IO multiplexing of 09 redis

Catalog

One Redis Single thread or multi thread ？

Two Why single threaded Redis A high performance ？

3、 ... and What is? IO Multiplexing technology ？

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One Redis Single thread or multi thread ？

This problem can be divided into two ：

Redis A single thread , Because Redis Use the file event dispatcher to handle the event queue , And the file event dispatcher is single threaded , therefore Redis It's called a single threaded model .

Redis Is a multithreaded , Because persistence 、 Delete asynchronously 、 Cluster data synchronization and other operations are performed by threads other than data reading and writing threads , therefore Redis It can also be called multithreading model .

The reason why we all say it is single thread , Because it's single threaded Redis A high performance .

Two Why single threaded Redis A high performance ？

1 Redis All the data is stored in memory , Memory operation is fast .

2 Redis Use  IO Multiplexing technology to deal with concurrent events .

This memory is easy to understand , Not much to say , Let's take a closer look at IO Multiplexing technology .

3、 ... and What is? IO Multiplexing technology ？

Pictured here Redis Overall event processing flow chart of client and server ：

The flow chart is mainly composed of the following parts ：

• multiple Socket.
• IO Multiplexing program .
• Event queue .
• File event dispatcher .
• Multi type event handler .

among IO Multiplexing program , Monitor multiple Socket.

With a Socket Examples of various event types .

1 Establish connection event

The client establishes a connection to the server ,IO After multiplexing listens to the request event for establishing a connection , Write the request event to the queue , The file event dispatcher gets the request event from the queue , Give it to the connection response processor for processing .

Connect the response processor with the client to create a Socket.

2 Write request event

The client sends one set key value Request ,IO After multiplexing listens to the write event , Write events to the queue , The file event dispatcher gets the request event from the queue , To the command request processor .

The command requests the processor to implement... In memory  set key value The operation of .

3 Return result event

The client is ready to receive the results ,IO After multiplexer listens to the return result event , Write events to the queue , The file event dispatcher gets the request event from the queue , Give it to the command reply processor for processing .

The command reply processor returns the result .