1000VU, I have some messages missing

Grafana k6
1

less than 20vu, the number of received messages is greater than that of sent messages. 1000vu, the received message is less than the sent message.What’s the reason?

import ws from 'k6/ws';
import { check, sleep } from 'k6';
 
  export let options = {
    stages: [
      { duration: '20m', target: 1000 },
      // { duration: '10m', target: 1000 },
    ],
  };

export default function (tuid,suid,classRoomName) {
  console.log(`VU ${__VU} `);
  
  var classPeople = 5;//Set class capacity 1V4

  var isTeacher = true;
  if (`${__VU}`% classPeople == 1) {
    isTeacher=true;
    tuid=`10032${__VU}`;
    console.log('teacheruid'+tuid);

  }else{
    isTeacher=false;
    suid=`20022${__VU}`;
    console.log('studentuid'+suid);

  }

  var roomId= Math.floor((__VU-1)/classPeople+1);
  classRoomName='test'+roomId;
  
 
  var url;
  if (isTeacher) {//teacher
   url= `wss://msghub.sim.kk.com/connect/token/${classRoomName}/?uid=`+tuid+``;

  }else{// student
   url= `wss://msghub.sim.kk.com/connect/token/${classRoomName}/?uid=`+suid+``;

  }
  console.log(`VU ${__VU}:`+ url);

  const params = {
   // tags: { my_tag: 'my ws session' } 
  };

  var version ;
  var stu_version;
 
  const res = ws.connect(url, params, function (socket) {
    socket.on('open', function open() {
      console.log(`VU ${__VU}: connected`);
      
      if (isTeacher) {
        console.log('tea：'+tuid);
        
        for (var i = 1; i <= classPeople-1; i++) { 
          socket.send(JSON.stringify(message));//
          
        }
        
        socket.send(JSON.stringify(message));
       
        socket.setInterval(function timeout() {
      
          socket.send(JSON.stringify(message}));
          version++;
          socket.send(JSON.stringify(message));
          version++;
        }, 3000); 
      } else {
        
        socket.send(JSON.stringify(mesage));

        socket.send(JSON.stringify(messge));
       
        socket.setInterval(function timeout() {

          socket.send(JSON.stringify(message}));
          stu_version++;
          socket.send(JSON.stringify(message));
          stu_version++;
        }, 3000); 
      }
    });
  
  
    socket.on('close', function () {
      console.log(`VU ${__VU}: disconnected`);
    });

   
    socket.on('message', function (message) {
      console.log(`VU ${__VU} received :` , message);

      const msg = JSON.parse(message);
     
      // {"result":null,"id":1}
      if (msg.id == 1) {
        if (msg.result == null) {
          // console.log('message_id_1');
          version=1;
        } else {
          version = msg.result.version;
          version++;
        }
      }
     
    
      if (msg.id == 4) {
        if (msg.result == null) {
          stu_version=1;
        }else{
          stu_version=msg.result.version;
          stu_version++;
        }
      }
    });
     
  
    socket.setTimeout(function () {
      socket.close();
    }, 30000);
  
  });

  check(res, { 'Connected successfully': (r) => r && r.status === 101 });

}

output:

image
image865×284 7.17 KB

3

Why, some VUs did not start, or some vUs started but did not execute its own default function

4

Hi @bingbing,

Why, some VUs did not start, or some vUs started but did not execute its own default function

It seems some connections are timed out, you should set a lower timeout value and log for getting feedback, it could be useful also to set an error handler as explained in this documentation’s example.

Is the value of iteration_duration expected for you?

5

Thank you for your answer@codebien
set a lower timeout value。I’m getting more messages. But you’ll still get a lot less messages。

Set vu1000, websocket pressure test, CPU only reached 3%, what is the reason?

6

Hi @bingbing,

Is your system returning errors? The response should be explained by understanding the errors returned and why requests have timed out.

It could be useful to me if you could post some metrics’ chart using one of the k6 Output avaialable.

7

1000vus，Set a low timeout period and Error handler，If you can help solve the following three problems, I will be very grateful
1、cpu7.3%

image
image910×336 21.1 KB

image

2、Metrics ws_msgs_received less than ws_msgs_sent

image
image869×304 6.94 KB

3、Some error messages were received

image
image963×468 11.9 KB

Output indicator chart：

image
image965×443 11 KB

2022-02-22_190221 websocket
2022-02-22_190221 websocket965×443 11 KB

8

@codebien Requesting you to please help me with the above query.

9

Hi @bingbing,
is the server or client responsible for closing the WebSocket connection in your application? What is the p(95) value for iteration duration in the 20VUs case? Is it mostly the same?

Have you checked that your server is handling the connections properly and it’s not experiencing any trouble at scale?

  • You could check logs and see if any error is generated from your application
  • The CPU is not the unique value to check: if the application depends on other services/components then the high latency could be generated on that side. You should check the tracing of your system.