Redis master-slave replication, sentinel mode and cluster

Catalog

One 、Redis Master-slave replication of

1、 Overview of master-slave replication

2、 Redis The role of master-slave replication

3、 Redis Master slave replication process

4、Redis The construction of master and slave

Two 、Redis Sentry mode

1、 The principle of sentinel mode

2、 The role of sentinel mode

3、 The construction of sentry mode

3、 ... and 、Redis The cluster of

1、 The role of clusters

2、 Fragmented data in cluster mode

3、 Cluster deployment

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One 、Redis Master-slave replication of

1、 Overview of master-slave replication

Master slave copy , It means to put one Redis Server data , Copy to other Redis The server . The former is called the main node (Master), The latter is called the slave node (Slave); Data replication is one-way , From master to slave only .

By default , Each station Redis Servers are all primary nodes ; And a master node can have multiple slave nodes ( Or no slave ), But a slave node can only have one master node .

2、Redis The role of master-slave replication

（1） data redundancy

Master-slave replication realizes hot backup of data , It's a way of data redundancy beyond persistence .

（2） Troubleshooting

When there is a problem with the master node , Can be served by a slave node , Fast fault recovery ; It's actually a redundancy of services .

（3） Load balancing

On the basis of master-slave replication , Cooperate with the separation of reading and writing , Write service can be provided by the master node , Read service provided by slave node ( The write Redis Connect master node when data is applied , read Redis Apply connection from node when data ), Share server load ; Especially in the situation of less writing and more reading , Sharing read load through multiple slave nodes , Can be greatly improved Redis Concurrency of servers .

（4） High availability cornerstone

In addition to the above functions , Master slave replication is also the foundation for sentinels and clusters to implement , So master-slave replication is Redis High availability Foundation .

3、Redis Master slave replication process

（1） If you start a Slave Machine processes , Then it will go to Master The machine sends a message “sync command" command , Request synchronous connection .
（2） Whether it's the first connection or reconnection ,Master machine Will start a background process , Save data snapshot to data file ( perform rdb operation ) , meanwhile Master All commands to modify data are also recorded and cached in the data file .
（3） After the background process completes the cache operation ,Master The machine will turn to Slave The machine sends data files ,Slave The end machine saves the data file to the hard disk , Then load it into memory , next Master The machine will send all operations to modify the data to Slave End machine . if Slave Failure causes downtime , It will automatically reconnect after returning to normal .
（4）Master The machine received Slave After the connection of the end machine , Send its complete data file to Slave End machine , If Mater Receive multiple at the same time Slave Synchronization request from , be Master A process will be started in the background to save the data file , Then send it to all Slave End machine , Ensure that all Slave The end machine is normal .

4、Redis The master-slave structure

（1） Environment building

1、master node

ip Address ：192.168.222.10    redis-5.0.7.tar. gz

2、slave1

ip Address ：192.168.222.100  redis-5.0.7.tar. gz

3、slave 2

ip Address ：192.168.222.20     redis-5.0.7.tar. gz

（2） install redis

Use the one click deployment script

#!/bin/bash
# install redis
read -p " Please enter the local IP Address :" ip

systemctl stop firewalld
setenforce 0

# install gcc gcc-c++  compiler 
yum install -y gcc gcc-c++ make &> /dev/null
if [ $? -eq 0 ];then
echo -e  "\033[34;1m  Compiler installation complete ！ \033[0m"
fi

# take redis-5.0.7.tar.gz Upload the compressed package to /opt Directory , decompression , And compile and install 
cd /opt
tar zxvf redis-5.0.7.tar.gz -C /opt/ &> /dev/null
cd /opt/redis-5.0.7/
make &> /dev/null
make PREFIX=/usr/local/redis install &> /dev/null
if [ $? -eq 0 ];then
echo -e  "\033[34;1m redis Compile and install complete ！ \033[0m"
fi

# Execute the... Provided by the software package installserver.sh Script file settings Redis Relevant configuration files required by the service 
yum -y install expect &> /dev/null
/usr/bin/expect <<EOF
cd /opt/redis-5.0.7/utils
spawn /opt/redis-5.0.7/utils/install_server.sh
expect "instance:" {send "\r"}
expect "/etc/redis/6379.conf" {send "\r"}
expect "/var/log/redis_6379.log" {send "\r"}
expect "/var/lib/redis/6379" {send "\r"}
expect "path" {send "/usr/local/redis/bin/redis-server\r"}
expect "ENTER" {send "\r"}
expect eof
EOF
if [ $? -eq 0 ];then
echo -e  "\033[34;1m redis Configuration complete ！ \033[0m"
fi

# hold redis The executable program file of is put into the directory of path environment variable to facilitate system identification 
ln -s /usr/local/redis/bin/* /usr/local/bin/
netstat -natp | grep redis

# Redis Service control 

/etc/init.d/redis_6379 start
/etc/init.d/redis_6379 status

# Modify the configuration /etc/redis/6379.conf Parameters 
sed -i '70s/bind 127.0.0.1/bind '$ip'/' /etc/redis/6379.conf
sed -i 's/appendonly no/appendonly yes/' /etc/redis/6379.conf
/etc/init.d/redis_6379 restart
if [ $? -eq 0 ];then
echo -e  "\033[34;1m redis installation is complete ！ \033[0m"
fi
netstat -natp | grep redis

（3） modify Master Node profile （192.168.222.10）

（1）# modify master Master profile 
vim /etc/redis/6379.conf
bind 192.168.222.10      			   #70 That's ok , Comment out bind term , Or modify to 192.168.222.10, network card 
daemonize yes         			   #137 That's ok , Start Daemons 
logfile /var/log/redis_6379.log    #172 That's ok , Specify the log file directory 
dir /var/lib/redis/6379            #264 That's ok , assign work directory 
appendonly yes       			   #700 That's ok , Turn on AOF Persistence function 

（2）# restart redis
/etc/init.d/redis_6379 restart

 （3） modify Slave Node profile

（1）# modify slave1 node 、slave2 Node profile ,slave1 and slave2 The modification steps are the same 
vim /etc/redis/6379.conf
bind 0.0.0.0      				     #70 That's ok , Modify the listening address 
daemonize yes       				 #137 That's ok , Start Daemons 
logfile /var/log/redis_6379.log      #172 That's ok , Specify the log file directory 
dir /var/lib/redis/6379              #264 That's ok , assign work directory 
replicaof 192.168.222.10 6379         #287 That's ok , Uncomment and specify the to synchronize Master node IP And port 
appendonly yes       				 #700 That's ok , Turn on AOF Persistence function 

（2）# restart slave1 Nodes and slave2 node redis service 
/etc/init.d/redis_6379 restart

 

 slave2 ditto

（4） Verify the master-slave effect

 stay Master View the log on the node 

tail -f /var/log/redis_6379.log 

 stay Master Verify the slave node on the node 
[[email protected] ~]# redis-cli info replication
# Replication
role:master
connected_slaves:2
slave0:ip=192.168.222.100,port=6379,state=online,offset=84,lag=1
slave1:ip=192.168.222.20,port=6379,state=online,offset=84,lag=1
master_replid:fa5e578f6ee562d98eb5bf4b9f2dcc8868b90231
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:84
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:84

Two 、Redis Sentry mode

1、 The principle of sentinel mode

  sentry (sentinel)： It's a distributed system , It is used to monitor each server in the master-slave structure , When there is a failure, the voting mechanism is used to select a new one Master And put all Slave Connect to the new Master. Therefore, the number of clusters running sentinels should not be less than 3 Nodes .

2、 The role of sentinel mode

（1） monitor ： The Sentry will constantly check whether the master and slave nodes are working properly .

（2） Automatic failover ： When the master node is not working properly , Sentinels will start automatic failover operations , It will upgrade one of the failed master nodes from a node to a new master , And let the other slave node copy the new master node .

（3） notice （ remind ）： Sentinels can send failover results to clients .

3、 The construction of sentry mode

（1） modify Redis The configuration file （ All node operations ）

vim /opt/redis-5.0.7/sentinel.conf
protected-mode no								#17 That's ok , Turn off protection mode 
port 26379										#21 That's ok ,Redis Sentry's default listening port 
daemonize yes									#26 That's ok , Appoint sentinel Start for background 
logfile "/var/log/sentinel.log"					#36 That's ok , Specify the log storage path 
dir "/var/lib/redis/6379"						#65 That's ok , Specify the database storage path 
sentinel monitor mymaster 192.168.222.10 6379 2	#84 That's ok , modify   Specify the sentinel node to monitor 192.168.222.10:6379 This master node , The name of the master node is mymaster, final 2 The meaning of is related to the fault determination of the master node ： Need at least 2 Sentinel nodes agree , To determine the failure of the primary node and carry out failover 
sentinel down-after-milliseconds mymaster 30000	#113 That's ok , Decision server down Lost time period , Default 30000 millisecond （30 second ）
sentinel failover-timeout mymaster 180000		#146 That's ok , The maximum timeout of the failed node is 180000（180 second ）

 （2） Start sentinel mode

cd /opt/redis-5.0.7/
redis-sentinel sentinel.conf &
 Be careful ！ Start the main server first , Then start the slave server 

（3）  fault simulation

see redis-server Process number

[[email protected] redis-5.0.7]# ps aux | grep redis
root       8781  0.1  0.2 162548  9880 ?        Ssl  21:19   0:05 /usr/local/redis/bin/redis-server 0.0.0.0:6379
root      11500  0.2  0.2 153844  7944 ?        Ssl  22:25   0:00 redis-sentinel *:26379 [sentinel]
root      11530  0.0  0.0 112676   984 pts/1    R+   22:29   0:00 grep --color=auto redis

  Kill Master Node redis-server The process number of

kill -9 8781

 （4） The verification results

Dynamically view sentinel log results

tail -f /var/log/sentinel.log

redis-cli -p 26379 INFO Sentinel

3、 ... and 、Redis colony

1、 The role of clusters

（1） Data partition

Data partition ( Or data fragmentation ) It is the core function of cluster .

Clusters spread data across multiple nodes , On the one hand, it has broken through Redis The limit of single machine memory size , There's a huge increase in storage capacity ; On the other hand, each master node can provide external reading and writing services , It greatly improves the response ability of the cluster .
Redis The size of single machine memory is limited , Both persistence and master-slave replication are mentioned ; for example , If the single machine memory is too large ,bgsave and bgrewriteaof Of fork Operation may cause the main process to block , When the host is switched in the master-slave environment, the slave node may be unable to provide services for a long time , During the full replication phase, the replication buffer of the master node may overflow .

（2） High availability

Cluster supports master-slave replication and automatic fail over of master nodes （ Like a sentry ）; When any node fails , Clusters can still provide external services .

2、Redis Data fragmentation of cluster

Redis Cluster introduces the concept of hash slot
Redis Cluster has 16384 Hash slot （ Number 0-16383）
Each node of the cluster is responsible for a portion of the hash slot
Every Key adopt CRC16 Check pair 16384 Take the rest to decide which Hashi slot to place , By this value , Go to find the node corresponding to the corresponding slot , Then directly and automatically jump to the corresponding node for access operation

# With 3 Take a cluster of nodes as an example ：
node A contain 0 To 5460 Hash slot
node B contain 5461 To 10922 Hash slot
node C contain 10923 To 16383 Hash slot

#Redis The master-slave replication model of the cluster
There are A、B、C Three nodes , If node B failed , The whole cluster will be short of 5461-10922 This range of slots can not be used .
Add a slave node for each node A1、B1、C1 The whole cluster has three Master Nodes and three slave Node composition , At the node B After failure , A cluster election B1 The master node with bit continues to serve . When B and B1 After failure , The cluster will not be available
 

3、 Cluster deployment

（1） Environment building

master 1

192.168.222.10    redis-5.0.7.tar.gz

slave1

192.168.222.100   redis-5.0.7.tar.gz

master 2

192.168.222.20      redis-5.0.7.tar.gz

slave 2                   

192.168.222.30      redis-5.0.7.tar.gz

master 3

192.168.222.40      redis-5.0.7.tar.gz

slave   3

192.168.222.50      redis-5.0.7.tar.gz

（2） All nodes

cd /etc/redis/
mkdir -p redis-cluster/redis6379
cp /opt/redis-5.0.7/redis.conf /etc/redis/redis-cluster/redis6379/
cp /opt/redis-5.0.7/src/redis-cli /opt/redis-5.0.7/src/redis-server /etc/redis/redis-cluster/redis6379/

 （3）master1 node

# other 5 The configuration files of folders are modified, and so on , Be careful 6 Each port is different .
cd /etc/redis/redis-cluster/redis6379
vim redis.conf

bind 192.168.222.10					#69 That's ok , modify bind term , Monitor your own IP
protected-mode no						#88 That's ok , modify , Turn off protection mode 
port 7001								#92 That's ok , modify ,redis Listening port ,
daemonize yes							#136 That's ok , Start as a separate process 
cluster-enabled yes						#832 That's ok , uncomment , Turn on the cluster function 
cluster-config-file nodes-6379.conf		#840 That's ok , uncomment , Cluster name file settings , There is no need to modify 
cluster-node-timeout 15000				#846 That's ok , Uncomment cluster timeout setting 
appendonly yes							#699 That's ok , modify , Turn on AOF Persistence 

 

scp /etc/redis/redis-cluster/redis6379/redis.conf [email protected]:/etc/redis/redis-cluster/redis6379/redis.conf
scp /etc/redis/redis-cluster/redis6379/redis.conf [email protected]:/etc/redis/redis-cluster/redis6379/redis.conf
scp /etc/redis/redis-cluster/redis6379/redis.conf [email protected]:/etc/redis/redis-cluster/redis6379/redis.conf
scp /etc/redis/redis-cluster/redis6379/redis.conf [email protected]:/etc/redis/redis-cluster/redis6379/redis.conf
scp /etc/redis/redis-cluster/redis6379/redis.conf [email protected]:/etc/redis/redis-cluster/redis6379/redis.conf

 （4） The rest of the nodes

vim /etc/redis/redis-cluster/redis6379/redis.conf

69 Line modify native ip Address 
92 No. modify the port number 

 

（5） Start cluster

 All nodes 
cd /etc/redis/redis-cluster/redis6379/
redis-server redis.conf

redis-cli --cluster create 192.168.222.10:7001 192.168.222.20:7003 192.168.222.40:7005 192.168.222.50:7006 192.168.222.30:7004 192.168.222.100:7002 --cluster-replicas 1

redis-cli -h 192.168.222.10 -p 7001 -c        # Add -c Parameters , Nodes can jump to each other 	
cluster slots			# View the hash slot number range of the node 
set sky blue
cluster keyslot sky	# see name Key slot number