前幾天，有位朋友微信聯(lián)系我，告知一個生產(chǎn)數(shù)據(jù)庫，在機(jī)器宕機(jī)恢復(fù)后，實(shí)例啟動失敗，而且該實(shí)例沒有做任何的高可用、容災(zāi)、備份等，對業(yè)務(wù)影響非常大，希望能夠協(xié)助排查一下，我也在第一時間就加入到排查中。

（1）首先查看錯誤日志，報錯很清晰'Could not open log file'，無法打開日志文件

2021-01-06 13:23:51 20464 [ERROR] Failed to open log (file ’something is definitely wrong and this may fail.’, errno 2)2021-01-06 13:23:51 20464 [ERROR] Could not open log file2021-01-06 13:23:51 20464 [ERROR] Can’t init tc log2021-01-06 13:23:51 20464 [ERROR] Aborting

（2）看到上述報錯后，當(dāng)然就應(yīng)該想到，檢查下my.cnf配置是否正確、日志目錄和權(quán)限是否正確，但排查并未發(fā)現(xiàn)問題

# less my.cnfdatadir=/var/lib/mysqllog-bin=mysql-binrelay-log=relay-bin# ls -lrt-rw-rw---- 1 mysql mysql 1073761373 Jan 4 06:18 mysql-bin.007351-rw-rw---- 1 mysql mysql 1073755587 Jan 4 09:26 mysql-bin.007352-rw-rw---- 1 mysql mysql 1073777045 Jan 4 12:07 mysql-bin.007353-rw-rw---- 1 mysql mysql 1073742801 Jan 4 15:12 mysql-bin.007354-rw-rw---- 1 mysql mysql 1074087344 Jan 4 18:13 mysql-bin.007355-rw-rw---- 1 mysql mysql 1073869414 Jan 4 21:32 mysql-bin.007356-rw-rw---- 1 mysql mysql 1073771900 Jan 5 00:16 mysql-bin.007357-rw-rw---- 1 mysql mysql 213063247 Jan 5 01:00 mysql-bin.007358-rw-rw---- 1 mysql mysql 1073753668 Jan 5 02:11 mysql-bin.007359-rw-rw---- 1 mysql mysql 671219722 Jan 5 03:31 mysql-bin.007360-rw-rw---- 1 mysql mysql 1073774928 Jan 5 07:34 mysql-bin.007361-rw-rw---- 1 mysql mysql 1073845285 Jan 5 11:33 mysql-bin.007362-rw-rw---- 1 mysql mysql 1073756444 Jan 5 15:37 mysql-bin.007363-rw-rw---- 1 mysql mysql 1073790555 Jan 5 19:37 mysql-bin.007364-rw-rw---- 1 mysql mysql 1073768027 Jan 5 23:59 mysql-bin.007365-rw-rw---- 1 mysql mysql 311398643 Jan 6 01:00 mysql-bin.007366-rw-rw---- 1 mysql mysql 1071242043 Jan 6 03:31 mysql-bin.007367-rw-rw---- 1 mysql mysql 1010516229 Jan 6 07:27 mysql-bin.007368-rw-rw---- 1 mysql mysql 1651 Jan 6 07:27 mysql-bin.index-rw-rw---- 1 mysql mysql 1073741824 Jan 6 12:08 ib_logfile1-rw-r--r-- 1 mysql mysql 183 Jan 6 13:23 VM_58_10_centos-slow.log-rw-rw---- 1 mysql mysql 1073741824 Jan 6 13:23 ib_logfile0-rw-rw---- 1 mysql mysql 7492941 Jan 6 13:23 VM_58_10_centos.err

（3）報錯有一個非常奇怪的點(diǎn)，file ’something is definitely wrong and this may fail.’ ，為什么日志文件名會那么奇怪呢？這里需要知道的是，mysql-bin.index記錄了binlog相關(guān)信息，MySQL實(shí)例啟動時需要讀取該文件獲取信息；那接下來就檢查一下該文件，發(fā)現(xiàn)果然有問題，mysql-bin.index后半部分錯誤寫入了錯誤日志的內(nèi)容，從而導(dǎo)致實(shí)例啟動時讀取到錯誤內(nèi)容(當(dāng)作binlog日志文件進(jìn)行處理)報錯失敗

# cat mysql-bin.index ./mysql-bin.007351./mysql-bin.007352./mysql-bin.007353./mysql-bin.007354./mysql-bin.007355./mysql-bin.007356./mysql-bin.007357./mysql-bin.007358./mysql-bin.007359./mysql-bin.007360./mysql-bin.007361./mysql-bin.007362./mysql-bin.007363./mysql-bin.007364./mysql-bin.007365./mysql-bin.007366./mysql-bin.007367./mysql-bin.00736823:27:31 UTC - mysqld got signal 6 ;This could be because you hit a bug. It is also possible that this binaryor one of the libraries it was linked against is corrupt, improperly built,or misconfigured. This error can also be caused by malfunctioning hardware.We will try our best to scrape up some info that will hopefully helpdiagnose the problem, but since we have already crashed, something is definitely wrong and this may fail.key_buffer_size=16777216read_buffer_size=3145728max_used_connections=523max_threads=800thread_count=522connection_count=522It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 9037821 K bytes of memoryHope that’s ok; if not, decrease some variables in the equation.Thread pointer: 0x0Attempting backtrace. You can use the following information to find outwhere mysqld died. If you see no messages after this, something wentterribly wrong...stack_bottom = 0 thread_stack 0x40000The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html containsinformation that should help you find out what is causing the crash.

（4）原因定位后，解決辦法就是將mysql-bin.index文件備份后，手動進(jìn)行修復(fù)，隨后啟動實(shí)例成功

# ./mysql startStarting MySQL.... SUCCESS! Checking mysql connection: connection ok!# ps -ef | grep mysqldroot 22955 1 0 13:30 pts/5 00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --pid-file=/var/lib/mysql/VM_58_10_centos.pidmysql 23733 22955 24 13:30 pts/5 00:00:05 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/VM_58_10_centos.err --open-files-limit=20000 --pid-file=/var/lib/mysql/VM_58_10_centos.pid --socket=/var/lib/mysql/mysql.sock --port=3306root 32075 14929 0 13:30 pts/5 00:00:00 grep mysqld總結(jié)

至此，問題得到解決，至于為什么錯誤日志內(nèi)容會寫入到mysql-bin.index，個人懷疑是宕機(jī)導(dǎo)致文件錯亂(該宿主機(jī)上的其他虛擬機(jī)有出現(xiàn)文件系統(tǒng)損壞的情況)；最后，還是得強(qiáng)調(diào)一下，生產(chǎn)系統(tǒng)還是得重視起來，備份、高可用、容災(zāi)都是不可或缺的。

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