看当前是否启用半同步复制
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Rpl_semi_sync_slave_status | OFF   |
+----------------------------+-------+
1 row in set (0.00 sec)

mysql>

-- 主
mysql> show status like 'Rpl_semi_sync_master_clients';  -- 查看当前半同步从库数
+------------------------------+-------+
| Variable_name                | Value |
+------------------------------+-------+
| Rpl_semi_sync_master_clients | 0     |
+------------------------------+-------+
1 row in set (0.00 sec)

mysql> show status like 'Rpl_semi_sync_master_status';   -- 查看当前是否启用半同步复制
+-----------------------------+-------+
| Variable_name               | Value |
+-----------------------------+-------+
| Rpl_semi_sync_master_status | ON    |
+-----------------------------+-------+
1 row in set (0.00 sec)

mysql> insert into t1 values(3);
Query OK, 1 row affected (0.00 sec)

mysql> commit;
Query OK, 0 rows affected (10.00 sec)

mysql> select * from t1;
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
+------+
3 rows in set (0.00 sec)

mysql> show status like 'Rpl_semi_sync_master_status';
+-----------------------------+-------+
| Variable_name               | Value |
+-----------------------------+-------+
| Rpl_semi_sync_master_status | OFF   |
+-----------------------------+-------+
1 row in set (0.01 sec)

mysql>

-- 启动一个从库的复制
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test.t1;
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
+------+
3 rows in set (0.00 sec)

mysql> show status like 'rpl_semi_sync%';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Rpl_semi_sync_slave_status | ON    |
+----------------------------+-------+
1 row in set (0.01 sec)

mysql>

-- 主
mysql> show variables like 'rpl_semi_sync_master_wait_for_slave_count';
+-------------------------------------------+-------+
| Variable_name                             | Value |
+-------------------------------------------+-------+
| rpl_semi_sync_master_wait_for_slave_count | 1     |
+-------------------------------------------+-------+
1 row in set (0.00 sec)

mysql> show status like 'Rpl_semi_sync_master_clients';
+------------------------------+-------+
| Variable_name                | Value |
+------------------------------+-------+
| Rpl_semi_sync_master_clients | 1     |
+------------------------------+-------+
1 row in set (0.00 sec)

mysql> show status like 'Rpl_semi_sync_master_status';
+-----------------------------+-------+
| Variable_name               | Value |
+-----------------------------+-------+
| Rpl_semi_sync_master_status | ON    |
+-----------------------------+-------+
1 row in set (0.00 sec)

mysql> insert into t1 values(4);
Query OK, 1 row affected (0.00 sec)

mysql> commit;
Query OK, 0 rows affected (0.01 sec)

mysql> 

-- 从
mysql> select * from test.t1;
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
+------+
4 rows in set (0.00 sec)

mysql> 

-- 关闭rpl_semi_sync_master_wait_no_slave
mysql> set global rpl_semi_sync_master_wait_no_slave=off;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'rpl_semi_sync_master_wait_no_slave';
+------------------------------------+-------+
| Variable_name                      | Value |
+------------------------------------+-------+
| rpl_semi_sync_master_wait_no_slave | OFF   |
+------------------------------------+-------+
1 row in set (0.00 sec)

mysql> 

-- 关闭所有从库的复制
mysql> stop slave;
Query OK, 0 rows affected (0.01 sec)

mysql> 

-- 主
mysql> show status like 'Rpl_semi_sync_master_clients';  -- 查看当前半同步从库数
+------------------------------+-------+
| Variable_name                | Value |
+------------------------------+-------+
| Rpl_semi_sync_master_clients | 0     |
+------------------------------+-------+
1 row in set (0.00 sec)

mysql> show status like 'Rpl_semi_sync_master_clients';
+------------------------------+-------+
| Variable_name                | Value |
+------------------------------+-------+
| Rpl_semi_sync_master_clients | 0     |
+------------------------------+-------+
1 row in set (0.00 sec)

mysql> show status like 'Rpl_semi_sync_master_status';
+-----------------------------+-------+
| Variable_name               | Value |
+-----------------------------+-------+
| Rpl_semi_sync_master_status | OFF   |
+-----------------------------+-------+
1 row in set (0.00 sec)

mysql> insert into t1 values(5);
Query OK, 1 row affected (0.00 sec)

mysql> commit;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from t1;
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
+------+
5 rows in set (0.00 sec)

mysql>