Manage communication between parent and child processes through IPC asynchronously in NodeJS.
When trying to use child process' functions from the parent process, you need to set up a bunch of listeners on both sides, and if you need to get a response to a specific function call asynchronously forget about it. Listening for messages does not allow to identify which response corresponds to which request(call to a child's function).
This packages solves this problem, allows you to easily call a function on a child process spawned with child_process.spawn(), and have a callback for it.
(on parent process)
let child = spawn("node", ["./child.js"], {stdio:["pipe", "pipe", "pipe", "ipc"]});
child.send("asyncRequest1", "doSomething");
child.send("asyncRequest2", "doSomethingDifferent");
child.on("message", function(reponse){
//this "response" is for asyncRequest1 or asyncRequest2???
console.log(reponse);
});1.- Install it in your project:
npm install ipc-messages-manager -S
2.- Require it:
-
on parent process
var ipcManager_parent = require("ipc-messages-manager").parent; -
on child process
var ipcManager_child = require("ipc-messages-manager").child;
3.- Spawn the child process (on parent process)
var child = require("child_process").spawn("node", ["./child-process.js"], {stdio:["pipe", "pipe", "pipe", "ipc"]});4.- Send message from the parent to child:
ipcManager_parent.send(child, "actionToPerform", {param1:"foo", param2:"bar"}, function(result){
console.log("response to this message was " + result);
});5.- Listen for this message on the child, and provide an answer to it:
ipcManager_child.actions.on("actionToPerform", function(args, callback){
var result = doProcess(args.param1, args.param2);
callback(result);
});or, register a function to be called for each action, all at once:
ipcManager_child.setActions({
"actionToPerform": function(args, callback){
var result = doProcess(args.param1, args.param2);
callback(result);
},
"secondActionToPerform": function(args, callback){
doAsyncProcess(args.param1, function(result){
callback(result);
});
}
});Type: child_process
The child process to whom it will send the message, it should be a process spawned with child_process.spawn() method and with an IPC channel already setup
Type: String
A string to identify the action that needs to be performed on the child instance and answer back to the parent. For example, let's say the child has a addTwoNumbers() function and the parent wants to call it, then it is suggested to set action to be addTwoNumbers to make logical sense, but it's not required.
Type: Object
An object containing the arguments needed to perform "action". These arguments can later be retrieved on the child's listener function. In the example above for action addTwoNumbers, this args object could be something like {number1: 5, number2: 10}.
Type: Function
Function to be called when the child responds back with an answer to this action(message)
The response object will be what the child sent back.
Type: Object
An object containing each action as keys and the value is the function that's going to be executed when that action is requested.
Each function takes 2 parameters, the first one is the args object which contains all arguments (or parameters) for the action requested, and the second one is the callback that needs to be called to return the response back to the parent.
Example:
var actions = {
addTwoNumbers: function(args, callback){
var sum = addTwoNumbers(args.number1, args.number2);
callback(sum);
},
anotherAction: function(argsm callback){
callback("anotherAction performed");
},
...
}Alternatively you can listen (and respond) for specific actions with the ipcManager_child.actions EventEmitter by listening with the on method in the following way:
ipcManager_child.actions.on("addTwoNumbers", function(args, callback){
var sum = addTwoNumbers(args.number1, args.number2);
callback(sum);
});Feel free to open Issues to ask questions about using this package, PRs are very welcome and encouraged.
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MIT © Daniel Nieto