InnoDB Monitor。用InnoDB monitor 可以监控死锁的情况等。

InnoDB引擎提供了一个monitor，可以通过monitor一窥其内部的一些统计信息，也可以说是了解InnoDB引擎的一个很好的窗口。

我们最熟悉的，应当就是show innodb status命令，可以直接在客户端输出很多的信息。其实InnoDB monitor一共有四种模式，show innodb status只是其一种模式的直接展现，并且只能交互式开启，无法自动循环捕获信息。另外还有一种适合四种模式的开启方式，则是通过创建一张特殊的innodb表来开启，开启后会按照固定的时间间隔循环，输出信息到log-error参数指定的错误日志文件中，通过drop对应的表，可以停止monitor。

四种monitor分别是:

innodb_monitor：create table innodb_monitor(x int) engine=innodb;
innodb_lock_monitor：create table innodb_lock_monitor(x int) engine=innodb;
innodb_table_monitor：create table innodb_table_monitor(x int) engine=innodb;
innodb_tablespace_monitor：create table innodb_tablespace_monitor(x int) engine=innodb;
根据我在5.1.36版本中实际观察到的结果，innodb_monitor/innodb_lock_monitor开启后的执行周期是16s（参考手册上说是15s），而innodb_table_monitor/innodb_tablespace_monitor的执行周期是64s。开启monitor后因为是持续周期性的运行的，在不需要的时候一定要记得drop相关表来停止monitor。如果在开启monitor的中间服务器有重启，monitor不会自动重启，并且在下次启动monitor之前，必须先执行停止操作。

其中innodb_monitor/innodb_lock_monitor两种监视器的输出结果基本类似，后者会有更多关于锁的信息，而前一个实际上就是show innodb status。innodb_table_monitor则会将系统中所有innodb的表的一些结构和内部信息输出，而innodb_tablespace_monitor则输出的是tablespace的信息，注意该monitor输出的只是共享表空间的信息，如果使用innodb_file_per_table为每个表使用独立的表空间，则这些表空间的信息是不会包含在输出中的。

以下是一些简单的示例：
innodb_monitor/innodb_lock_monitor：

===================================== 090805 22:24:48 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 19 seconds ———- SEMAPHORES ———- OS WAIT ARRAY INFO: reservation count 312921, signal count 308229 Mutex spin waits 0, rounds 18209349, OS waits 111906 RW-shared spins 287775, OS waits 142204; RW-excl spins 175036, OS waits 19318 ———— TRANSACTIONS ———— Trx id counter 0 121675664 Purge done for trx’s n:o < 0 121675662 undo n:o < 0 0 History list length 10 LIST OF TRANSACTIONS FOR EACH SESSION: —TRANSACTION 0 121462143, not started, process no 8452, OS thread id 1160767840 mysql tables in use 1, locked 1 MySQL thread id 8056144, query id 78206864 localhost root —TRANSACTION 0 137229, not started, process no 8452, OS thread id 1158199648 MySQL thread id 50, query id 377 Has read all relay log; waiting for the slave I/O thread to update it ——– FILE I/O ——– I/O thread 0 state: waiting for i/o request (insert buffer thread) I/O thread 1 state: waiting for i/o request (log thread) I/O thread 2 state: waiting for i/o request (read thread) I/O thread 3 state: waiting for i/o request (write thread) Pending normal aio reads: 0, aio writes: 0, ibuf aio reads: 0, log i/o’s: 0, sync i/o’s: 0 Pending flushes (fsync) log: 0; buffer pool: 0 34 OS file reads, 80820900 OS file writes, 1263117 OS fsyncs 0.00 reads/s, 0 avg bytes/read, 1.16 writes/s, 0.63 fsyncs/s ————————————- INSERT BUFFER AND ADAPTIVE HASH INDEX ————————————- Ibuf: size 1, free list len 0, seg size 2, 0 inserts, 0 merged recs, 0 merges Hash table size 8850487, node heap has 233 buffer(s) 0.11 hash searches/s, 0.42 non-hash searches/s — LOG — Log sequence number 4 3697502095 Log flushed up to 4 3697502095 Last checkpoint at 4 3697502095 0 pending log writes, 0 pending chkp writes 79595438 log i/o’s done, 0.47 log i/o’s/second ———————- BUFFER POOL AND MEMORY ———————- Total memory allocated 4851752298; in additional pool allocated 13195520 Dictionary memory allocated 145784 Buffer pool size 262144 Free buffers 193334 Database pages 68577 Modified db pages 0 Pending reads 0 Pending writes: LRU 0, flush list 0, single page 0 Pages read 70, created 120513, written 2829967 0.00 reads/s, 0.21 creates/s, 0.84 writes/s Buffer pool hit rate 1000 / 1000 ————– ROW OPERATIONS ————– 0 queries inside InnoDB, 0 queries in queue 1 read views open inside InnoDB Main thread process no. 8452, id 1157658976, state: waiting for server activity Number of rows inserted 12233742, updated 57497659, deleted 1, read 69720050 0.05 inserts/s, 0.05 updates/s, 0.00 deletes/s, 0.05 reads/s —————————- END OF INNODB MONITOR OUTPUT ============================
innodb_table_monitor：

=========================================== 090805 22:26:56 INNODB TABLE MONITOR OUTPUT =========================================== ————————————– TABLE: name SYS_FOREIGN, id 0 11, columns 7, indexes 3, appr.rows 0 COLUMNS: ID: DATA_VARCHAR prtype 1835012 len 0; FOR_NAME: DATA_VARCHAR prtype 1835012 len 0; REF_NAME: DATA_VARCHAR prtype 1835012 len 0; N_COLS: DATA_INT len 4; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name ID_IND, id 0 11, fields 1/6, uniq 1, type 3 root page 46, appr.key vals 0, leaf pages 1, size pages 1 FIELDS: ID DB_TRX_ID DB_ROLL_PTR FOR_NAME REF_NAME N_COLS INDEX: name FOR_IND, id 0 12, fields 1/2, uniq 2, type 0 root page 47, appr.key vals 0, leaf pages 1, size pages 1 FIELDS: FOR_NAME ID INDEX: name REF_IND, id 0 13, fields 1/2, uniq 2, type 0 root page 48, appr.key vals 0, leaf pages 1, size pages 1 FIELDS: REF_NAME ID …省略若干输出 ————————————– TABLE: name test/test, id 0 81, columns 4, indexes 1, appr.rows 3 COLUMNS: i: DATA_INT DATA_BINARY_TYPE len 4; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name GEN_CLUST_INDEX, id 0 23, fields 0/4, uniq 1, type 1 root page 3, appr.key vals 3, leaf pages 1, size pages 1 FIELDS: DB_ROW_ID DB_TRX_ID DB_ROLL_PTR i ———————————– END OF INNODB TABLE MONITOR OUTPUT ==================================
innodb_tablespace_monitor：

================================================ 090805 22:28:16 INNODB TABLESPACE MONITOR OUTPUT ================================================ FILE SPACE INFO: id 0 size 65536, free limit 6208, free extents 89 not full frag extents 6: used pages 69, full frag extents 0 first seg id not used 0 1067667 SEGMENT id 0 1067666 space 0; page 903; res 1 used 1; full ext 0 fragm pages 1; free extents 0; not full extents 0: pages 0 …省略若干输出 SEGMENT id 0 144216 space 0; page 1307; res 1 used 1; full ext 0 fragm pages 1; free extents 0; not full extents 0: pages 0 NUMBER of file segments: 37 Validating tablespace Validation ok ————————————— END OF INNODB TABLESPACE MONITOR OUTPUT =======================================