wwindowskill

node-wwindowskill

Enhance node's process.kill to support signals in Windows

Installation

$ npm install wwindowskill

Features

• No code change is needed. Just old process.kill calls.
• Support Both x86 & x64 Windows
• No effect on Non Windows operation systems (Linux, Mac OS X, etc...)
• Support both SIGINT and SIGBREAK (Just the two signals that are available on Windows)

Why wwindowskill?

Sending signal to another process, just by knowing it's PID, is not available at Windows OS. It's a POSIX OSes feature. But, sending signal to other process, for telling it that something is going to happen to you, is a way to give other process some time for graceful shutdown/restart. wwindowskill tries to fix this issue by bringing the ability to send signals, SIGINT and SIGBREAK, to another process by PID.

How it works?

To read a detailed info please visit wwindowskill-library Readme.

Limitations

To send the signal, wwindowskill at first send a same signal to the process that is calling it, to find a thread address. Then the founded address is used to send the real signal. Because of this, the process that is sending the signal will get the same signal too. But wwindowskill register a signal handle during this procedure, so the process will not terminate. But if the process that is sending signal has child process, or is a child process of another process, sending signal will trigger the signal handles in other process in the same process group. And the default behavior of Windows console/application in case of getting a SIGINT or SIGBREAK, is to terminate.

sum up: If you are sending signal in node app that has child process (any kind of it), or is a child process of another process, the result is the termination of all the processes in the same process group, except the sender (well if it's a child process, because the master is terminated, it will terminate too).

PS: Currently there is no solution for this problem. But I'm working on it, to find a solution. Solutions for different scenarios added.

• Parent process only send signal
• Cluster master only send signal

PS-1: A solution for parent processes that wants to send signal (no way for child processes currently), is added. It's setting the warmUp: true option when first calling the wwindowskill in parent, before any child processes creation.

Usage

wwindowskill expose a function. Simply run the exposed function with/without the options. Thats it. It should be called before any usage of process.kill.

By default, wwindowskill will enhance the node's process.kill in a way, that no code changes are needed in your codebase. Enhance means that wwindowskill will replace the node's process.kill with a custom function with the same arguments and functionality. Just some changes to achieve signaling in Windows.

Simplest usage

The returned function from calling the exported function, could be used to send signal, just like the way you call process.kill. It will accept two argument. a PID and a SIGNAL.

/*
    Require and call the function that's exported.
    The returned function can be used to send signal.
*/
var windowsKill = require('wwindowskill')();

/*
    By default, process.kill is enhanced (only in Windows OS),
    so you can either call process.kill, or the returned function.
*/
process.kill(PID, SIGNAL);
windowsKill(PID, SIGNAL);

/*
    Just call the function, and no need to change any code.
    Every process.kill calls in your code, will now enhanced.
    Just need to call wwindowskill, before any call of
    process.kill.
*/
require('wwindowskill')();

process.kill(PID, SIGNAL);

Options

Options and default values are:

const defaultOptions = {
    replaceNodeKill: true,
    warmUp: false
};

replaceNodeKill

This option will tell the wwindowskill that should it enhance/replace the nodes process.kill? By setting true (default value), the nodes process.kill will replaced by a custom function. This custom function will check the signal that is sending using process.kill. If the signal is a member of supported signals, which is SIGINT or SIGBREAK, it will call the modules function that is responsible for sending signal. Otherwise, the signal and pid will be passed to the node's original process.kill.

const options = {
    replaceNodeKill: true, // Should wwindowskill enhance/replace node's process.kill? Default: true
};

require('wwindowskill')(options);

process.kill(PID, SIGNAL);

const options = {
    replaceNodeKill: false // Should windows kill enhance/replace node's process.kill. Default: true
};

var windowsKill = require('wwindowskill')(options);

windowsKill(PID, SIGNAL);

warmUp

By setting warmUp to true, wwindowskill will find and save the ctrl-routine addresses, without any need to send signal. By default, the address will find, when the first signal of that type is sending. Future call will use the founded address.

const options = {
    warmUp: true, // Should wwindowskill warm-up by finding the ctrl-routines addresses? Default: false
};

require('wwindowskill')(options);

process.kill(PID, SIGNAL);

Warm-up, is one way to overcome the limitations. Setting this option, will make the wwindowskill to find needed address, before any signal sending. As stated in limitations section, finding address will cause the processes that have child process, or is a child process, trigger the ctr-routine of all process group members, which means termination of all of them. But warm-up mechanism can be used, to fix the issue in parent process. By setting it to true, before any child process creation, sending signal in future will use the save addresses and no need to find addresses again.

Parent process only send signal

var options = {
    warmUp: false
};

var cp = require('child_process');
var windowsKill = require('wwindowskill')(options);

var cp1 = cp.spawn('node', ['cp.js']);

windowsKill(PID, 'SIGINT');

By running the above code, the cp1 child process will terminate. Because the SIGINT signal is sent for the first time, and the ctrl-routine address in not available. So wwindowskill will try to find it, and trying to find it will trigger the SIGINT handler of cp1 child process, which lead to termination of cp1.

To solve the issue, we can set the warmUp option true. Just remember, the initialization of wwindowskill with warmUp option should be done before any child process creation. Like below:

var options = {
    warmUp: true
};

var cp = require('child_process');
var windowsKill = require('wwindowskill')(options);

var cp1 = cp.spawn('node', ['cp.js']);

windowsKill(PID, 'SIGINT');

Cluster master only send signal

To avoid the termination of child processes (forks), you should use warmUp option in the master creation part.

var cluster = require('cluster');
var os = require('os');

if (cluster.isMaster) {
    /*
        Initialize wwindowskill here. Before and child process creation,
        just in the master process code.
    */
    var windowsKill = require('wwindowskill')({
        "warmUp": true
    });

    for (let i = 0; i < os.cpus().length; i++) {
        cluster.fork();
    }
} else {
    /* Child Process code, that is not using wwindowskill*/
}

Contributing

We love contributions from everyone. Please read Contributing guide.

License

MIT