因单个程序访问redis流量超出980Mb，单个redis不能满足业务需要，需要做redis主从，让单个程序从redis从只读，主的数据为1.7G，做完从后，发现数据没有同步过来，查看从库日志
18546:S 27 Dec 11:31:01.738 * Connecting to MASTER 192.170.5.88:6379
18546:S 27 Dec 11:31:01.738 * MASTER <-> SLAVE sync started
18546:S 27 Dec 11:31:01.738 * Non blocking connect for SYNC fired the event.
18546:S 27 Dec 11:31:01.740 * Master replied to PING, replication can continue...
18546:S 27 Dec 11:31:01.742 * Partial resynchronization not possible (no cached master)
18546:S 27 Dec 11:31:01.924 * Full resync from master: 8a8b019dfa1192f81f404c68075d4c5dbc0467fd:473627650
18546:S 27 Dec 11:32:34.235 * MASTER <-> SLAVE sync: receiving 1824088898 bytes from master
18546:S 27 Dec 11:32:47.160 # I/O error trying to sync with MASTER: connection lost
18546:S 27 Dec 11:32:48.154 * Connecting to MASTER 192.170.5.88:6379
18546:S 27 Dec 11:32:48.154 * MASTER <-> SLAVE sync started
18546:S 27 Dec 11:32:48.155 * Non blocking connect for SYNC fired the event.
18546:S 27 Dec 11:32:48.155 * Master replied to PING, replication can continue...
18546:S 27 Dec 11:32:48.167 * Partial resynchronization not possible (no cached master)
18546:S 27 Dec 11:32:48.428 * Full resync from master: 8a8b019dfa1192f81f404c68075d4c5dbc0467fd:614945359
18546:S 27 Dec 11:34:21.233 * MASTER <-> SLAVE sync: receiving 1823925331 bytes from master
18546:S 27 Dec 11:34:27.113 # I/O error trying to sync with MASTER: connection lost
##错误I/O error trying to sync with MASTER: connection lost
再来查看主库日志，发现在redis主库在接到从库要求重新同步数据的时候先生成一个rdb文件，再通过psync来做部分同步，可以看到问题就出在部分同步这一块，由于client-output-buffer-limit值设置太小，导致导数发送失败。失败后，从库继续发起数据同步的请求，但是每次都失败，redis主库反复地生成rdb文件，虽然是有fork一个子进程，但是对redis主库的吞吐量是有一定影响的。
解决问题：
在主库操作
127.0.0.1:6379> config get client-output-buffer-limit
1) "client-output-buffer-limit"
2) "normal 0 0 0 slave 268435456 67108864 60 pubsub 33554432 8388608 60"
可以看到，目前的限制是最大256M和60s内不超过64M,从我们上面日志信息可以看到psync的数据明显是大于256M的。我们进行如下设置把很限制调大：
config set client-output-buffer-limit 'slave 1073741824 268435456 60'
调完后再观察，发现从库的的复制状态很快就变成了up。
我们上面的调整是加大复制输出缓冲区，还有一个办法就是关闭复制输出缓冲区的限制：
config set client-output-buffer-limit 'slave 0 0 0'
