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這個月初，通過zabbix監控發現有1臺mysql數據庫的從庫內存剩余空間不斷降低。檢查以往的監控歷史圖表，發現由于內存占用不斷增大，每隔一個多月，就會因為內存嚴重不足，導致這臺服務器的1個mysql實例（端口：3316）重啟。數據庫實例重啟之后，內存被大量釋放，但經過一個多月，又會因為不斷占用的內存再次重啟mysql實例。
上圖是這臺服務器的zabbix監控圖形，近半年來3次內存枯竭的時間分別是去年10月27日、12月25日、今年2月8日。
執行“top”命令，可以快速找到是那個mysql實例的進程PID：
[root@DB3 data1]# top top - 14:06:03 up 829 days, 5 min, 1 user, load average: 0.00, 0.02, 0.05 Tasks: 167 total, 1 running, 166 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.2 us, 0.1 sy, 0.0 ni, 99.5 id, 0.2 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 32520424 total, 14101408 used, 18419016 free, 144168 buffers KiB Swap: 0 total, 0 used, 0 free. 1240256 cached Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3348 mysql 20 0 6048008 4.340g 7436 S 1.0 14.0 48:20.58 mysqld 1039 mysql 20 0 32.919g 5.942g 0 S 0.3 19.2 923:58.09 mysqld 18301 root 20 0 123692 1672 1176 R 0.3 0.0 0:00.02 top 1 root 20 0 41108 2384 1232 S 0.0 0.0 8:53.72 systemd 2 root 20 0 0 0 0 S 0.0 0.0 0:05.82 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 1:30.15 ksoftirqd/0 5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H 7 root rt 0 0 0 0 S 0.0 0.0 0:21.02 migration/0 8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh 9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/0 10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/1 11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/2 12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/3 13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/4 14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/5 15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/6 16 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/7 17 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/8 18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/9 19 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/10 20 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/11 21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/12 22 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/13 23 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/14 24 root 20 0 0 0 0 S 0.0 0.0 373:05.02 rcu_sched
執行“ps -ef|grep mysql”命令，就可以根據上面的PID，找到是3316端口的mysql實例：
[root@DB3 data1]# ps -ef|grep mysql mysql 1039 26090 0 2017 ? 15:23:58 /usr/local/mysql/bin/mysqld --basedir=/usr/local/mysql --datadir=/mysql/data/ --plugin-dir=/usr/local/mysql/lib/mysql/plugin --user=mysql --log-error=/mysql/data/mysql-error.log --open-files-limit=65535 --pid-file=/mysql/data/mysql.pid --socket=/mysql/data/mysql.sock mysql 3348 5231 0 Mar15 ? 00:48:20 /usr/local/mysql/bin/mysqld --defaults-extra-file=/mysql/data1/my.cnf --basedir=/usr/local/mysql --datadir=/mysql/data1/ --plugin-dir=/usr/local/mysql/lib/mysql/plugin --user=mysql --log-error=/mysql/data1/mysql-error.log --open-files-limit=65535 --pid-file=/mysql/data1/mysql.pid --socket=/mysql/data1/mysql.sock --port=3316 root 5231 1 0 2016 ? 00:00:00 /bin/sh /usr/local/mysql/bin/mysqld_safe --defaults-extra-file=/mysql/data1/my.cnf --datadir=/mysql/data1/ --user=mysql root 18327 17987 0 14:06 pts/2 00:00:00 grep --color=auto mysql root 26090 1 0 2016 ? 00:00:00 /bin/sh /usr/local/mysql/bin/mysqld_safe --datadir=/mysql/data/ --pid-file=/mysql/data/mysql.pid
3316這個實例是rabbitMQ持久化存儲數據用的，最初我懷疑可能與持久化出問題有關。
但是，運維同事根據數據庫的錯誤日志，認為是mysql的配置參數設置不當有關。
[root@DB3 ~]# cd /mysql/data1/ [root@DB3 data1]# ll -tr total 1607352 drwx------ 2 mysql mysql 6 Nov 28 2016 test drwx------ 2 mysql mysql 4096 Nov 28 2016 performance_schema drwx------ 2 mysql mysql 4096 Nov 28 2016 mysql -rwxr-xr-x 1 root root 127 Nov 28 2016 start_mysql_3316.sh -rw-rw---- 1 mysql mysql 56 Nov 28 2016 auto.cnf drwx------ 2 mysql mysql 4096 Nov 28 2016 activemq -rw-rw---- 1 mysql mysql 536870912 Mar 7 13:09 ib_logfile1 -rw-r--r-- 1 root root 2455 Mar 15 09:57 my.cnf -rw-rw---- 1 mysql mysql 266186542 Mar 15 18:05 mysql-bin.000012 -rw-rw---- 1 mysql mysql 60 Mar 15 18:05 mysql-bin.index srwxrwxrwx 1 mysql mysql 0 Mar 15 18:05 mysql.sock -rw-rw---- 1 mysql mysql 5 Mar 15 18:05 mysql.pid -rw-r----- 1 mysql root 24166 Mar 15 18:05 mysql-error.log -rw-rw---- 1 mysql mysql 17395510 Mar 19 13:49 mysql-bin.000013 -rw-rw---- 1 mysql mysql 79691776 Mar 19 13:49 ibdata1 -rw-rw---- 1 mysql mysql 536870912 Mar 19 13:49 ib_logfile0 -rw-rw---- 1 mysql mysql 204840084 Mar 19 13:49 mysql-slow.log [root@DB3 data1]# tail -90 mysql-error.log 2018-02-07 19:59:28 12413 [Note] InnoDB: Compressed tables use zlib 1.2.3 2018-02-07 19:59:28 12413 [Note] InnoDB: Using Linux native AIO 2018-02-07 19:59:28 12413 [Note] InnoDB: Using CPU crc32 instructions 2018-02-07 19:59:28 12413 [Note] InnoDB: Initializing buffer pool, size = 26.0G 2018-02-07 19:59:30 12413 [Note] InnoDB: Completed initialization of buffer pool 2018-02-07 19:59:30 12413 [Note] InnoDB: Highest supported file format is Barracuda. 2018-02-07 19:59:30 12413 [Note] InnoDB: The log sequence numbers 1625987 and 1625987 in ibdata files do not match the log sequence number 12657781043 in the ib_logfiles! 2018-02-07 19:59:30 12413 [Note] InnoDB: Database was not shutdown normally! 2018-02-07 19:59:30 12413 [Note] InnoDB: Starting crash recovery. 2018-02-07 19:59:30 12413 [Note] InnoDB: Reading tablespace information from the .ibd files... 2018-02-07 19:59:30 12413 [Note] InnoDB: Restoring possible half-written data pages 2018-02-07 19:59:30 12413 [Note] InnoDB: from the doublewrite buffer... InnoDB: 1 transaction(s) which must be rolled back or cleaned up InnoDB: in total 127441 row operations to undo InnoDB: Trx id counter is 10797056 InnoDB: Last MySQL binlog file position 0 793055160, file name mysql-bin.000011 2018-02-07 19:59:32 12413 [Note] InnoDB: 128 rollback segment(s) are active. InnoDB: Starting in background the rollback of uncommitted transactions 2018-02-07 19:59:32 7fd34afa8700 InnoDB: Rolling back trx with id 10003975, 127441 rows to undo InnoDB: Progress in percents: 12018-02-07 19:59:32 12413 [Note] InnoDB: Waiting for purge to start 2018-02-07 19:59:32 12413 [Note] InnoDB: Percona XtraDB (http://www.percona.com) 5.6.27-76.0 started; log sequence number 12657781043 22018-02-07 19:59:33 12413 [Note] Recovering after a crash using /mysql/data1/mysql-bin 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 1002018-02-07 19:59:33 12413 [Note] InnoDB: Rollback of trx with id 10003975 completed 2018-02-07 19:59:33 7fd34afa8700 InnoDB: Rollback of non-prepared transactions completed 2018-02-07 19:59:51 12413 [Note] Starting crash recovery... 2018-02-07 19:59:51 12413 [Note] Crash recovery finished. 2018-02-07 19:59:51 12413 [Note] Server hostname (bind-address): '*'; port: 3316 2018-02-07 19:59:51 12413 [Note] IPv6 is available. 2018-02-07 19:59:51 12413 [Note] - '::' resolves to '::'; 2018-02-07 19:59:51 12413 [Note] Server socket created on IP: '::'. 2018-02-07 19:59:51 12413 [Warning] 'user' entry 'root@db3' ignored in --skip-name-resolve mode. 2018-02-07 19:59:51 12413 [Warning] 'user' entry '@db3' ignored in --skip-name-resolve mode. 2018-02-07 19:59:51 12413 [Warning] 'proxies_priv' entry '@ root@db3' ignored in --skip-name-resolve mode. 2018-02-07 19:59:51 12413 [Note] Event Scheduler: Loaded 0 events 2018-02-07 19:59:51 12413 [Note] /usr/local/mysql/bin/mysqld: ready for connections. Version: '5.6.27-76.0-log' socket: '/mysql/data1/mysql.sock' port: 3316 Source distribution 180315 18:04:56 mysqld_safe Number of processes running now: 0 180315 18:04:56 mysqld_safe mysqld restarted 2018-03-15 18:04:57 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details). 2018-03-15 18:04:57 0 [Warning] 'ERROR_FOR_DIVISION_BY_ZERO' is deprecated and will be removed in a future release. 2018-03-15 18:04:57 0 [Warning] 'NO_ZERO_DATE' is deprecated and will be removed in a future release. 2018-03-15 18:04:57 0 [Warning] 'NO_ZERO_IN_DATE' is deprecated and will be removed in a future release. 2018-03-15 18:04:57 0 [Note] /usr/local/mysql/bin/mysqld (mysqld 5.6.27-76.0-log) starting as process 3348 ... 2018-03-15 18:04:57 3348 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead. 2018-03-15 18:04:57 3348 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead. 2018-03-15 18:04:57 3348 [Note] Plugin 'FEDERATED' is disabled. 2018-03-15 18:04:57 3348 [Warning] The option innodb (skip-innodb) is deprecated and will be removed in a future release 2018-03-15 18:04:57 3348 [Warning] The option innodb (skip-innodb) is deprecated and will be removed in a future release 2018-03-15 18:04:57 3348 [Note] InnoDB: Using atomics to ref count buffer pool pages 2018-03-15 18:04:57 3348 [Note] InnoDB: The InnoDB memory heap is disabled 2018-03-15 18:04:57 3348 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins 2018-03-15 18:04:57 3348 [Note] InnoDB: Memory barrier is not used 2018-03-15 18:04:57 3348 [Note] InnoDB: Compressed tables use zlib 1.2.3 2018-03-15 18:04:57 3348 [Note] InnoDB: Using Linux native AIO 2018-03-15 18:04:57 3348 [Note] InnoDB: Using CPU crc32 instructions 2018-03-15 18:04:57 3348 [Note] InnoDB: Initializing buffer pool, size = 2.0G 2018-03-15 18:04:57 3348 [Note] InnoDB: Completed initialization of buffer pool 2018-03-15 18:04:57 3348 [Note] InnoDB: Highest supported file format is Barracuda. 2018-03-15 18:04:57 3348 [Note] InnoDB: The log sequence numbers 1625987 and 1625987 in ibdata files do not match the log sequence number 12972128167 in the ib_logfiles! 2018-03-15 18:04:57 3348 [Note] InnoDB: Database was not shutdown normally! 2018-03-15 18:04:57 3348 [Note] InnoDB: Starting crash recovery. 2018-03-15 18:04:57 3348 [Note] InnoDB: Reading tablespace information from the .ibd files... 2018-03-15 18:04:58 3348 [Note] InnoDB: Restoring possible half-written data pages 2018-03-15 18:04:58 3348 [Note] InnoDB: from the doublewrite buffer... InnoDB: 1 transaction(s) which must be rolled back or cleaned up InnoDB: in total 103450 row operations to undo InnoDB: Trx id counter is 11109120 InnoDB: Last MySQL binlog file position 0 266186542, file name mysql-bin.000012 2018-03-15 18:04:59 3348 [Note] InnoDB: 128 rollback segment(s) are active. InnoDB: Starting in background the rollback of uncommitted transactions 2018-03-15 18:04:59 7eff9bd1d700 InnoDB: Rolling back trx with id 10797063, 103450 rows to undo InnoDB: Progress in percents: 12018-03-15 18:04:59 3348 [Note] InnoDB: Waiting for purge to start 2 3 42018-03-15 18:04:59 3348 [Note] InnoDB: Percona XtraDB (http://www.percona.com) 5.6.27-76.0 started; log sequence number 12972128167 5 6 7 8 9 10 11 12 13 14 15 16 172018-03-15 18:04:59 3348 [Note] Recovering after a crash using /mysql/data1/mysql-bin 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 1002018-03-15 18:05:00 3348 [Note] InnoDB: Rollback of trx with id 10797063 completed 2018-03-15 18:05:00 7eff9bd1d700 InnoDB: Rollback of non-prepared transactions completed 2018-03-15 18:05:03 3348 [Note] Starting crash recovery... 2018-03-15 18:05:03 3348 [Note] Crash recovery finished. 2018-03-15 18:05:03 3348 [Note] Server hostname (bind-address): '*'; port: 3316 2018-03-15 18:05:03 3348 [Note] IPv6 is available. 2018-03-15 18:05:03 3348 [Note] - '::' resolves to '::'; 2018-03-15 18:05:03 3348 [Note] Server socket created on IP: '::'. 2018-03-15 18:05:03 3348 [Warning] 'user' entry 'root@db3' ignored in --skip-name-resolve mode. 2018-03-15 18:05:03 3348 [Warning] 'user' entry '@db3' ignored in --skip-name-resolve mode. 2018-03-15 18:05:03 3348 [Warning] 'proxies_priv' entry '@ root@db3' ignored in --skip-name-resolve mode. 2018-03-15 18:05:04 3348 [Note] Event Scheduler: Loaded 0 events 2018-03-15 18:05:04 3348 [Note] /usr/local/mysql/bin/mysqld: ready for connections. Version: '5.6.27-76.0-log' socket: '/mysql/data1/mysql.sock' port: 3316 Source distribution
在上面mysql錯誤日志里，第4行“Initializing buffer pool, size = 26.0G”引起了他的注意，并據此對mysql配置文件做了修改。
[root@DB3 data1]# tail -16 my.cnf # INNODB # innodb-flush-method = O_DIRECT innodb-log-files-in-group = 2 innodb-log-file-size = 512M innodb-flush-log-at-trx-commit = 1 innodb-file-per-table = 1 innodb-buffer-pool-size = 2G # LOGGING # log-error = /mysql/data1/mysql-error.log log-queries-not-using-indexes = 1 slow-query-log = 1 slow-query-log-file = /mysql/data1/mysql-slow.log #slave slave_skip_errors=1062
第7行的參數“innodb-buffer-pool-size”當時配置的有幾十G，他把這個參數修改為“2G”。
這個數據庫實例用于rabbitMQ持久化，而rabbitMQ是提供給電銷使用的。
在電銷部門下午6點下班之后，他通過“ps -ef|grep mysql”找到這個實例，再“kill -9”殺掉這個實例，沒想到，這個實例就立即自己啟動了。
電銷相關的開發同事檢查電銷業務沒有問題后，我們就下班了。
第二天檢查zabbix監控，不僅內存被大量釋放，而且，也沒有再不斷被占用。
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