redis演练(8) redis Cluster 集群环境安装
redis是个分布式缓存，与传统数据库最大的优势，在于它的“分布式”上。分布式的优势：
[*] 容易实现容量的扩展
[*] 数据的均等分布
[*] 很好的高可用性
redis 和memcached是分布式缓存的两款流行方案，他们之间的对比
redismemcached主从功能 Replication 支持
主备自动切换
本身不支持，可以通过客户端自己实现键值一致性哈希槽一致性哈希集群服务端支持（但是beta版） unstable由客户端实现工具支持提供自带的工具（客户端redis-cli,check-rdb...）较弱数据存储支持不支持，重启数据丢失 本章主要内容
安装一个三主的redis集群环境。
准备
由于本人没有接触过ruby语言，在安装之前做功课时，需要安装ruby环境等，心理上有了点小负担，担心遇到麻烦。后来，不出所料遇到了点麻烦。最后，还是安装成功了，回头想想，没有什么可担心的，无外乎失败了重装，真是年纪越大，胆子越小啊。我采用的方式，“兵来将挡，水来土掩”，有错就解决错，一步步安装。借助网络的力量，逐个把问题击破。
安装ruby环境
1.安装ruby
遇到的问题
未安装ruby
版本过低
未安装rubygem
gem源出错
请参考
http://blog.csdn.net/c77_cn/article/details/38227797
2. 编译redis cluster
从https://github.com/antirez/redis/branches下载unstable版本。
编译
make
此时,在/usr/local/src/redis-unstable/src 目录下生成了支持cluster的redis-server 3.建立集群环境
1.建立目录
cp /usr/local/redis
mkdir cluster-test
cd cluster-test/
mkdir 7000
mkdir 7001
mkdir 7002
2.复制redis-server
cp /usr/local/src/redis-unstable/src/redis-server/usr/local/redis/cluster-test/7001
cp /usr/local/src/redis-unstable/src/redis-server/usr/local/redis/cluster-test/7000
cp /usr/local/src/redis-unstable/src/redis-server/usr/local/redis/cluster-test/7002
#集群管理工具（为了方便，将他复制到合适位置）
cp /usr/local/src/redis-unstable/src/redis-trib.rb /usr/local/redis/cluster-test
3.建立3个cluster 节点对应的redis.conf文件
# vi 7000/redis.conf
port 7000
cluster-enabled yes
cluster-config-file nodes.conf
cluster-node-timeout 5000
appendonly yes
daemonize yes
logfile "redis7000.log"
#这是最简单的集群参数
其他7001/redis.conf,7002.conf文件， 仅仅port和logfile参数不同，其他一样。
此时 7000, 7001,7002目录下，只有2个文件,分别是 redis-server,redis.conf
4. 启动（分别启动3个主节点）
cd 7000
./redis-server ./redis.conf
cd ../7001/
./redis-server ./redis.conf
cd ../7002
./redis-server ./redis.conf
对应某个节点日志
26361:M 10 Sep 21:13:22.054 * No cluster configuration found, I'm 7f242cf2c7ce5d84103638c5017f2204e1509f4c
_._
_.-``__ ''-._
_.-`` `.`_.''-._ Redis 3.2.3 (00000000/0) 32 bit
.-`` .-```.```\/ _.,_ ''-._
( ' , .-`| `, ) Running in cluster mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 7001
| `-._ `._ / _.-' | PID: 26361
`-._ `-._`-./_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
26361:M 10 Sep 21:13:22.075 # Server started, Redis version 3.2.3
26361:M 10 Sep 21:13:22.075 * DB loaded from append only file: 0.000 seconds
26361:M 10 Sep 21:13:22.076 # I have keys for unassigned slot 5659. Taking responsibility for it.
26361:M 10 Sep 21:13:22.076 # I have keys for unassigned slot 9980. Taking responsibility for it.
26361:M 10 Sep 21:13:22.080 * The server is now ready to accept connections on port 7001
5. 建立集群
./redis-trib.rb create127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 # ./redis-trib.rb create127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002
>>> Creating cluster
>>> Performing hash slots allocation on 3 nodes...
Using 3 masters:
127.0.0.1:7000
127.0.0.1:7001
127.0.0.1:7002
M: 5ad201ebdf0553690295dcd06f89f15750e73989 127.0.0.1:7000
slots:0-5460 (5461 slots) master
M: 7f242cf2c7ce5d84103638c5017f2204e1509f4c 127.0.0.1:7001
slots:5461-10922 (5462 slots) master
M: 8ea7b0976e4848653435e4e77af311a6ade330a8 127.0.0.1:7002
slots:10923-16383 (5461 slots) master
Can I set the above configuration? (type 'yes' to accept): yes
>>> Nodes configuration updated
>>> Assign a different config epoch to each node
>>> Sending CLUSTER MEET messages to join the cluster
Waiting for the cluster to join.
>>> Performing Cluster Check (using node 127.0.0.1:7000)
M: 5ad201ebdf0553690295dcd06f89f15750e73989 127.0.0.1:7000
slots:0-5460 (5461 slots) master
0 additional replica(s)
M: 8ea7b0976e4848653435e4e77af311a6ade330a8 127.0.0.1:7002
slots:10923-16383 (5461 slots) master
0 additional replica(s)
M: 7f242cf2c7ce5d84103638c5017f2204e1509f4c 127.0.0.1:7001
slots:5461-10922 (5462 slots) master
0 additional replica(s)
All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
All 16384 slots covered.
这时候主节点日志
26536:M 10 Sep 21:25:32.360 * DB loaded from append only file: 0.000 seconds
26536:M 10 Sep 21:25:32.361 * The server is now ready to accept connections on port 7000
26536:M 10 Sep 21:27:54.651 # configEpoch set to 1 via CLUSTER SET-CONFIG-EPOCH
26536:M 10 Sep 21:27:54.660 # IP address for this node updated to 127.0.0.1
26536:M 10 Sep 21:27:59.619 # Cluster state changed: ok
6.测试
#/usr/local/redis/bin/redis-cli-c -p 7000
127.0.0.1:7000> keys *
(empty list or set)
127.0.0.1:7000> set title "cluster1"
OK
127.0.0.1:7000> set title1 "cluster1"
OK
127.0.0.1:7000> set title2 "cluster1"
-> Redirected to slot located at 127.0.0.1:7002
OK
127.0.0.1:7002> set title5 "cluster4"
-> Redirected to slot located at 127.0.0.1:7000
OK
127.0.0.1:7000> set title3 "cluster4"
-> Redirected to slot located at 127.0.0.1:7001
OK
127.0.0.1:7001> get title
-> Redirected to slot located at 127.0.0.1:7000
"cluster1"
127.0.0.1:7000> get title2
-> Redirected to slot located at 127.0.0.1:7002
"cluster8111"
127.0.0.1:7002> get title3
-> Redirected to slot located at 127.0.0.1:7001
"cluster4"
#节点间来回重定向
到了这里，环境算是搭建好了。当然，这是最简单的集群了。以后随着演练的深入，也会对集群进行深入探讨。
遇到问题
可能遇到的错误（是第二次建立集群时报错）
ERR Slot 2217 is already busy (Redis::CommandError)
解决方法： (in all nodes did FLUSHALL and then CLUSTER RESET SOFT)
Either the node already knows other nodes
# ./redis-trib.rb create127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002
>>> Creating cluster
Node 127.0.0.1:7000 is not empty. Either the node already knows other nodes (check with CLUSTER NODES) or contains some key in database 0.
解决方法：这是因为重复设置集群。
重启集群，发现数据丢失
集群创建完成后，当关机或者关闭集群再次启动的时候，一定要在node-conf所在的目录启动各个节点，
集群才能正常连接。
参考资源
http://blog.csdn.net/c77_cn/article/details/38227797
http://redis.io/topics/cluster-tutorial
http://redisdoc.com/topic/cluster-tutorial.html
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