Basic Tutorials of Redis -Publish and Subscribe

Posted 2020-08-08 Catcher Wong

Basic Tutorials of Redis(7) -Publish and Subscribe

　　This post is mainly about the publishment and subscription in Redis.I think you may subscribe some offiial

accounts on wechat,and when the authors published something new to their accounts,you will get them in

your wechat.The instance can make you understand this pattern easily.You will find there only 6 commands

for publishment and subscription.

 　　This post introduces the basic usages as well.I will show you how to publish a message to a channel.publish

is the command to publish sometings.I publish a channel named news-nba with the message nba.And the client

return me a integer 0.What is the meaning of the return value?It means that there is nobody subscribe this channel.

publish news-nba nba

 　　I open a new client for subscriber.In this client,I subscribe the above channel news-nba.It will return something

about this channel.

subscribe news-nba

 　　OK,let\'s publish a new message to the news-nba to see the changes in the both clients.After publishing lakers to

the news-nba channel,this client returns 1.It means that the channel has a subscriber.

publish news-nba lakers

 　　Let\'s turn to the subscriber\'s client.You will find the message lakers was already in the client.So amazing it is.

　　

　　Opening the second client to subscribe this channel,and you will find something similar with the above example.

　　

 　　publish a new message to the news-nba,it returns 2 meaning ...(you understand it)

　　

　　the both subscribers\' client are as follows:

　　

　　

 　　All right,let\'s see the other commands of this feature in Redis.Seeing the sql first:

 select * from channels where channelname like \'news%\' To execute this sql,you will get all of the channel whoes 

name start with news.Redis can also do that to help us subscibe many channels by matching their name vaguely.

For example I want to subscribe all the channels of news.I will use psubscribe to do this job.

psubscribe news-*

　　Let\'s publish some message to the others channel started with news- to find out the changes.

publish news-tech tech

 　　The subscriber\'s client will receive the message from the channel news-tech.

 　　Again!!Publishing a message to a new channel.

 　　As you can see,the client receives this message as well.

　　The client of Redis can not show you the unsubscription.So turning to the StackExchange.Redis.The

following code demonstrates the usage in C#.

 1             //publisher
 2             var sub = redis.GetSubscriber();
 3             //subscriber
 4             var sub2 = redis.GetSubscriber();
 5             
 6             sub.Publish("news-nba", "nba");
 7             sub.Publish("news-tech", "tech");
 8            
 9             //sub
10             sub2.Subscribe("news-nba", (channel, value) =>
11             {
12                 Console.WriteLine(string.Format("{0} has been published to {1}!",value,channel));
13             });
14             sub2.Subscribe("news-tech", (channel, value) =>
15             {
16                 Console.WriteLine(string.Format("{0} has been published to {1}!", value, channel));
17             });
18 
19             sub.Publish("news-nba", "Lakers");
20             sub.Publish("news-nba", "Kobe");
21 
22             sub.Publish("news-tech", "lumia");
23 
24             System.Threading.Thread.Sleep(2000);
25             Console.WriteLine("unscribe the news-nba");
26             sub2.Unsubscribe("news-nba");//unsub
27 
28             sub.Publish("news-tech", "surface pro3");
29 
30             System.Threading.Thread.Sleep(2000);
31             sub.Publish("news-nba", "james");
32 
33             System.Threading.Thread.Sleep(2000);
34             Console.WriteLine("unscribe all channels");
35             sub2.UnsubscribeAll();
36             
37             sub.Publish("news-nba", "paul");
38             sub.Publish("news-tech", "surface pro4");

　　Debuging the code ,you will see the result as follow. 

　　

　　The next post of this series is the basic opreation of transaction in Redis.Thanks for your reading.