Nodejs solves the problem of how to share data among multiple processes in the cluster module, nodejscluster

Nodejs solves the problem of how to share data among multiple processes in the cluster module, nodejscluster

Aforementioned

Nodejs added a cluster module after v0.6.x to implement multi-process. It uses the child_process module to create and manage processes and increase program performance on multi-core CPU machines. This article describes how to share data using the multi-thread created by the cluster module.

Data sharing between processes

The Code is as follows:

Var cluster = require ('cluster'); var data = 0; // data defined here is not shared by all processes. Each process has its own memory region 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 {// sub-process, called numCPUs data ++; console. log ('data VALUE in ChildProcess % d: % d' cluster. worker. id, data );}

The running result is as follows:

Why shouldn't the variables declared outside the main process code block and sub-process code block be global variables? The answer is no. Because each process has its own region in the memory, the data ++ operation is performed in its own region, that is, the variable data is not shared. So how can we share data between processes? Let's 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 (); // listen to the message event worker_process.on ('message', function (msg) {if (msg. cmd & msg. cmd = 'policyrequest') {data ++; console. log ('data VALUE: % d', DATA) ;}} else {process. send ({cmd: 'policyrequest '});}

The running result is as follows:

Therefore, to share data, you need to use message notifications between processes.

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