Redis sentinel mechanism

Learn before redis The master-slave mechanism of , among slave After the node goes down, you can find master Node synchronization data , that master How to deal with node downtime ？

One 、 The role and principle of sentinels

effect ：

 Master Condition monitoring ：

 

  primary Master New election after failure Master：

new Master He began to reign ：

  summary ：

 

  Two 、 The construction of sentry group

Here we build a three node Sentinel colony , To supervise the previous Redis Master-slave cluster ：

Three sentinel Example information of ：

 

1、 Create folder ：

#  Get into /tmp Catalog 
cd /tmp
#  Create directory 
mkdir s1 s2 s3

2、 stay s1 Create a directory sentinel.conf file , Add the following ：

port 27001
sentinel announce-ip 192.168.1.103
sentinel monitor mymaster 192.168.1.103 7001 2
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 60000
dir "/tmp/s1"

notes ：

3、 take s1/sentinel.conf File copy to s2、s3 In both directories （ stay /tmp Directory execute the following command ）：

#  Mode one ： Copy one by one 
cp s1/sentinel.conf s2
cp s1/sentinel.conf s3
#  Mode two ： Pipe combination command , One click Copy 
echo s2 s3 | xargs -t -n 1 cp s1/sentinel.conf

  modify s2、s3 Configuration files in two folders , Change the ports to 27002、27003：

sed -i -e 's/27001/27002/g' -e 's/s1/s2/g' s2/sentinel.conf
sed -i -e 's/27001/27003/g' -e 's/s1/s3/g' s3/sentinel.conf

4、 start-up

For the convenience of viewing the log , We turn on 3 individual ssh Windows start separately redis（ stay /tmp Directory execute the following command ）：

#  The first 1 individual 
redis-sentinel s1/sentinel.conf
#  The first 2 individual 
redis-sentinel s2/sentinel.conf
#  The first 3 individual 
redis-sentinel s3/sentinel.conf

After starting ：

 

5、 test

Try to make master node 7001 Downtime , see sentinel journal ：

see 7003 Log ：

see 7002 Log ：