redis主從複製

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Redis 是一個高效能的key-value資料庫。 redis的出現，很大程度補償了memcached這類keyvalue儲存的不足，在部分場合可以對關聯式資料庫起到很好的補充作用。它提供了Python，Ruby，Erlang，PHP用戶端，使用很方便。

效能測試結果：

SET操作每秒鐘 110000 次，GET操作每秒鐘 81000 次，伺服器配置如下：

Linux 2.6, Xeon X3320 2.5Ghz.

stackoverflow 網站使用 Redis 做為快取服務器。

redis可以做一個主從複製的設定，見redis.conf

################################# REPLICATION ################################## Master-Slave replication. Use slaveof to make a Redis instance a copy of# another Redis server. Note that the configuration is local to the slave# so for example it is possible to configure the slave to save the DB with a# different interval, or to listen to another port, and so on.## slaveof <masterip> <masterport> #主服務ip和連接埠# If the master is password protected (using the "requirepass" configuration# directive below) it is possible to tell the slave to authenticate before# starting the replication synchronization process, otherwise the master will# refuse the slave request.## masterauth <master-password> #如果master設定了密碼，slave需要進行認證# When a slave loses its connection with the master, or when the replication# is still in progress, the slave can act in two different ways:## 1) if slave-serve-stale-data is set to ‘yes‘ (the default) the slave will#    still reply to client requests, possibly with out of date data, or the#    data set may just be empty if this is the first synchronization.## 2) if slave-serve-stale-data is set to ‘no‘ the slave will reply with#    an error "SYNC with master in progress" to all the kind of commands#    but to INFO and SLAVEOF.#

#當slave失去與master的串連，或正在拷貝中，如果為yes，slave會響應用戶端請求，資料可能不同步甚至沒有資料，如果為no，slave會返回錯誤"SYNC with master in progress"

slave-serve-stale-data yes 

# You can configure a slave instance to accept writes or not. Writing against# a slave instance may be useful to store some ephemeral data (because data# written on a slave will be easily deleted after resync with the master) but# may also cause problems if clients are writing to it because of a# misconfiguration.## Since Redis 2.6 by default slaves are read-only.## Note: read only slaves are not designed to be exposed to untrusted clients# on the internet. It‘s just a protection layer against misuse of the instance.# Still a read only slave exports by default all the administrative commands# such as CONFIG, DEBUG, and so forth. To a limited extend you can improve# security of read only slaves using ‘rename-command‘ to shadow all the# administrative / dangerous commands.
slave-read-only yes #從伺服器唯讀，不可寫# Slaves send PINGs to server in a predefined interval. It‘s possible to change# this interval with the repl_ping_slave_period option. The default value is 10# seconds.## repl-ping-slave-period 10# The following option sets a timeout for both Bulk transfer I/O timeout and# master data or ping response timeout. The default value is 60 seconds.## It is important to make sure that this value is greater than the value# specified for repl-ping-slave-period otherwise a timeout will be detected# every time there is low traffic between the master and the slave.## repl-timeout 60# Disable TCP_NODELAY on the slave socket after SYNC?## If you select "yes" Redis will use a smaller number of TCP packets and# less bandwidth to send data to slaves. But this can add a delay for# the data to appear on the slave side, up to 40 milliseconds with# Linux kernels using a default configuration.## If you select "no" the delay for data to appear on the slave side will# be reduced but more bandwidth will be used for replication.## By default we optimize for low latency, but in very high traffic conditions# or when the master and slaves are many hops away, turning this to "yes" may# be a good idea.repl-disable-tcp-nodelay no# The slave priority is an integer number published by Redis in the INFO output.# It is used by Redis Sentinel in order to select a slave to promote into a# master if the master is no longer working correctly.# A slave with a low priority number is considered better for promotion, so# for instance if there are three slaves with priority 10, 100, 25 Sentinel will# pick the one wtih priority 10, that is the lowest.## However a special priority of 0 marks the slave as not able to perform the# role of master, so a slave with priority of 0 will never be selected by# Redis Sentinel for promotion.## By default the priority is 100.slave-priority 100 #如果master不能再正常工作，那麼會在多個slave中，選擇優先值最小的一個slave提升為master，優先值為0表示不能提升為master

看了上面的預設配置，其實也很容易理解，修改下就可以配置主從複製了，有 slaveof <masterip> <masterport> ，就成了從伺服器 ，沒有就是主伺服器

主伺服器，從伺服器，配置一樣，只不過 修改/etc/redis.conf 中 

slaveof 192.168.1.33 6379

然後開啟從伺服器的redis服務。

測試

#主伺服器redis-cli -p 6379 set hello world#從伺服器redis-cli -p 6379 get hello"world"#主伺服器redis-cli -p 6379 set hello world2#從伺服器redis-cli -p 6379 get hello"world2"redis-cli -p 6379 set hello world(error) READONLY You can‘t write against a read only slave.#成功 配置主從redis 伺服器。好簡單啊。

由於配置中有一條 從伺服器 是唯讀，所以從伺服器 沒法設定資料，只可以讀取資料

redis主從複製