Redis安装及主从配置

Redis是一种面向“键/值”对类型数据的分布式NoSQL数据库系统，特点是高性能，持久存储，适应高并发的应用场景。它起步较晚，发展迅速，目前已被许多大型机构采用，如google、taobao、sina微博等。本文不对其数据结构做深入的讲解，只是介绍其安装及主从结构的配置过程。如需要更详细的了解请参考其官方网站。

Redis的安装

Redis目前只支持Linux及BSD等系统，不支持Window下的安装。在Linux下安装的过程如下所示：

$ wget http://redis.googlecode.com/files/redis-2.2.12.tar.gz$ tar xzf redis-2.2.12.tar.gz$ cd redis-2.2.12$ make

安装成功后的提示为：

Hint: To run "make test" is a good idea ;）make[1]: Leaving directory `/usr/alibaba/install/redis-2.2.12/src"

在安装完成后，即可进入至该工程的src下启动服务：

$ src/redis-server

通过内置的build-cli工具进行相应的测试，其测试过程如下：

$ src/redis-cliredis> set foo barOKredis> get foo"bar"redis > getset foo 123“bar”redis >get foo123

Redis的主从配置

机器的分配

主从结构的配置所涉及到的机器及各机器所完成的功能如下所示：

IP地址	角色
10.20.150.205	主结点
10.20.150.208	从结点1
10.20.150.209	从结点2

主从结构的配置

在进行主从结构配置之前，请确保已经在上述三台机器上已经安装了Redis服务。对于Redis的主从结构的配置相对比较简单，只需修改redis.conf文件，配置上主结点对应的IP及端口。具体如下所示：

Port 6380bind 10.20.150.205slaveof 10.20.150.205 6379

l port 6380表示当前该Redis服务对应的端口号；l bind 10.20.150.205 表示当前Redis绑定的主结点的IP地址；l slaveof 10.20.150.205 6379 表示当前Redis是哪个主结点的从结点，其中包括IP及端口号。

当主结点在启动时

当只有一台主结点在启动时，会显示如下的信息：

[29028] 26 Sep 18:39:12 * Server started, Redis version 2.2.12[29028] 26 Sep 18:39:12 # WARNING overcommit_memory is set to 0！ Background save may fail under low memory condition. To fix this issue add "vm.overcommit_memory = 1" to /etc/sysctl.conf and then reboot or run the command "sysctl vm.overcommit_memory=1" for this to take effect.[29028] 26 Sep 18:39:12 * DB loaded from disk: 0 seconds[29028] 26 Sep 18:39:12 * The server is now ready to accept connections on port 6379[29028] 26 Sep 18:39:12 - 0 clients connected （0 slaves）, 790584 bytes in use

当有一台从结点10.20.150.208启动时

其中主结点会自动检测到有新的从结点启动并加入进来，其显示的信息如下：

[29028] 26 Sep 18:40:31 - Accepted 10.20.150.208:44779[29028] 26 Sep 18:40:31 * Slave ask for synchronization[29028] 26 Sep 18:40:31 * Starting BGSAVE for SYNC[29028] 26 Sep 18:40:31 * Background saving started by pid 29091[29091] 26 Sep 18:40:31 * DB saved on disk[29028] 26 Sep 18:40:31 * Background saving terminated with success[29028] 26 Sep 18:40:31 * Synchronization with slave succeeded[29028] 26 Sep 18:40:32 - 0 clients connected （1 slaves）, 798752 bytes in use[29028] 26 Sep 18:40:37 - 0 clients connected （1 slaves）, 798752 bytes in use[29028] 26 Sep 18:40:42 - 0 clients connected （1 slaves）, 798752 bytes in use[29028] 26 Sep 18:40:47 - 0 clients connected （1 slaves）, 798752 bytes in use

对于从结点显示的信息如下：

#[597] 26 Sep 18:40:29 * Server started, Redis version 2.2.12[597] 26 Sep 18:40:29 # WARNING overcommit_memory is set to 0！ Background save may fail under low memory condition. To fix this issue add "vm.overcommit_memory = 1" to /etc/sysctl.conf and then reboot or run the command "sysctl vm.overcommit_memory=1" for this to take effect.[597] 26 Sep 18:40:29 * The server is now ready to accept connections on port 6379[597] 26 Sep 18:40:29 - 0 clients connected （0 slaves）, 790616 bytes in use[597] 26 Sep 18:40:29 * Connecting to MASTER...[597] 26 Sep 18:40:29 * MASTER <-> SLAVE sync started: SYNC sent[597] 26 Sep 18:40:29 * MASTER <-> SLAVE sync: receiving 10 bytes from master[597] 26 Sep 18:40:29 * MASTER <-> SLAVE sync: Loading DB in memory[597] 26 Sep 18:40:29 * MASTER <-> SLAVE sync: Finished with success[597] 26 Sep 18:40:34 - 1 clients connected （0 slaves）, 798744 bytes in use

当有另外一台从机10.20.150.209挂载时

当有另一台从机挂载至主机时，主机显示的信息如下：

[29028] 26 Sep 18:42:52 - 0 clients connected （1 slaves）, 798752 bytes in use[29028] 26 Sep 18:42:57 - 0 clients connected （1 slaves）, 798752 bytes in use[29028] 26 Sep 18:42:58 - Accepted 10.20.150.209:47650[29028] 26 Sep 18:42:58 * Slave ask for synchronization[29028] 26 Sep 18:42:58 * Starting BGSAVE for SYNC[29028] 26 Sep 18:42:58 * Background saving started by pid 29287[29287] 26 Sep 18:42:58 * DB saved on disk[29028] 26 Sep 18:42:59 * Background saving terminated with success[29028] 26 Sep 18:42:59 * Synchronization with slave succeeded[29028] 26 Sep 18:43:02 - 0 clients connected （2 slaves）, 806920 bytes in use

从另一台从机上可以看到的信息如下：

[Intranet root@xasc-150-209 /usr/alibaba/install/redis-2.2.12/src]#./redis-server ../redis.conf [15034] 26 Sep 18:42:56 * Server started, Redis version 2.2.12[15034] 26 Sep 18:42:56 # WARNING overcommit_memory is set to 0！ Background save may fail under low memory condition. To fix this issue add "vm.overcommit_memory = 1" to /etc/sysctl.conf and then reboot or run the command "sysctl vm.overcommit_memory=1" for this to take effect.[15034] 26 Sep 18:42:56 * The server is now ready to accept connections on port 6379[15034] 26 Sep 18:42:56 - 0 clients connected （0 slaves）, 790616 bytes in use[15034] 26 Sep 18:42:56 * Connecting to MASTER...[15034] 26 Sep 18:42:56 * MASTER <-> SLAVE sync started: SYNC sent[15034] 26 Sep 18:42:56 * MASTER <-> SLAVE sync: receiving 10 bytes from master[15034] 26 Sep 18:42:56 * MASTER <-> SLAVE sync: Loading DB in memory[15034] 26 Sep 18:42:56 * MASTER <-> SLAVE sync: Finished with success[15034] 26 Sep 18:43:01 - 1 clients connected （0 slaves）, 798744 bytes in use

当主结点宕掉时

当主结点突然间不可用，两台从机会由于找不到主结点而报错，信息如下：

[597] 26 Sep 18:46:09 * Connecting to MASTER...[597] 26 Sep 18:46:09 # Unable to connect to MASTER: Connection refused[597] 26 Sep 18:46:10 * Connecting to MASTER...[597] 26 Sep 18:46:10 # Unable to connect to MASTER: Connection refused[597] 26 Sep 18:46:11 * Connecting to MASTER...[597] 26 Sep 18:46:11 # Unable to connect to MASTER: Connection refused[597] 26 Sep 18:46:12 * Connecting to MASTER...[597] 26 Sep 18:46:12 # Unable to connect to MASTER: Connection refused[597] 26 Sep 18:46:13 * Connecting to MASTER...[597] 26 Sep 18:46:13 # Unable to connect to MASTER: Connection refused[597] 26 Sep 18:46:14 - 0 clients connected （0 slaves）, 790616 bytes in use

主结点在没有启动的情况下，从机先启动时

当主结点还没有启动时，从结点先启动，由于找不到对应主结点，会报如下的信息错误：

[Intranet root@xasc-150-208 /usr/alibaba/install/redis-2.2.12/src]#./redis-server ../redis.conf [1842] 26 Sep 18:48:50 * Server started, Redis version 2.2.12[1842] 26 Sep 18:48:50 # WARNING overcommit_memory is set to 0！ Background save may fail under low memory condition. To fix this issue add "vm.overcommit_memory = 1" to /etc/sysctl.conf and then reboot or run the command "sysctl vm.overcommit_memory=1" for this to take effect.[1842] 26 Sep 18:48:50 * DB loaded from disk: 0 seconds[1842] 26 Sep 18:48:50 * The server is now ready to accept connections on port 6379[1842] 26 Sep 18:48:50 - 0 clients connected （0 slaves）, 790616 bytes in use[1842] 26 Sep 18:48:50 * Connecting to MASTER...[1842] 26 Sep 18:48:50 # Unable to connect to MASTER: Connection refused[1842] 26 Sep 18:48:51 * Connecting to MASTER...[1842] 26 Sep 18:48:51 # Unable to connect to MASTER: Connection refused[1842] 26 Sep 18:48:52 * Connecting to MASTER...[1842] 26 Sep 18:48:52 # Unable to connect to MASTER: Connection refused[1842] 26 Sep 18:48:53 * Connecting to MASTER...[1842] 26 Sep 18:48:53 # Unable to connect to MASTER: Connection refused[1842] 26 Sep 18:48:54 * Connecting to MASTER...[1842] 26 Sep 18:48:54 # Unable to connect to MASTER: Connection refused[1842] 26 Sep 18:48:55 - 0 clients connected （0 slaves）, 790616 bytes in use

当有一台从机不可用时

当有一台从机变得不可用时，主机显示的信息如下：

32 - 1 clients connected （0 slaves）, 798744 bytes in use[16848] 26 Sep 18:50:37 - 1 clients connected （0 slaves）, 798744 bytes in use[16848] 26 Sep 18:50:42 - 1 clients connected （0 slaves）, 798744 bytes in use

当两台从机都宕掉时

当两台从机都变得不可用时，主机显示的信息如下：

[29736] 26 Sep 18:52:57 - Client closed connection[29736] 26 Sep 18:53:02 - 0 clients connected （0 slaves）, 790584 bytes in use[29736] 26 Sep 18:53:07 - 0 clients connected （0 slaves）, 790584 bytes in use

主从结构的测试

在主结点上执行写入

在主机上执行写入命令1

redis> set foo bar

在各个从机上会显示的信息如下：

[2528] 26 Sep 18:57:01 - DB 0: 1 keys （0 volatile） in 4 slots HT.[2528] 26 Sep 18:57:01 - 1 clients connected （0 slaves）, 798952 bytes in use[2528] 26 Sep 18:57:06 - DB 0: 1 keys （0 volatile） in 4 slots HT.[2528] 26 Sep 18:57:06 - 1 clients connected （0 slaves）, 798936 bytes in use

在主机上执行get foo命令，显示的信息如下：

redis 127.0.0.1:6379> get foo"bar"

在从机10.20.150.208上执行get foo命令，显示的信息如下：

redis 127.0.0.1:6379> get foo"bar"

同理，在从机10.20.150.209上执行get foo命令，显示的信息如下：

redis 127.0.0.1:6379> get foo"bar"

当有一台从机挂掉后，在主机上写入

当有一台从机（10.20.150.208）宕机，在主机上执行setfoo1写入命令。主机上执行get foo1时显示的信息如下：

redis 127.0.0.1:6379> get foo1"test"

另一台从机上执行getfoo1时显示的信息如下：

redis 127.0.0.1:6379> get foo1"test"

当把10.20.150.208从机启动起来时，执行getfoo1命令，显示的信息如下：

redis 127.0.0.1:6379> get foo1"test"

可见，即使当从机挂掉并再次启动时，仍会将主机做过的修改全部都同步至重启的从机上。

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