今天幾臺MySQL服務器突然停電，重啓後複製無法啓動，總是報如下錯誤：
080922 10:29:01 [Note] Slave SQL thread initialized, starting replication in log 'mysql-bin.000778' at position 2874108, relay log '
./relay-bin.003287' position: 2874245
080922 10:29:01 [Note] Slave I/O thread: connected to master '[email protected]:3306', replication started in log 'mysql-b
in.000778' at position 2874108
080922 10:29:01 [ERROR] Error reading packet from server: Client requested master to start replication from impossible position ( se
rver_errno=1236)
080922 10:29:01 [ERROR] Got fatal error 1236: 'Client requested master to start replication from impossible position' from master wh
en reading data from binary log
爲什麼會報impossible position呢？打開mysql-bin.000778看看。
mysqlbinlog mysql-bin.000778 > log.sql
tail -f log.sql
# at 2871574
#080922 10:20:27 server id 2 end_log_pos 2871601 Xid = 2516638
COMMIT/*!*/;
DELIMITER ;
# End of log file
ROLLBACK /* added by mysqlbinlog */;
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/
最後一個position是2871574，而從庫要從2874108開始，難怪報impossible position，難道是斷電時有部分log在緩存中還沒來得及寫入binglog？無論如何先恢復再說吧
stop slave;
CHANGE MASTER TO
MASTER_LOG_FILE='mysql-bin.000778',
MASTER_LOG_POS=2871574;
start slave;
show slave statusG
同步正常。。
後來查看主庫的啓動日誌中這樣一段
InnoDB: Last MySQL binlog file position 0 2874108, file name ./mysql-bin.000778
080922 10:22:09 InnoDB: Started; log sequence number 6 2534366248
080922 10:22:09 [Note] Recovering after a crash using mysql-bin
080922 10:22:09 [Note] Starting crash recovery...
080922 10:22:09 [Note] Crash recovery finished.
080922 10:22:09 [Note] /usr/sbin/mysqld: ready for connections.
這裏Last MySQL binlog file position 0 2874108也是錯誤的，這個信息到底是哪裏來的呢？爲什麼會這樣呢？不明白。
爲了保證以後binglog及時寫入，將主庫sync_binlog變量設置1。
