mysql主要后台线程介绍说明

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本文详细介绍了InnoDB存储引擎中的各类线程，包括masterthread、insertbufferthread、readthread、writethread、logthread、purgethread、lockthread及错误监控线程的功能与职责。同时，展示了如何通过showengineinnodbstatus命令查看这些线程的实时状态。

线程名称	说明
master thread	主要负责将合并也脏缓存页刷到数据文件，执行purge操作，触发检查点，合并插入缓冲区等；
insert buffer thread	主要负责插入缓冲区的合并操作；
read thread	负责数据库读取操作，可以配置多个读线程；
write thread	负责数据库的写操作，可以配置多个写线程；
log thread	用于将重做日志文件刷新到logfile中；
purge thread	mysql5.5之后用单独的purge thread 执行purge操作；
lock thread	负责锁控制和死锁检测等；
错误监控线程	主要负责错误监控和错误处理；

通过show engine innodb status 命令查看线程的状态；


=====================================
2019-09-06 10:37:06 0x7f18c3fbe700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 12 seconds
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
 ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 0; buffer pool: 0
7220497 OS file reads, 1072100 OS file writes, 191589 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s

----------------------------
END OF INNODB MONITOR OUTPUT
============================
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