Redis cluster

principle

1. be-all redis Nodes interconnect with each other (PING-PONG Mechanism )(ping For similar requests ,pong Just like the response ), Internally, binary protocols are used to optimize transmission speed and bandwidth .

2. Node fail It only takes effect when more than half of the nodes in the cluster are detected to have failed .

3. The client and redis Node is directly connected , You don't need the middle proxy layer . The client does not need to connect to all the nodes of the cluster , Connect to any of the available nodes in the cluster

4. redis-cluster Map all the physical nodes to [0-16383]slot On ,cluster Responsible for maintaining node<->slot（ Slot ）<->value
   Redis There's a built-in... In the cluster 16384 Hash slot , When need is in Redis Place one in the cluster key-value when ,redis First pair key Use crc16 The algorithm works out a result , Then get the result right 16384 Mod , So each of them key They all have a number in 0-16383 The Hashi trough between ,redis The hash slot will be mapped to different nodes approximately equally according to the number of nodes .

5. redis The benefits of clustering ： Distribute the data on different nodes , Reduce the throughput of a single node , So as to improve the performance of a single node .

Vote

1. The voting process is all in the cluster master Participate in (slave It's a backup , Not working , Only when the host is down , The slave of the host will be enabled ), If more than half master Node and master Node communication timeout (cluster-node-timeout), Think of the current master Node down .
2. When is the entire cluster unavailable (cluster_state:fail)?
   • If the cluster is arbitrary master Hang up , And the current master No, slave. Cluster into fail state , It can also be understood as a cluster slot mapping [0-16383] Enter when not finished fail state .
     ps : redis-3.0.0.rc1 Join in cluster-require-full-coverage Parameters , Off by default , Failed to open the cluster compatibility section .
   • If more than half of the clusters master Hang up , Whether or not slave Cluster into fail state .
     ps: When the cluster is not available , All operations on the cluster are not available , received ((error) CLUSTERDOWN The cluster is down) error

build redis colony

Cluster setup environment preparation

#  install gcc Environmental Science （redis Use c Language development ）
yum -y install gcc gcc-c++

#  install ruby Environmental Science （redis Cluster dependency ruby）
yum -y install ruby rubygems
gem install redis-3.0.3.gem（ This needs to be downloaded by yourself ）（ amount to redis and ruby The interface of ）

# 1. Create a cluster Directory cluster-redis
# 2. stay cluster-redis establish 8 A catalog ： The directory name is ：7001-7008
# 3. Copy redis Stand alone service bin Directory to  7001  Catalog 
# 4. modify redis service （bin Catalog ）
	#  Modify port as 7001（ Consistent with the directory name ）
	#  Enable cluster configuration ：cluster-enable yes
	#  Empty redis service  aof,rdb  Persistent files , Keep cluster nodes clean 
#  Copy 7001 A single machine with a modified directory redis service --- To   other 7 A catalog 
#  Modify other 7 Ports of directories （ The port and directory name are the same ）