child process fork call mutiple time in nodejs

Question

im bit confuse why connection trigger multiple time. let first start with my code

main.js

  let Tokens = {};
  app.getOauthToken = async function (host, port, oauthcall = false) {
    if (host !== undefined && port !== undefined) {
       const key = host + ":" + port;
       if (Tokens[key] !== undefined) {
       if(oauthcall){
            console.log("already auth token present (mainjs)")
            await Tokens[key].getAccessToken(false);
            child.send( Tokens[key] )
      }
         return Tokens[key];
    } else {
      Tokens[key] = new Token(host, port);
     if (oauthcall) {
        await  Tokens[key].getAccessToken(false);
        console.log( " auth token in mainjs ------->", Tokens[key].token)
         child.send( Tokens[key] )       
      } 
      return Tokens[key];  
    }
  }
 }
 child.on('message', (m) => {
    console.log(" mess from child ")
    if (m && m.auth) { 
       app.getOauthToken(m.host, m.port, m.oauthcall);
    }
 });

in child.js

    process.send({ "auth": true, "host": url.host, "port": url.port, "oauthcall": true });
   process.on('message', (m) => {
         console.log("msg from parent ------------>", m )
    });

output in 1st attempt (fresh start of main.js)

     mess from child 

     auth token in mainjs -------> { "token" :dsadaq21}  
     msg from parent ------------> { "token" :dsadaq21} 

output in 2nd attempt ( got message in child.js 2 time on process.on "message" )

     mess from child 

     already auth token present (mainjs)
     msg from parent ------------> { "token" :dsadaq21} 

     already auth token present (mainjs)
     msg from parent ------------> { "token" :dsadaq21} 

output in 3rd attempt ( got message in child.js 3 time on process.on "message" )

     mess from child 

     already auth token present (mainjs)
     msg from parent ------------> { "token" :dsadaq21} 

     already auth token present (mainjs)
     msg from parent ------------> { "token" :dsadaq21} 

     already auth token present (mainjs)
     msg from parent ------------> { "token" :dsadaq21} 

can any one tell me is this expected behaviour or im doing something wrong or its bug in nodejs note :- i haven't used any "close" method is this issue due to not using close

Answer 1

You do not show it, but you are loading this each time you send a message:

   process.send({ "auth": true, "host": url.host, "port": url.port, "oauthcall": true });
   process.on('message', (m) => {
         console.log("msg from parent ------------>", m )
    });

However you trigger that process.send also adds another process.on event listener.

If you need to put that process.on in a different scope from the process.send , so that process.on is called only once, and process.send can be called without also executing process.on .

Does that make it clear?

For example:

function startTestLoop() {
 // Set up listener - this must only ever be executed _once_
 // `process.on()` adds _another_ listener callback every time it is run.
 process.on('message', (m) => {
   // This code is the callback. It runs every time the event is fired.
   console.log("msg from parent ------------>", m )
 });

 // Send message every 10 seconds - do this till the cows come home
 const handle = setInterval(() =>  
   process.send({ "auth": true, "host": url.host, "port": url.port, "oauthcall": true }), 
   10 * 1000
  )
}