How to share data problems with multiple processes of cluster modules in Nodejs _node.js

mentioned earlier

Nodejs added a module cluster to implement multiple processes after v0.6.x, using child_process modules to create and manage processes, and to increase the performance of programs on multi-core CPU machines. This article describes the problem of how to share data with multithreading created using the cluster module.

Inter-process data sharing

Let's start with a simple example of the following code:

var cluster = require (' cluster '); 
var data = 0;//Defines that data is not shared by all processes, each process has its own memory area 
if (cluster.ismaster) {//main process 
 var Numcpus = require (' OS '). CPUs (). length; 
 for (var i = 0; i < Numcpus i++) { 
  var worker = Cluster.fork (); 
 } 
 data++; 
 Console.log (' Data VALUE in mainprocess:%d ', data);
} else {//subprocess, will be invoked Numcpus 
 data++; 
 Console.log (' Data VALUE in childprocess%d:%d ' cluster.worker.id, DATA);
}

The results of the operation are as follows:

Why should variables declared outside of the main process code block and the child Process code block not be global variables? The answer is in the negative. Because each process has its own area in memory, the data++ operation is performed in its own area, which means that the variable data is not shared. So how do you share data between processes? Look at the following code:

var cluster = require (' cluster '); 
var http = require (' http '); 
 
if (cluster.ismaster) { 
 var Numcpus = require (' OS '). CPUs (). length; 
 var data = 0; 
 Start multiple processes. 
 for (var i = 0; i < Numcpus i++) { 
 //Add a process 
 var worker_process = Cluster.fork (); 
 Message Event 
 worker_process.on (' message ', function (msg) { 
  if (msg.cmd && msg.cmd = = ') Listening for child processes Notifyrequest ') { 
  data++; 
  Console.log (' Data VALUE:%d ', data);}} 
 ); 
 } 
else { 
 process.send ({cmd: ' notifyrequest '}); 
}

The results of the operation are as follows:

Therefore, if you need to share data, you need to use message notifications between processes to achieve this goal.

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