redis 4 增量同步的日志详解


1、1主 2从 环境下，关闭原先的master节点


2、在新的master上执行 slaveof no one

看到的日志:

6855:M 02 Sep 15:43:16.871 # Setting secondary replication ID to 2ba403b0a69dcacbfe92650ac8758ae236693d5c, valid up to offset: 4802. New replication ID is 5f01e7a777abda968d9765145d5bc09146226615

6855:M 02 Sep 15:43:16.871 * Discarding previously cached master state.

6855:M 02 Sep 15:43:16.871 * MASTER MODE enabled (user request from 'id=3 addr=127.0.0.1:59204 fd=8 name= age=3041 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=slaveof')

6855:M 02 Sep 15:43:33.820 * 1 changes in 900 seconds. Saving...

6855:M 02 Sep 15:43:33.840 * Background saving started by pid 6929

6929:C 02 Sep 15:43:33.854 * DB saved on disk

6929:C 02 Sep 15:43:33.855 * RDB: 0 MB of memory used by copy-on-write

6855:M 02 Sep 15:43:33.941 * Background saving terminated with success

###日志解说：

2ba403b0a69dcacbfe92650ac8758ae236693d5c 这个是 宕机的原先master的runid

5f01e7a777abda968d9765145d5bc09146226615 这个是 新的master的runid

可以看到，新的master 在提升为主的时候，还记录了之前复制到的pos和之前主库的runid


3、然后，新的slave上执行 slaveof 127.0.0.1 6379

看到的日志：

6923:S 02 Sep 15:43:59.751 * SLAVE OF 127.0.0.1:6379 enabled (user request from 'id=3 addr=127.0.0.1:42122 fd=8 name= age=115 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=slaveof')

6923:S 02 Sep 15:44:00.427 * Connecting to MASTER 127.0.0.1:6379

6923:S 02 Sep 15:44:00.427 * MASTER <-> SLAVE sync started

6923:S 02 Sep 15:44:00.427 * Non blocking connect for SYNC fired the event.

6923:S 02 Sep 15:44:00.427 * Master replied to PING, replication can continue...

6923:S 02 Sep 15:44:00.428 * Trying a partial resynchronization (request 2ba403b0a69dcacbfe92650ac8758ae236693d5c:4802). # 可以看到，从库在连接到新的主库时候，会把之前的主库复制的runid和pos发送给新master，尝试增量同步数据

6923:S 02 Sep 15:44:00.429 * Successful partial resynchronization with master.

6923:S 02 Sep 15:44:00.429 # Master replication ID changed to 5f01e7a777abda968d9765145d5bc09146226615

6923:S 02 Sep 15:44:00.429 * MASTER <-> SLAVE sync: Master accepted a Partial Resynchronization.


4、然后，再看下新的master的日志：

6855:M 02 Sep 15:44:00.428 * Slave 127.0.0.1:6381 asks for synchronization

6855:M 02 Sep 15:44:00.428 * Partial resynchronization request from 127.0.0.1:6381 accepted. Sending 128 bytes of backlog starting from offset 4802.

可看到，新master也同意了slave的增量复制的请求。