[redis] redis

redis是什么？

wiki

redis官方介绍：introduction to redis

安装：

install 拉到最下面的install小节

wget http://download.redis.io/releases/redis-4.0.11.tar.gz
tar zxvf redis-4.0..tar.gz
cd redis-4.0.
make

运行：

[root@T9 redis-4.0.]# ./src/redis-server
:C  Oct ::21.602 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
:C  Oct ::21.602 # Redis version=4.0., bits=, commit=, modified=, pid=, just started
:C  Oct ::21.602 # Warning: no config file specified, using the default config. In order to specify a config file use ./src/redis-server /path/to/redis.conf
:M  Oct ::21.603 * Increased maximum number of open files to  (it was originally set to ).
                _._
           _.-``__ ''-._
      _.-``    `.  `_.  ''-._           Redis 4.0. (/)  bit
  .-`` .-```.  ```\/    _.,_ ''-._
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port:
 |    `-._   `._    /     _.-'    |     PID: 14015
  `-._    `-._  `-./  _.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |           http://redis.io
  `-._    `-._`-.__.-'_.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |
  `-._    `-._`-.__.-'_.-'    _.-'
      `-._    `-.__.-'    _.-'
          `-._        _.-'
              `-.__.-'                                               

:M  Oct ::21.603 # WARNING: The TCP backlog setting of  cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of .
:M  Oct ::21.603 # Server initialized
:M  Oct ::21.603 # WARNING overcommit_memory is set to ! 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.
:M  Oct ::21.603 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
:M  Oct ::21.604 * Ready to accept connections

测试：

[root@T9 redis-4.0.]# ./src/redis-cli
127.0.0.1:> set foo bar
OK
127.0.0.1:> get foo
"bar"
127.0.0.1:> get bar
(nil)
127.0.0.1:> 

tutorial

<<The Little Redis Book>>

The book is many years old, but still relevant. Redis has evolved a lot, but most of that has been in the form of internal improvements,
new advanced features (like lua scripting) and awesome new data types. The best way to learn Redis is still to start by understanding
the fundamentals presented in this book.

读书笔记：

[redis] <<The little Redis book>>的读书笔记

其他内容摘要

在cli上查看server状态

127.0.0.1:> info
# Server
redis_version:4.0.
redis_git_sha1:
redis_git_dirty:
。。。 

摘录：

# 传统关系型数据库，用表，表示一切。
If we were to apply this data structure concept to the relational world, we could say that databases expose a single
data structure - tables. 
# redis，用五种基本数据结构。
To me, that defines Redis’ approach. If you are dealing with scalars, lists,
hashes, or sets, why not store them as scalars, lists, hashes and sets? 

概念

数据库

用数字代表，默认是0。用select命令切换。如下：

127.0.0.1:> select
OK
127.0.0.1:[]> select
OK
127.0.0.1:> 

关于K-V

While Redis is more than just a key-value store, at its core, every one of Redis’ five data structures has at least a
key and a value. 

全部redis命令的详细列表

https://redis.io/commands

redis cluster的文档

HA：https://redis.io/topics/sentinel

https://redis.io/topics/cluster-tutorial

https://redis.io/topics/cluster-spec

创建redis cluster

1. 创建配置文件

[root@T9 cluster]# pwd
/root/worklist/-redis/cluster
[root@T9 cluster]# cat redis.conf
port
cluster-enabled yes
cluster-config-file nodes.conf
cluster-node-timeout
appendonly yes
[root@T9 cluster]# 

2. 为6个实例创建配置文件

[root@T9 cluster]# tree
.
├──
│   └── redis.conf
├──
│   └── redis.conf
├──
│   └── redis.conf
├──
│   └── redis.conf
├──
│   └── redis.conf
├──
│   └── redis.conf

3. 分别启动6个实例

[root@T9 7000]# ../../redis-4.0.11/src/redis-server ./redis.conf

4. 创建

[root@T9 redis-4.0.11]# ./src/redis-cli --cluster create 127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 127.0.0.1:7003 127.0.0.1:7004 127.0.0.1:7005 --cluster-replicas 1
Unrecognized option or bad number of args for: '--cluster'
[root@T9 redis-4.0.11]# 

创建没成功。 redis-cli不支持这个命令了，可能。

看了create-cluster脚本，里边是这样的：

[root@T9 redis-4.0.11]# ./src/redis-trib.rb create --replicas 1 127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 127.0.0.1:7003 127.0.0.1:7004 127.0.0.1:7005

在此之前，还需要安装：

yum install ruby
yum install rubygem-redis

上边的命令在5.0里也旧了。最新的写法是这样的（所以上边那两个ruby，其实也可以不装）：

redis-cli --cluster create \
>         192.168.2.205: 192.168.2.205: 192.168.2.205: 192.168.2.205: 192.168.2.205: 192.168.2.205: \
>         --cluster-replicas 

成功之后，master大概会打印这些东西：

:M  Oct ::32.268 # configEpoch set to  via CLUSTER SET-CONFIG-EPOCH
:M  Oct ::32.284 # IP address for this node updated to 127.0.0.1
:M  Oct ::37.224 # Cluster state changed: ok
:M  Oct ::37.551 * Slave 127.0.0.1: asks for synchronization
:M  Oct ::37.551 * Partial resynchronization not accepted: Replication ID mismatch (Slave asked for '333d735fee630925f6cb26009980da7c036c1be1', my replication IDs are '0afc41e9ed8a0e316dbca9051ffa1c4bdcbab8dd' and '')
:M  Oct ::37.551 * Starting BGSAVE for SYNC with target: disk
:M  Oct ::37.553 * Background saving started by pid
:C  Oct ::37.899 * DB saved on disk
:C  Oct ::37.902 * RDB:  MB of memory used by copy-on-write
:M  Oct ::37.980 * Background saving terminated with success
:M  Oct ::37.981 * Synchronization with slave 127.0.0.1: succeeded

slave会打印这些：

:M  Oct ::32.269 # configEpoch set to  via CLUSTER SET-CONFIG-EPOCH
:M  Oct ::32.292 # IP address for this node updated to 127.0.0.1
:S  Oct ::36.989 * Before turning into a slave, using my master parameters to synthesize a cached master: I may be able to synchronize with the new master with just a partial transfer.
:S  Oct ::36.989 # Cluster state changed: ok
:S  Oct ::37.548 * Connecting to MASTER 127.0.0.1:
:S  Oct ::37.548 * MASTER <-> SLAVE sync started
:S  Oct ::37.548 * Non blocking connect for SYNC fired the event.
:S  Oct ::37.549 * Master replied to PING, replication can continue...
:S  Oct ::37.550 * Trying a partial resynchronization (request 333d735fee630925f6cb26009980da7c036c1be1:).
:S  Oct ::37.900 * Full resync from master: 28607c280e263eaefb803cc88f213822187e903f:
:S  Oct ::37.900 * Discarding previously cached master state.
:S  Oct ::37.981 * MASTER <-> SLAVE sync: receiving  bytes from master
:S  Oct ::37.982 * MASTER <-> SLAVE sync: Flushing old data
:S  Oct ::38.008 * MASTER <-> SLAVE sync: Loading DB in memory
:S  Oct ::38.008 * MASTER <-> SLAVE sync: Finished with success
:S  Oct ::38.012 * Background append only file rewriting started by pid
:S  Oct ::38.302 * AOF rewrite child asks to stop sending diffs.
:C  Oct ::38.302 * Parent agreed to stop sending diffs. Finalizing AOF...
:C  Oct ::38.302 * Concatenating 0.00 MB of AOF diff received from parent.
:C  Oct ::38.303 * SYNC append only file rewrite performed
:C  Oct ::38.304 * AOF rewrite:  MB of memory used by copy-on-write
:S  Oct ::38.330 * Background AOF rewrite terminated with success
:S  Oct ::38.330 * Residual parent diff successfully flushed to the rewritten AOF (0.00 MB)
:S  Oct ::38.331 * Background AOF rewrite finished successfully

脚本最后会打印这个：

[OK] All  slots covered

杀掉一个master

它的slave会升成master

:S  Oct ::11.497 # Error condition on socket for SYNC: Connection refused
:S  Oct ::11.604 # Failover election won: I'm the new master.
:S  Oct ::11.605 # configEpoch set to  after successful failover
:M  Oct ::11.605 # Setting secondary replication ID to a7bc292355042d4c2344f8a84503a418775018f0, valid up to offset: . New replication ID is 1ac1b3a40de43eb7012840543e9e50200a948334
:M  Oct ::11.605 * Discarding previously cached master state.
:M  Oct ::11.605 # Cluster state changed: ok

再启动这个master，它会变成slave

再杀掉新的master，slave又会变回成master。

5. shutdown

[root@T9 redis-4.0.]# ./src/redis-cli -p  shutdown nosave
[root@T9 redis-4.0.]# ./src/redis-cli -p  shutdown nosave
[root@T9 redis-4.0.]# ./src/redis-cli -p  shutdown nosave
[root@T9 redis-4.0.]# ./src/redis-cli -p  shutdown nosave
[root@T9 redis-4.0.]# ./src/redis-cli -p  shutdown nosave
[root@T9 redis-4.0.]# ./src/redis-cli -p  shutdown nosave

使用脚本创建 redis cluster

脚本：

utils/create-cluster/create-cluster

启动：

[root@T9 create-cluster]# ./create-cluster start
[root@T9 create-cluster]# ./create-cluster create
[root@T9 create-cluster]# ./create-cluster stop

使用：与非cluster的区别是使用-c参数。

[root@T9 create-cluster]# ../../src/redis-cli -c -p 

gossip协议

https://www.jianshu.com/p/133560ef28df

其他

为什么redis cluster最小需要6个node？

redis cluster tutorial中写道：

Note that the minimal cluster that works as expected requires to contain at least three master nodes. For your first tests it is strongly suggested to start a six nodes cluster with three masters and three slaves.

用四个节点（2 master，2 slave）测试失败，错误信息如下：

[root@T9 -redis]# ./redis-4.0./src/redis-trib.rb create --replicas  127.0.0.1: 127.0.0.1: 127.0.0.1: 127.0.0.1:
>>> Creating cluster
*** ERROR: Invalid configuration for cluster creation.
*** Redis Cluster requires at least  master nodes.
*** This is not possible with  nodes and  replicas per node.
*** At least  nodes are required.
[root@T9 -redis]# 

可能是为了防止脑裂吧？  https://grokbase.com/t/gg/redis-db/15cbatbypm/why-a-minimal-cluster-should-require-at-least-three-master-nodes

用sentinel也是同理最少需要三个。

在sentinel文档里看见的一句话，应该是可以简单的解释了这个问题：

Note that we will never show setups where just two Sentinels are used, since Sentinels always need to talk with the majority in order to start a failover.

另外，redis部署了集群的话，就不需要部署哨兵了。

Cluster is only for when you need sharding.
If you only want replication + failover use Sentinel (though you still
need  hosts for the Sentinels)