Crazy God redis notes 12

Manually configure the host after downtime

 

We put 81 As 80 The host .

Check it again 81 Information about ：

 

Now its host is no longer 6379, It is 6380 了 .

We can see now 79 The service of the port has only one slave .

We can see our 80 Although there are both master and slave , But its permissions are still written from the slave .

our 80 Still can't write .

 

 

We can see us 80 Can get it 79 Written information ,81 The host is 80, however 80 The host is 79, therefore 81 You can get 79 Written information . 

This model is called layer by layer link , Different from the way we copied before .

But in fact, we will not use these two methods .

Now let's 79 The port is closed ：

  So now can we 80 and 81 Choose the eldest of the two port services ？

This is a bit of a plot to usurp the throne . Usually before sentinel mode appears , We all do it manually .

 

At present, both of them are slaves .

 

 

We will manually turn itself into the boss now .

Let's restart now 6379：

 

6379 yes master.

 

But we can see 6380 Still the boss .

If the boss comes back at this time , You can only reconnect .

 

We can let him be a younger brother again .

Now we return to 6379 Host computer , The other is the one master and two slave mode of its slave , To learn the next sentinel mode , This is the point .

Sentinel mode ：

 

 

 

 

Let's test ：

Our current state is one master and two slaves , We need to configure our sentry ：

 

Create a sentinel file ;

 

This is our voting mechanism , Let's Watch 6379.

sentinel monitor The name being monitored host port 1

The following number 1, On behalf of the host is hung up , Vote from the machine to see who becomes the host , The one with the most votes will become the host .

Then let's start our sentry ：

 

We can see the documents that manage our sentry .

 

 

 

After we set the value for him , Then we'll turn it off .

 

my 6380 It's a mainframe .

If master The node is disconnected , At this time, one will be randomly selected from the slave .（ Here is a voting algorithm ） 

Sentinel mode ：

Let's put 6379 Connect it again :

It is no longer a host , Instead, it becomes a slave .

 

We'll find out about us 6379 Service has also become 80 Slave of .

If the host comes back at this time , Can only merge under the new host , As a slave , That's the rule of sentinel mode .

 

 

 

 

Cache penetration and avalanche ：

 

 

 

 

 

 

 

 

 

 

our redis The basic content of is over .