Redis configuration (III) -- master-slave replication

Redis Master slave copy

What is it? ？

Master slave copy ： After the host data is updated, according to the configuration and Policy , Automatic synchronization to the standby machine master/slaver Mechanism ,Master Write first ,Slave Mainly reading

use ：

• Read / write separation , Performance expansion
• Rapid disaster recovery

Configure temporary slave server ：

step ：

1. Set up three conf file , Port number 、 The file names are different
   
   
2. Start with these profiles redis
   
3. View server status info replication, You can see that each server is the primary server
   
4. Set up a slave server called a server ：slaveof ip port
   Set up 6380 and 6381 by 6379 From the server
   
5. see 6379：
   

Configure permanent master-slave servers

Configure in profile ：

# Master-Slave replication. Use slaveof to make a Redis instance a copy of
# another Redis server. A few things to understand ASAP about Redis replication.
#
# 1) Redis replication is asynchronous, but you can configure a master to
# stop accepting writes if it appears to be not connected with at least
# a given number of slaves.
# 2) Redis slaves are able to perform a partial resynchronization with the
# master if the replication link is lost for a relatively small amount of
# time. You may want to configure the replication backlog size (see the next
# sections of this file) with a sensible value depending on your needs.
# 3) Replication is automatic and does not need user intervention. After a
# network partition slaves automatically try to reconnect to masters
# and resynchronize with them.
#
# slaveof <masterip> <masterport>

From the server, you can only read but not write

One master and two slaves ：

1. A slave server goes down , Then the master server performs a write operation , At this point, reconnect the slave server and set the slave server of the master server ; Does the slave server still have the value written by the master server during this period ？
   answer ： Yes , Whenever programming the slave server of the master server , Have all the data of the master server
2. Whether the slave can write ？
   answer ： Can not be
3. host shutdown What happens after ？
   answer ： The slave machine waits in place and waits for the host machine to work .
   

The principle of replication

It's passed down from generation to generation

1. Set again 6381 The primary server of ：slaveof 127.0.0.1 6380
2. 6379 The state of ： and 6381 No contact
   
3. 6380 The state of ： The Lord is 6379, There's another one 6381
   
4. problem ：
   1. If at this time 6379 It's down. ,6380 Still can not be promoted to the primary server , Need to carry out slaveof no one Set up , Set it to not follow any servers
   2. If 6380 It's down. , Then there is no master-slave relationship

Sentinel mode ：

Configure sentinel mode

Activate the sentry ：

Fault problem in sentinel mode ：

Manual downtime 6379, View the sentinel server log ：

selection 6380 For the new master server


see 6380 Details ：

Back online 6379, From the server

The problem is ： Replication delay