ORACLE 中的SHUTDOWN
MySQL SHUTDOWN LEVEL 暂时只有一种，源码中留了 LEVEL 的坑还没填
在此借用 Oracle 的 SHUTDOWN LEVEL 分析
Oracle SHUTDOWN LEVEL 共有四种：ABORT、IMMEDIATE、NORMAL、TRANSACTIONAL
ABORT
- 立即结束所有SQL
- 回滚未提交事务
- 断开所有用户连接
- 下次启动实例时，需要recovery
IMMEDIATE
- 允许正在运行的SQL执行完毕
- 回滚未提交事务
- 断开所有用户连接
NORMAL
- 不允许建立新连接
- 等待当前连接断开
- 下次启动实例时，不需要recovery
TRANSACTIONAL
- 等待事务提交或结束
- 不允许新建连接
- 事务提交或结束后断开连接
MySQL 中的 SHUTDOWN 实际相当于 Oracle 中的 SHUTDOWN IMMEDIATE，重启实例时无需recovery，但回滚事务的过程可能耗时很长
MySQL SHUTDOWN过程分析
- mysql_shutdown 发送SHUTDOWN命令
- dispatch_command() 接受到 COM_SHUTDOWN command，调用kill_mysql()
- kill_mysql()创建 kill_server_thread
- kill_server_thread 调用 kill_server()
- kill_server()
- close_connections()
- 关闭端口
- 断开连接
- 回滚事务（可能耗时很长）
- unireg_end
- clean_up
- innobase_shutdown_for_mysql
- delete_pid_file
- clean_up
- close_connections()
InnoDB shutdown 速度取决于参数 innodb_fast_shutdown
- 0: 最慢，需等待purge完成，change buffer merge完成
- 1: default， 不需要等待purge完成和change buffer merge完成
- 2: 不等待后台删除表完成，row_drop_tables_for_mysql_in_background 不等刷脏页，如果设置了innodb_buffer_pool_dump_at_shutdown，不需要去buffer dump.
case COM_SHUTDOWN: // 接受到SHUTDOWN命令
{
if (packet_length < 1)
{
my_error(ER_MALFORMED_PACKET, MYF(0));
break;
}
status_var_increment(thd->status_var.com_other);
if (check_global_access(thd,SHUTDOWN_ACL)) // 检查权限
break; /* purecov: inspected */
/*
If the client is < 4.1.3, it is going to send us no argument; then
packet_length is 0, packet[0] is the end 0 of the packet. Note that
SHUTDOWN_DEFAULT is 0. If client is >= 4.1.3, the shutdown level is in
packet[0].
*/
enum mysql_enum_shutdown_level level; // 留的坑，default以外的LEVEL都没实现
if (!thd->is_valid_time())
level= SHUTDOWN_DEFAULT;
else
level= (enum mysql_enum_shutdown_level) (uchar) packet[0];
if (level == SHUTDOWN_DEFAULT)
level= SHUTDOWN_WAIT_ALL_BUFFERS; // soon default will be configurable
else if (level != SHUTDOWN_WAIT_ALL_BUFFERS)
{
my_error(ER_NOT_SUPPORTED_YET, MYF(0), "this shutdown level");
break;
}
DBUG_PRINT("quit",("Got shutdown command for level %u", level));
general_log_print(thd, command, NullS); // 记录general_log
my_eof(thd);
kill_mysql(); // 调用kill_mysql()函数，函数内部创建 kill_server_thread 线程
error=TRUE;
break;
}
kill_server() 先调用 close_connections()，再调用 unireg_end()
static void __cdecl kill_server(int sig_ptr)
{
......
close_connections();
if (sig != MYSQL_KILL_SIGNAL &&
sig != 0)
unireg_abort(1); /* purecov: inspected */
else
unireg_end();
结束线程的主要逻辑在 mysqld.cc:close_connections() 中
static void close_connections(void)
......
/* 下面这段代码结束监听端口 */
/* Abort listening to new connections */
DBUG_PRINT("quit",("Closing sockets"));
if (!opt_disable_networking )
{
if (mysql_socket_getfd(base_ip_sock) != INVALID_SOCKET)
{
(void) mysql_socket_shutdown(base_ip_sock, SHUT_RDWR);
(void) mysql_socket_close(base_ip_sock);
base_ip_sock= MYSQL_INVALID_SOCKET;
}
if (mysql_socket_getfd(extra_ip_sock) != INVALID_SOCKET)
{
(void) mysql_socket_shutdown(extra_ip_sock, SHUT_RDWR);
(void) mysql_socket_close(extra_ip_sock);
extra_ip_sock= MYSQL_INVALID_SOCKET;
}
}
......
/* 第一遍遍历线程列表 */
sql_print_information("Giving %d client threads a chance to die gracefully",
static_cast<int>(get_thread_count()));
mysql_mutex_lock(&LOCK_thread_count);
Thread_iterator it= global_thread_list->begin();
for (; it != global_thread_list->end(); ++it)
{
THD *tmp= *it;
DBUG_PRINT("quit",("Informing thread %ld that it's time to die",
tmp->thread_id));
/* We skip slave threads & scheduler on this first loop through. */
/* 跳过 slave 相关线程，到 end_server() 函数内处理 */
if (tmp->slave_thread)
continue;
if (tmp->get_command() == COM_BINLOG_DUMP ||
tmp->get_command() == COM_BINLOG_DUMP_GTID)
{
++dump_thread_count;
continue;
}
/* 先标记为 KILL 给连接一个自我了断的机会 */
tmp->killed= THD::KILL_CONNECTION;
......
}
mysql_mutex_unlock(&LOCK_thread_count);
Events::deinit();
sql_print_information("Shutting down slave threads");
/* 此处断开 slave 相关线程 */
end_slave();
/* 第二遍遍历线程列表 */
if (dump_thread_count)
{
/*
Replication dump thread should be terminated after the clients are
terminated. Wait for few more seconds for other sessions to end.
*/
while (get_thread_count() > dump_thread_count && dump_thread_kill_retries)
{
sleep(1);
dump_thread_kill_retries--;
}
mysql_mutex_lock(&LOCK_thread_count);
for (it= global_thread_list->begin(); it != global_thread_list->end(); ++it)
{
THD *tmp= *it;
DBUG_PRINT("quit",("Informing dump thread %ld that it's time to die",
tmp->thread_id));
if (tmp->get_command() == COM_BINLOG_DUMP ||
tmp->get_command() == COM_BINLOG_DUMP_GTID)
{
/* 关闭DUMP线程 */
tmp->killed= THD::KILL_CONNECTION;
......
}
}
mysql_mutex_unlock(&LOCK_thread_count);
}
......
/* 第三遍遍历线程列表 */
for (it= global_thread_list->begin(); it != global_thread_list->end(); ++it)
{
THD *tmp= *it;
if (tmp->vio_ok())
{
if (log_warnings)
sql_print_warning(ER_DEFAULT(ER_FORCING_CLOSE),my_progname,
tmp->thread_id,
(tmp->main_security_ctx.user ?
tmp->main_security_ctx.user : ""));
/* 关闭连接，不等待语句结束，但是要回滚未提交线程 */
close_connection(tmp);
}
}
close_connection() 中调用 THD::disconnect() 断开连接
连接断开后开始回滚事务
bool do_command(THD *thd)
{
......
packet_length= my_net_read(net); // thd->disconnect() 后此处直接返回
......
}
void do_handle_one_connection(THD *thd_arg)
{
......
while (thd_is_connection_alive(thd))
{
if (do_command(thd)) //do_command 返回 error，跳出循环
break;
}
end_connection(thd);
end_thread:
close_connection(thd);
/* 此处调用one_thread_per_connection_end() */
if (MYSQL_CALLBACK_ELSE(thd->scheduler, end_thread, (thd, 1), 0))
return; // Probably no-threads
......
}
事务回滚调用链
trans_rollback(THD*) ()
THD::cleanup() ()
THD::release_resources() ()
one_thread_per_connection_end(THD*, bool) ()
do_handle_one_connection(THD*) ()
handle_one_connection ()
unireg_end 调用 clean_up()
void clean_up(bool print_message)
{
/* 这里是一些释放内存和锁的操作 */
......
/*
这里调用 innobase_shutdown_for_mysql
purge all (innodb_fast_shutdown = 0)
merge change buffer (innodb_fast_shutdown = 0）
flush dirty page (innodb_fast_shutdown = 0,1)
flush log buffer
都在这里面做
*/
plugin_shutdown();
/* 这里是一些释放内存和锁的操作 */
......
/*
删除 pid 文件，删除后 mysqld_safe不会重启 mysqld，
不然会认为 mysqld crash，尝试重启
*/
delete_pid_file(MYF(0));
/* 这里是一些释放内存和锁的操作 */
......
innodb shutdown 分析
innodb shutdown 的主要操作在 logs_empty_and_mark_files_at_shutdown() 中
- 等待后台线程结束
- srv_error_monitor_thread
- srv_lock_timeout_thread
- srv_monitor_thread
- buf_dump_thread
- dict_stats_thread
- 等待所有事物结束 trx_sys_any_active_transactions
- 等待后台线程结束
- worker threads: srv_worker_thread
- master thread: srv_master_thread
- purge thread: srv_purge_coordinator_thread
- 等待 buf_flush_lru_manager_thread 结束
- 等待 buf_flush_page_cleaner_thread 结束
- 等待 Pending checkpoint_writes, Pending log flush writes 结束
- 等待 buffer pool pending io 结束
- if (innodb_fast_shutdown == 2)
- flush log buffer 后 return
- log_make_checkpoint_at
- flush buffer pool
- write checkpoint
- 将 lsn 落盘 fil_write_flushed_lsn_to_data_files()
- 关闭所有文件
logs_empty_and_mark_files_at_shutdown() 结束后，innobase_shutdown_for_mysql() 再做一些资源清理工作即结束 shutdown 过程
