Innodb monitor介绍

学习oracle的时候，如果想了解一些内部原理和机制，可以使用一些event来生成trace文件，通过分析这些trace文件可以获得很多的信息。而MySQL在这方面比较弱，当然，另一方面来说，MySQL是开源的，可以去直接研究源代码的实现。不过源代码架构庞大，不是每个人都有足够的精力和毅力去解读。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 308229Mutex spin waits 0, rounds 18209349, OS waits 111906RW-shared spins 287775, OS waits 142204; RW-excl spins 175036, OS waits 19318------------TRANSACTIONS------------Trx id counter 0 121675664Purge done for trx's n:o < 0 121675662 undo n:o < 0 0History list length 10LIST OF TRANSACTIONS FOR EACH SESSION:---TRANSACTION 0 121462143, not started, process no 8452, OS thread id 1160767840mysql tables in use 1, locked 1MySQL thread id 8056144, query id 78206864 localhost root---TRANSACTION 0 137229, not started, process no 8452, OS thread id 1158199648MySQL 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: 0Pending flushes (fsync) log: 0; buffer pool: 034 OS file reads, 80820900 OS file writes, 1263117 OS fsyncs0.00 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 mergesHash 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 3697502095Log flushed up to   4 3697502095Last checkpoint at  4 36975020950 pending log writes, 0 pending chkp writes79595438 log i/o's done, 0.47 log i/o's/second----------------------BUFFER POOL AND MEMORY----------------------Total memory allocated 4851752298; in additional pool allocated 13195520Dictionary memory allocated 145784Buffer pool size   262144Free buffers       193334Database pages     68577Modified db pages  0Pending reads 0Pending writes: LRU 0, flush list 0, single page 0Pages read 70, created 120513, written 28299670.00 reads/s, 0.21 creates/s, 0.84 writes/sBuffer pool hit rate 1000 / 1000--------------ROW OPERATIONS--------------0 queries inside InnoDB, 0 queries in queue1 read views open inside InnoDBMain thread process no. 8452, id 1157658976, state: waiting for server activityNumber of rows inserted 12233742, updated 57497659, deleted 1, read 697200500.05 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 0size 65536, free limit 6208, free extents 89not full frag extents 6: used pages 69, full frag extents 0first seg id not used 0 1067667SEGMENT id 0 1067666 space 0; page 903; res 1 used 1; full ext 0fragm 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 0fragm pages 1; free extents 0; not full extents 0: pages 0NUMBER of file segments: 37Validating tablespaceValidation ok---------------------------------------END OF INNODB TABLESPACE MONITOR OUTPUT=======================================

from：http://www.ningoo.net/html/2009/an_introduce_of_innodb_monitor.html