Mysql 5.7中mysql.gtid_executed表及其他变量更改时机是什么

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一、主库修改时机

(2) binlog打开

• mysql.gtid_executed表修改时机

在binlog发生切换(rotate)的时候保存直到上一个binlog文件执行过的全部Gtid，它不是实时更新的。
栈帧如下:

#0  Gtid_table_persistor::save (this=0x2f9f9c0, gtid_set=0x7ffff03595a0) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_persist.cc:425#1  0x0000000001803dbe in Gtid_state::save (this=0x2ff8bb0, gtid_set=0x7ffff03595a0) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:796#2  0x0000000001803f62 in Gtid_state::save_gtids_of_last_binlog_into_table (this=0x2ff8bb0, on_rotation=true)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:835#3  0x000000000185266d in MYSQL_BIN_LOG::new_file_impl (this=0x2dffc80, need_lock_log=false, extra_description_event=0x0)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:6751#4  0x00000000018520a7 in MYSQL_BIN_LOG::new_file_without_locking (this=0x2dffc80, extra_description_event=0x0)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:6636#5  0x0000000001853e67 in MYSQL_BIN_LOG::rotate (this=0x2dffc80, force_rotate=true, check_purge=0x7ffff0359c4b)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:7292

其主要逻辑在Gtid_state::save_gtids_of_last_binlog_into_table 中我们在随后的部分讨论这个函数逻辑。

• gtid_executed变量修改时机

如前文所述ordered_commit flush阶段生成Gtid，在commit阶段才计入gtid_executed变量，它是实时更新的。
栈帧如下：

#0  Gtid_set::_add_gtid (this=0x2ff8d38, sidno=1, gno=16) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid.h:1135#1  0x0000000001804576 in Gtid_set::_add_gtid (this=0x2ff8d38, gtid=...) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid.h:1166#2  0x00000000018024ba in Gtid_state::update_gtids_impl (this=0x2ff8bb0, thd=0x7fff2c000b70, is_commit=true)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:304#3  0x00000000018020df in Gtid_state::update_on_commit (this=0x2ff8bb0, thd=0x7fff2c000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:148#4  0x00000000018573d4 in MYSQL_BIN_LOG::process_commit_stage_queue (this=0x2dffc80, thd=0x7fff2c000b70, first=0x7fff2c000b70)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:8646#5  0x0000000001858b51 in MYSQL_BIN_LOG::ordered_commit (this=0x2dffc80, thd=0x7fff2c000b70, all=false, skip_commit=false)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:9304

其主要逻辑在Gtid_state::update_gtids_impl中我们在随后的部分讨论这个函数逻辑。

• gtid_purged变量修改时机

在Mysql触发的清理binlog的情况下，比如purge binary logs to或者超过参数expire_logs_days设置的天数后自动删除，需要将丢失的Gtid计入这个变量中。
栈帧如下:

#0  MYSQL_BIN_LOG::init_gtid_sets (this=0x2e00280, all_gtids=0x0, lost_gtids=0x2fcaee8, verify_checksum=false, need_lock=false, trx_parser=0x0, gtid_partial_trx=0x0, is_server_starting=false)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:4333#1  0x0000000001850b8e in MYSQL_BIN_LOG::purge_logs (this=0x2e00280, to_log=0x7fff57a74ad0 "/root/mysql5.7.14/percona-server-5.7.14-7/mysql-test/var/mysqld.1/test.000202", included=false, need_lock_index=true,     need_update_threads=true, decrease_log_space=0x0, auto_purge=false) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:6036#2  0x0000000001848ecf in purge_master_logs (thd=0x7fff49200dc0, to_log=0x7fff492051a8 "test.000202") at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:2815

其主要逻辑在MYSQL_BIN_LOG::purge_logs中，我们随后查看其代码片段，同时MYSQL_BIN_LOG::init_gtid_sets函数是一个及其重要的函数，主要用在：

• Mysql启动时候初始化整个Gtid_state中的各种Gtid_set。

• Mysql删除binlog(如purge binary logfiles或者超过expire_logs_days设置)后需要确认gtid_purged变量(及Gtid_state.lost_gtids)的值的时候。

随后我会单独一节来讲解Mysql Gtid模块的初始化还会讲解这个函数。

二、主库修改时机源码函数分析

这里就对上面提到的主要逻辑函数进行分析

• Gtid_state::save_gtids_of_last_binlog_into_table函数逻辑

logged_gtids_last_binlog.add_interval_memory(PREALLOCATED_INTERVAL_COUNT, iv); //这里构建一个logged_gtids_last_binlog集合来保存切换后需要写入表和previous_gtids_logged的Gtid  /*    logged_gtids_last_binlog= executed_gtids - previous_gtids_logged -                              gtids_only_in_table  */  global_sid_lock->wrlock();//  ret= (logged_gtids_last_binlog.add_gtid_set(&executed_gtids) !=  //将当前执行过的Gtid全部加入logged_gtids_last_binlog 列如:executed_gtids start=1, end=27         RETURN_STATUS_OK);  if (!ret)  {    logged_gtids_last_binlog.remove_gtid_set(&previous_gtids_logged); //获得上一个binlog文件包含的全部Gtid，并且做一个差集 列如:previous_gtids_logged 为start=1, end=25                                                                      //做完差集后logged_gtids_last_binlog为start=26, end=27    logged_gtids_last_binlog.remove_gtid_set(>ids_only_in_table);//此处主库一定为空，除非异常情况    if (!logged_gtids_last_binlog.is_empty())     {      /* Prepare previous_gtids_logged for next binlog on binlog rotation */      if (on_rotation)        ret= previous_gtids_logged.add_gtid_set(&logged_gtids_last_binlog);//将这个start=26, end=27的Gtid集合加入到previous_gtids_logged中，这样previous_gtids_logged也完整了      global_sid_lock->unlock();      /* Save set of GTIDs of the last binlog into gtid_executed table */      if (!ret)        ret= save(&logged_gtids_last_binlog);//将这个start=26, end=27的Gtid集合写入到表mysql.gtid_executed表中    }

• Gtid_state::update_gtids_impl函数代码片段

while (g.sidno != 0)    {      if (g.sidno != prev_sidno)        sid_locks.lock(g.sidno);      owned_gtids.remove_gtid(g); //从owned_gtid中去掉      git.next();      g= git.get();      if (is_commit)        executed_gtids._add_gtid(g);//将这个Gtid加入到executed_gtids    }

• MYSQL_BIN_LOG::purge_logs函数代码片段

if (!is_relay_log)  {    global_sid_lock->wrlock();    error= init_gtid_sets(NULL,                          const_cast(gtid_state->get_lost_gtids()),                          opt_master_verify_checksum,                          false/*false=don't need lock*/,                          NULL/*trx_parser*/, NULL/*gtid_partial_trx*/);//这里我看到将gtid_state->lost_gtids直接传入给了init_gtid_sets                                                                        //init_gtid_sets会做正向查找获得gtid_state->lost_gtids这个函数稍后                                                                        //详细讨论    global_sid_lock->unlock();    if (error)      goto err;  }

三、从库修改时机

(2)binlog开启同时参数log_slave_updates开启的情况

这种情况sql_thread执行过的Gtid事物可以通过binlog进行维护，所以mysql.gtid_executed表和gtid_purged变量不需要实时更新。

• mysql.gtid_executed表修改时机

和主库一致。及在进行日志切换的时候进行更新，不做讨论

• gtid_executed变量修改时机

和主库一样实时更新，不做讨论

• gtid_purged变量修改时机

和主库一致，binlog删除时更新，不做讨论

四、从库修改时机源码函数分析

• commit_owned_gtids函数逻辑：

//如果 binlog 没有开启包括(log_bin=0 和 sql_log_bin =0 )或者 开启了binlog 但是slave线程并且slave update 没有开启,都会记录gtid到表//但是这里要注意一点在主库上如果binlog不开启那么thd->owned_gtid.sidno ==0 因为这个时候Gtid都没有生成,生成阶段为order_commit的commit阶段  if ((!opt_bin_log || (thd->slave_thread && !opt_log_slave_updates)) &&       (all || !thd->in_multi_stmt_transaction_mode()) && //all 代表是否是显示begin 事物 in_multi_stmt_transaction_mode则相反      !thd->is_operating_gtid_table_implicitly && //是否是GTID_NEXT方式 flase      !thd->is_operating_substatement_implicitly)//是否是子语句 flase  {    /*      If the binary log is disabled for this thread (either by      log_bin=0 or sql_log_bin=0 or by log_slave_updates=0 for a      slave thread), then the statement will not be written to      the binary log. In this case, we should save its GTID into      mysql.gtid_executed table and @@GLOBAL.GTID_EXECUTED as it      did when binlog is enabled.    */    if (thd->owned_gtid.sidno > 0)    {      error= gtid_state->save(thd);//就是这里进行了mysql.gtid_executed表的实时更新      *need_clear_owned_gtid_ptr= true;    }    else if (thd->owned_gtid.sidno == THD::OWNED_SIDNO_ANONYMOUS)      *need_clear_owned_gtid_ptr= true;  }

• Gtid_state::update_gtids_impl_own_gtid 函数逻辑片段
  这个函数是5.7.17的，5.7.14没有逻辑放到了Gtid_state::update_gtids_impl中

if (is_commit)  {    DBUG_EXECUTE_IF(      "rpl_gtid_update_on_commit_simulate_out_of_memory",      DBUG_SET("+d,rpl_gtid_get_free_interval_simulate_out_of_memory"););    /*      Any session adds transaction owned GTID into global executed_gtids.      If binlog is disabled, we report @@GLOBAL.GTID_PURGED from      executed_gtids, since @@GLOBAL.GTID_PURGED and @@GLOBAL.GTID_EXECUTED      are always same, so we did not save gtid into lost_gtids for every      transaction for improving performance.      If binlog is enabled and log_slave_updates is disabled, slave      SQL thread or slave worker thread adds transaction owned GTID      into global executed_gtids, lost_gtids and gtids_only_in_table.    */    executed_gtids._add_gtid(thd->owned_gtid); //加入executed_gtids集合    thd->rpl_thd_ctx.session_gtids_ctx().      notify_after_gtid_executed_update(thd);    if (thd->slave_thread && opt_bin_log && !opt_log_slave_updates)//如果是slave线程同时binlog开启了并且log_slave_updates关闭了                                                                   //如果binlog关闭则使用 executed_gtids这样提高性能前面的注释说了    {      lost_gtids._add_gtid(thd->owned_gtid);  //写入lost_gtids也就是更新参数gtid_purged变量      gtids_only_in_table._add_gtid(thd->owned_gtid);    }  }

五、通用更改时机

mysql.gtid_executed表修改时机

• 在reset master的时候清空本表
  栈帧如下：

#0  Gtid_table_persistor::delete_all (this=0x2f9f9c0, table=0x7fff2c0116a0) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_persist.cc:795#1  0x000000000180a4ef in Gtid_table_persistor::reset (this=0x2f9f9c0, thd=0x7fff2c000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_persist.cc:689#2  0x0000000001801f2e in Gtid_state::clear (this=0x2ff8bb0, thd=0x7fff2c000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:36#3  0x000000000184fee6 in MYSQL_BIN_LOG::reset_logs (this=0x2dffe80, thd=0x7fff2c000b70, delete_only=false)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:5586#4  0x0000000001872308 in reset_master (thd=0x7fff2c000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_master.cc:587

其主要逻辑在Gtid_state::clear中。

• 在set global gitd_purged的时候，设置本表
  栈帧如下：

#0  Gtid_table_persistor::save (this=0x2f9f9c0, gtid_set=0x7ffff0359a70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_persist.cc:425#1  0x000000000180400a in Gtid_state::save (this=0x2ff8bb0, gtid_set=0x7ffff0359a70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:796#2  0x0000000001803c25 in Gtid_state::add_lost_gtids (this=0x2ff8bb0, gtid_set=0x7ffff0359a70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_gtid_state.cc:737#3  0x00000000016778f3 in Sys_var_gtid_purged::global_update (this=0x2de9fe0, thd=0x7fff2c000b70, var=0x7fff2c006630)    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sys_vars.cc:5888#4  0x00000000014d5cd1 in sys_var::update (this=0x2de9fe0, thd=0x7fff2c000b70, var=0x7fff2c006630) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/set_var.cc:184#5  0x00000000014d74ee in set_var::update (this=0x7fff2c006630, thd=0x7fff2c000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/set_var.cc:812#6  0x00000000014d6d1a in sql_set_variables (thd=0x7fff2c000b70, var_list=0x7fff2c003528) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/set_var.cc:669

其主要逻辑在Gtid_state::add_lost_gtids中。

gtid_executed变量修改时机

• 在reset master的时候清空本变量
  栈帧同上

• 在set global gitd_purged的时候，设置本变量
  栈帧同上

• 在mysql启动的时候初始化设置gtid_executed变量，这个将在后面章节详细描述描述步骤。

gtid_purged变量修改时机

• 在reset master的时候清空本变量
  栈帧同上

• 在set global gitd_purged的时候，设置本变量
  栈帧同上

• 在mysql启动的时候初始化设置gtid_executed变量，这个将在后面章节详细描述描述步骤。

六、通用更改时机源码函数分析

• Gtid_state::clear函数逻辑

int Gtid_state::clear(THD *thd){ ....  // the wrlock implies that no other thread can hold any of the mutexes  sid_lock->assert_some_wrlock();  lost_gtids.clear();//此处清空gtid_purged变量  executed_gtids.clear();//此处清空gtid_executed变量  gtids_only_in_table.clear();//清空only in table Gtid set  previous_gtids_logged.clear();//清空 previous gtids logged Gtid set  /* Reset gtid_executed table. */  if ((ret= gtid_table_persistor->reset(thd)) == 1)//此处清空mysql.gtid_executed表  {    /*      Gtid table is not ready to be used, so failed to      open it. Ignore the error.    */    thd->clear_error();    ret= 0;  }  next_free_gno= 1;  DBUG_RETURN(ret);}

• Gtid_state::add_lost_gtids函数逻辑

enum_return_status Gtid_state::add_lost_gtids(const Gtid_set *gtid_set){  ......  if (save(gtid_set)) //此处将set gtid_purge的值加入到mysql.gtid_executed表中    RETURN_REPORTED_ERROR;  PROPAGATE_REPORTED_ERROR(gtids_only_in_table.add_gtid_set(gtid_set));  PROPAGATE_REPORTED_ERROR(lost_gtids.add_gtid_set(gtid_set));//此处将set gtid_purge的值加入到gtid_purge变量中  PROPAGATE_REPORTED_ERROR(executed_gtids.add_gtid_set(gtid_set));//此处将set gtid_purge的值加入到gtid_executed变量中  lock_sidnos(gtid_set);  broadcast_sidnos(gtid_set);  unlock_sidnos(gtid_set);  DBUG_RETURN(RETURN_STATUS_OK);}

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