I am trying to start redis from node using the child_process module with the following code:
var childProcess = require('child_process');
childProcess.exec('redis-server --port 6380', function(err, stdout, stderr) {
console.log(err, stdout, stderr);
})
When I run it, the callback is never called. I can see that my redis-server has started on port 6380 using ps auwx | grep redis-server so I don't get why this callback is not called.
Note that when I run redis-server --port 6380 in my terminal, redis starts just fine as well.
I've tried this with memcached instead and it works fine.
What is the reason why this callback is not called?
Many thanks
Because the callback is called only when the process terminates.
If you need to check whether the redis process has finished initializing you can use spawn with event handlers for stdout.
Related
Say that I am running a process from the command line (NOT a nodejs app):
myProcess doSomething --withParam1
I am also running a nodejs app that connects to this process (rpc).
node myApp
myProcess will randomly silently fail to work properly without crashing and myApp will detect it. I need myApp to be able to restart myProcess (kill it and start it again). After I restarted myProcess, myApp will also restart itself using pm2 (I am already handling the pm2 restart part for the nodejs app - my issue is that I cannot use pm2 to restart myProcess since it is not a nodejs app). Also, I cannot change the code of myProcess since it is a 3rd party software.
How can I restart the external process from my nodejs app?
I ended up using process.kill to kill the process and nodejs child process to restart it.
To find the pid of the process before killing it, I used this:
const childProcess = require('child_process');
function printPid() {
childProcess.exec('pidof -s myProcess', function(error, stdout, stderr) {
if (error) {
console.log(error);
} else {
console.log(stdout);
}
});
}
I'm trying to use pm2 to run my node app as a service.
Right now, starting and stopping the app works. However, I want to do a graceful shutdown.
My app already listens for SIGINT, shutdowns the server and then exits the process. However, trying to put pm2 to send the SIGINT, just causes the app to restart, like if pm2 was killing and starting it again.
This is how I create the process:
pm2 start server.js --name ProcessName --silent --kill-timeout 3000
Here's my app's code for listening the SIGINT:
process.on("SIGINT", function () {
//graceful shutdown
server.end().then(() => {
process.exit();
}).catch((err) => {
console.error(err);
});
});
Then to shutdown the app using pm2, I'm running:
pm2 sendSignal SIGINT ProcessName
Which, again, restarts the app.
Reading over pm2 docs, I found that pm2 will also send a shutdown event to the app, so I added:
process.on('message', function(msg) {
if (msg == 'shutdown') {
server.end().then(() => {
process.exit();
}).catch((err) => {
console.error(err);
});
}
});
Which isn't working either.
Any idea how to solve this?
Thanks!
If you haven't solved it yet...
Based on the information you provided, I assume you are running it on Windows.
Your app cannot catch SIGINT sent by PM2 on Windows.
shutdown message works on windows too, but it is sent only by gracefulReload command.
(update)
These are not complete solutions, but might be helpful (hopefully...)
sendSignal command calls process.kill() eventually, and some of these signals might work (haven't tried).
I also found the below method. This can gracefully shutdown a process without restarting only if autorestart option is turned off.
And then your clusters will not reload in case of an accident, so it might not be what you want though...
pm2 lets you send a custom message (reference).
Put the code below in a new file:
var pm2 = require('pm2');
var id = process.argv[2];
pm2.connect(() => {
pm2.sendDataToProcessId({
type: 'shutdown',
data:{some: 'data'},
id: id,
topic: 'some topic'
}, (err, res) => {
console.log('message sent');
pm2.disconnect();
if(err) throw err;
})
});
Modify the part that listens the shutdown message like below:
process.on('message', function(msg){
if(msg == 'shutdown' || msg.type == 'shutdown'){
// code to clean up
}
});
And run the first file with node with id of the cluster you want to shutdown as an argument.
The reason for extra msg.type == 'shutdown' in the condition is that pm2.sendDataToProcessId() requires the argument to be an object with those keys, and does not accept simple shutdown string.
In general pm2 stop is the right way to stop your application. However if you run appliation inside of the Docker you need to use pm2-runtime instead of pm2 which is a part of pm2 npm package and passes system SIGINT to all child processes. See http://pm2.keymetrics.io/docs/usage/docker-pm2-nodejs
Catching the sigint and exiting gracefully should work in your first example.
To actually stop the server, use pm2 stop instead of pm2 sendSignal SIGINT ProcessName.
See http://pm2.keymetrics.io/docs/usage/signals-clean-restart/
I've been browsing around but to no success. I've found some npm packages like nodemon and forever but documentation doesn't explain how to call a restart inside the script properly.
I've found this code snippet on another question but I'm not using Express or other frameworks since the script is using a pulling service not a response one.
This is code I've made so far using internal Node.js dependencies but no luck.
'use strict'
process.on('uncaughtException', (error) => {
console.error('Global uncaughtException error caught')
console.error(error.message)
console.log('Killing server with restart...')
process.exit(0)
})
process.on('exit', () => {
console.log('on exit detected')
const exec = require('child_process').exec
var command = 'node app.js'
exec(command, (error, stdout, stderr) => {
console.log(`error: ${error.message}`)
console.log(`stdout: ${stdout}`)
console.log(`stderr: ${stderr}`)
})
})
setTimeout(() => {
errorTriggerTimeBomb() // Dummy error for testing triggering uncaughtException
}, 3000)
Just to note I'm running the server on Termux, a Linux terminal app for android. I know it's better to run from desktop but I'm always at a WiFi or mobile data area and that I don't like leaving my PC on overnight.
A typical restart using something like nodemon or forever would be triggered by calling process.exit() in your script.
This would exit the current script and then the monitoring agent would see that it exited and would restart it for you. It's the same principal as if it crashed on its own, but if you're trying to orchestrate it shutting down, you just exit the process and then the monitoring agent will restart it.
I have a home automation server that is being monitored using forever. If it crashes forever will automatically restart it. I also have it set so that at 4am every morning, it will call process.exit() and then forever will automatically restart it. I do this to prevent any memory leak accumulation over a long period of time and 30 seconds of down time in the middle of the night for my application is no big deal.
I have a very simple node script that waits for an event and then runs an ssh command:
function buildSite(){
exec('/usr/bin/ssh user#server \' cd SiteDir; ./build.sh \' ', function(error, stdout, stderr) {
console.log(stdout)
}); }
If the app is running with nodemon, this works. If I start the app with PM2, I get an event that tells me the command was received, but the site wasn't rebuilt as expected.
Am I missing something and need to accommodate for PM2?
I'm using mocha with Nodejs to test my restApi.
When I run mocha, I tell my test to create a child_process and run the API so I can make requests to it.
The problem is whenever the test exits (finishing or crashing), it seems that the API keeps running on background. I've seen some answers here that instructs to manually kill the child process whenever the main process exits. So I did it like this:
export function startProcess(done) {
const child = spawn('babel-node', ["app.js"]);
child.stdout.on("data", function(data) {
data = data.toString();
// console.log(data.toString());
if(data.indexOf("Server online") > -1) done();
});
child.stderr.on('data', function(err) {
console.log("ERROR: ", err.toString());
});
child.on('exit', function(code) {
console.log("PROPERLY EXITING");
console.log("Child process exited with code", code);
});
process.on('exit', function(code) {
console.log("Killing child process");
child.kill();
console.log("Main process exited with code", code);
});
}
When the main process exits it does log "Killing child process", meaning that child.kill() was indeed called. But if I try to run my test again, when the spawn command gets called, the API throws an error
Error: listen EADDRINUSE :::3300
, meaning that the API is still running and that port address is taken.
So I have to run sudo pkill node to really kill all node process and then npm test works again.
Am I missing something? Is this really the way to achieve what I'm expecting?
I thought about using child_process.exec to run sudo pkill node on my process.on('exit') listener, but that doesnt seem like a smart thing to do.
This is happening both in Mac and Ubuntu.
Any suggestions?
Thanks
"exit" is an event that gets triggered when node finishes it's event loop internally, it's not triggered when you terminate the process externally.
What you're looking for is executing something on a SIGINT.
Have a look at http://nodejs.org/api/process.html#process_signal_events