[redis foundation] understand redis master-slave architecture, sentinel mode and cluster together (Demo detailed explanation)

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One 、 Master slave architecture

In this issue, I will study with you Redis Master slave architecture 、 Sentinel mode 、 Basic concepts related to clusters ！

Master slave synchronization ：Master After the node receives the write request and processes it , Need to inform Slave The node data has changed , The behavior of keeping the data of master-slave nodes consistent is called master-slave synchronization

Read / write separation ： stay redis In the master-slave architecture ,Master The node is responsible for processing write requests ,Slave The node only processes read requests . Fewer write requests , Scenarios with many read requests

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One master, many followers ： Structure optimization

If there are many slave nodes , To ease the master-slave replication storm ( Multiple slave nodes copy the master node at the same time, which leads to excessive pressure on the master node ), You can do the following Architecture , Let part of the slave node and slave node ( Synchronize with the master node ) Synchronous data

If the Lord master Hang up ？

If an instance master Hang up , We need to manually switch one from the server to the main server , It will also make the service unavailable for a period of time .

In order to solve the problem that the master-slave mode cannot be highly available , He invented the sentinel mode

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Two 、 Sentinel mode

What is a sentry

1、sentinel Sentinels are special redis service , No read-write service , It's mainly used to monitor redis Instance node .

2、 Sentinel mode is a special mode ,Redis The order of the sentry , Sentinels are an independent process , As a process , It will run on its own . The sentry sent orders , wait for Redis Server response , So as to monitor the operation of multiple Redis example .

The main role of the sentry

1、 By sending commands , Give Way Redis The server returns to monitor its running state , Including the master and slave servers .

2、 When the Sentinels detect master Downtime , Will automatically slave Switch to master, Then the other slave servers are informed through publish subscribe mode , Modify the configuration file , Let them switch hosts .

When redis The master node of the , The Sentinels will be aware of , And the new redis The master node notifies client End ( Inside this redis Of client The end generally implements the subscription function , subscribe sentinel Published node change message )

Sentinel mode , Must be based on redis Done in master-slave replication mode

summary ： Sentinel mode , It is based on the original master-slave architecture , Another cluster , The sentry cluster , This cluster will monitor redis The status of the master and slave nodes of the cluster , If you find that the primary node is hung , One of the slave nodes will be selected as the master node again , So as to achieve high availability .

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3、 ... and 、 Cluster pattern

Redis Cluster interpretation

Redis Cluster is a distributed server group composed of multiple master-slave nodes , It has replication 、 High availability and fragmentation features .

Redis Cluster architecture

Redis3.0 before ： Configuration instructions

1、 stay redis3.0 In previous versions, clusters were implemented with the help of sentinels sentinel Tools to monitor master The state of the node

2、 If master Node exception , Then we will switch from the master to the slave , Take a certain one slave As master, The sentry configuration is a little complicated , And performance and high availability and other aspects of the general performance

3、 Especially in the moment of master-slave switching, there is an access transient , And the sentinel mode only has one master node to provide external services , Can't support very high concurrency , And the memory of a single primary node should not be set too large , Otherwise, the persistent file will be too large , Affect the efficiency of data recovery or master-slave synchronization

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Redis colony ： Unwanted sentinel sentry

1、Redis Clusters do not need sentinel sentry , It can also complete the function of node removal and fail over .

2、 You need to set each node to cluster mode , There is no central node in this cluster mode , Scalable horizontally , According to official documents, it can be linearly extended to tens of thousands of nodes ( The official recommendation is no more than 1000 Nodes ).

3、redis Cluster performance and high availability are better than the previous version of sentinel mode , And the cluster configuration is very simple

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Basis of this period Redis Master slave architecture 、 Sentinel mode 、 Cluster graphic explanation , Later, it will be updated one after another , See you next time ……

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2021 year 11 month 26 Japan 22:42:21 May we go in our love ！