I am running a nodejs HTTP server packaged as an exe binary with the pkg npm module. I need to run it as a windows service. It works perfectly when started normally. But here is what happens if I run it as a windows service:
I start the service.
Windows attempts to start the service.
During this time, the HTTP server is accessible, and works perfectly
Windows services times out with the error after 30 seconds: "The service did not respond to the start or control request in a timely fashion."
It seems to me that I somehow have to inform windows that my service has started, let me just stay open.
How can I do that?
A regular application can't work as Windows service. As the reference states, the implementation should satisfy certain requirements,
the interface requirements of the service control manager (SCM) that a service program must include:
Service Entry Point
Service ServiceMain Function
Service Control Handler Function
There is os-service package that allows to install a service that starts Node.js script. Current script is considered entry point by default:
const osService = require('os-service');
const [action] = process.argv.slice(2);
function errorHandler(err) {
if (!err) return;
console.error(err);
process.exit(1);
}
if (action === '--install') {
osService.add('Foo', errorHandler);
} else if (action === '--uninstall') {
osService.remove('Foo', errorHandler);
} else {
// report service as running
osService.run('Foo', () => {
osService.stop();
});
// app entry point
}
Not sure if this is a service fabric issue, or issue with node.js.
Basically this is my problem. I deploy the node.js application, it works fine. I redeploy the node application it fails to work, with the server returning EADDRINUSE. When I run netstat -an the port isn't in use. It's as if node is still running somewhere, some how, but not appearing in tasklist etc..
Anyone got any ideas?
Not entirely sure, but I believe this is because the server I was using (express.js), or rather node, was not shutting down and closing existing connections causing windows to think the ports are still in use. At least, that's how it seems.
I can not find it "officially" documented, but from this (quoted below) it reads SF sends SIGINT to the application to attempt to end it before killing it.
The following code appears to fix my issue:
var app = express();
var server = app.listen(17500);
if (process.platform === "win32") {
var rl = require("readline").createInterface({
input: process.stdin,
output: process.stdout
});
rl.on("SIGINT", function () {
process.emit("SIGINT");
}
}
process.on("SIGINT", function() {
server.close(function () {
process.exit(0);
});
});
For Linux nodes, I suppose you'd want to listen for "SIGTERM" as well.
I would like to know if there's any sort of remediation for this though, in the previously mentioned scenario the VMSS was completely unusable -- I could not deploy, nor run, a node web server. How does one restart the cluster without destroying it and recreating it? I now realise you can't just restart VMSS instances willy-nilly because service fabric completely breaks if you do that, apparently irrevocably
Rajeet Nair [RajeetN#MSFT]
Service Fabric also sends a Ctrl-C to service processes and waits for service to terminate. If the service doesn't terminate for 3 minutes, the process is killed.
I am running a simple script in azure mobile services scheduler:
function warmup() {
warmUpSite("http://safenoteit.ca/");
}
function warmUpSite(url) {
console.info("warming up: " + url);
var req = require('request');
req.get({ url: url }, function(error, response, body) {
if (!error) {
console.info("hot hot hot! " + url);
} else {
console.error('error warming up ' + url + ': ' + error);
}
});
}
This runs as expected when I manually run it (Run once button). However, despite scheduling it to run every 15 minutes, I don't see any console log messages coming from the script. Additionally, the portal tells me that the scheduler is enabled and running:
Anyone else see this issue? The mobile service is running on basic tier and I have very little load on it. I don't see what could cause this issue, which makes the whole scheduler service useless.
UPDATE: Tried the same scheduled script on another mobile service, and everything works! Something's messed up with the mobile service itself. Talking to Microsoft support to resolve this.
It was an issue only Microsoft can fix. They had to redeploy the mobile service.
This code is based on wintersmith static site generator
In my code I'm starting the preview server like this:
env.preview(function(error, server) {
if (error) throw error;
console.log('Server running!');
setTimeout(function(){
console.log("going to shut it down")
server.stop();
}, 3000)
});
This is taken from the example. I would expect the preview server to stop after 3 seconds, but instead I get an error, that server is undefined.
I looked a bit closer at it and indeed: server is undefined. Anything I'm doing wrong? How am I able to stop the preview server?
This looks like a bug, create an issue on github and i'll have a look at it when i get some time.
From my experience, a php server would throw an exception to the log or to the server end, but node.js just simply crashes. Surrounding my code with a try-catch doesn't work either since everything is done asynchronously. I would like to know what does everyone else do in their production servers.
PM2
First of all, I would highly recommend installing PM2 for Node.js. PM2 is really great at handling crash and monitoring Node apps as well as load balancing. PM2 immediately starts the Node app whenever it crashes, stops for any reason or even when server restarts. So, if someday even after managing our code, app crashes, PM2 can restart it immediately. For more info, Installing and Running PM2
Other answers are really insane as you can read at Node's own documents at http://nodejs.org/docs/latest/api/process.html#process_event_uncaughtexception
If someone is using other stated answers read Node Docs:
Note that uncaughtException is a very crude mechanism for exception handling and may be removed in the future
Now coming back to our solution to preventing the app itself from crashing.
So after going through I finally came up with what Node document itself suggests:
Don't use uncaughtException, use domains with cluster instead. If you do use uncaughtException, restart your application after every unhandled exception!
DOMAIN with Cluster
What we actually do is send an error response to the request that triggered the error, while letting the others finish in their normal time, and stop listening for new requests in that worker.
In this way, domain usage goes hand-in-hand with the cluster module, since the master process can fork a new worker when a worker encounters an error. See the code below to understand what I mean
By using Domain, and the resilience of separating our program into multiple worker processes using Cluster, we can react more appropriately, and handle errors with much greater safety.
var cluster = require('cluster');
var PORT = +process.env.PORT || 1337;
if(cluster.isMaster)
{
cluster.fork();
cluster.fork();
cluster.on('disconnect', function(worker)
{
console.error('disconnect!');
cluster.fork();
});
}
else
{
var domain = require('domain');
var server = require('http').createServer(function(req, res)
{
var d = domain.create();
d.on('error', function(er)
{
//something unexpected occurred
console.error('error', er.stack);
try
{
//make sure we close down within 30 seconds
var killtimer = setTimeout(function()
{
process.exit(1);
}, 30000);
// But don't keep the process open just for that!
killtimer.unref();
//stop taking new requests.
server.close();
//Let the master know we're dead. This will trigger a
//'disconnect' in the cluster master, and then it will fork
//a new worker.
cluster.worker.disconnect();
//send an error to the request that triggered the problem
res.statusCode = 500;
res.setHeader('content-type', 'text/plain');
res.end('Oops, there was a problem!\n');
}
catch (er2)
{
//oh well, not much we can do at this point.
console.error('Error sending 500!', er2.stack);
}
});
//Because req and res were created before this domain existed,
//we need to explicitly add them.
d.add(req);
d.add(res);
//Now run the handler function in the domain.
d.run(function()
{
//You'd put your fancy application logic here.
handleRequest(req, res);
});
});
server.listen(PORT);
}
Though Domain is pending deprecation and will be removed as the new replacement comes as stated in Node's Documentation
This module is pending deprecation. Once a replacement API has been finalized, this module will be fully deprecated. Users who absolutely must have the functionality that domains provide may rely on it for the time being but should expect to have to migrate to a different solution in the future.
But until the new replacement is not introduced, Domain with Cluster is the only good solution what Node Documentation suggests.
For in-depth understanding Domain and Cluster read
https://nodejs.org/api/domain.html#domain_domain (Stability: 0 - Deprecated)
https://nodejs.org/api/cluster.html
Thanks to #Stanley Luo for sharing us this wonderful in-depth explanation on Cluster and Domains
Cluster & Domains
I put this code right under my require statements and global declarations:
process.on('uncaughtException', function (err) {
console.error(err);
console.log("Node NOT Exiting...");
});
works for me. the only thing i don't like about it is I don't get as much info as I would if I just let the thing crash.
As mentioned here you'll find error.stack provides a more complete error message such as the line number that caused the error:
process.on('uncaughtException', function (error) {
console.log(error.stack);
});
Try supervisor
npm install supervisor
supervisor app.js
Or you can install forever instead.
All this will do is recover your server when it crashes by restarting it.
forever can be used within the code to gracefully recover any processes that crash.
The forever docs have solid information on exit/error handling programmatically.
Using try-catch may solve the uncaught errors, but in some complex situations, it won't do the job right such as catching async function. Remember that in Node, any async function calls can contain a potential app crashing operation.
Using uncaughtException is a workaround but it is recognized as inefficient and is likely to be removed in the future versions of Node, so don't count on it.
Ideal solution is to use domain: http://nodejs.org/api/domain.html
To make sure your app is up and running even your server crashed, use the following steps:
use node cluster to fork multiple process per core. So if one process died, another process will be auto boot up. Check out: http://nodejs.org/api/cluster.html
use domain to catch async operation instead of using try-catch or uncaught. I'm not saying that try-catch or uncaught is bad thought!
use forever/supervisor to monitor your services
add daemon to run your node app: http://upstart.ubuntu.com
hope this helps!
Give a try to pm2 node module it is far consistent and has great documentation. Production process manager for Node.js apps with a built-in load balancer. please avoid uncaughtException for this problem.
https://github.com/Unitech/pm2
Works great on restify:
server.on('uncaughtException', function (req, res, route, err) {
log.info('******* Begin Error *******\n%s\n*******\n%s\n******* End Error *******', route, err.stack);
if (!res.headersSent) {
return res.send(500, {ok: false});
}
res.write('\n');
res.end();
});
By default, Node.js handles such exceptions by printing the stack trace to stderr and exiting with code 1, overriding any previously set process.exitCode.
know more
process.on('uncaughtException', (err, origin) => {
console.log(err);
});
UncaughtException is "a very crude mechanism" (so true) and domains are deprecated now. However, we still need some mechanism to catch errors around (logical) domains. The library:
https://github.com/vacuumlabs/yacol
can help you do this. With a little of extra writing you can have nice domain semantics all around your code!