Is there any alternative to PHP error_reporting(0) in nodejs? I want to prevent app from closing after an error, I tried the try and catch method, but it doesn't work.
So, how can I prevent node.js server from closing after an error ?
Edit:
There is an event for uncaught errors:
process.on('uncaughtException', function (err) {
console.log('Caught exception: ' + err);
});
See duplicate: Make node.js not exit on error
You could also use pm2 to run your script, pm2 will automatically restart your script on crash.
You need to catch the error.
For example
try {
error();
} catch(err) {
// do nothing
}
There is no other way as far as i know. So you could fix or catch these errors only.
After i review source code of node, I found there is a beautiful method to implement "ctrl+c" existing.
Create file block.js, content is:
const readline = require('readline')
const rl = readline.createInterface({
input: process.stdin,
output: process.stdout
})
const block = (data) => {
process.on('uncaughtException', function (err) {
console.log('Caught exception: ' + err)
})
rl.on('SIGINT', () => {
console.log(data)
rl.pause()
})
}
module.exports = {
block
}
Then require this js file in whatever main js file, and run this:
const { block } = require('./block.js')
block('Your exiting message!')
// your other js code after here
// ...
The block.js file would catch err and "ctrl+c" SIGINT exit.
Related
I am new to NodeJS. The following code snippet from my script is not executing nor it is logging any errors.
console.log('Process attachment');
const simpleParser = require('mailparser').simpleParser;
console.log('Process attachment');
simpleParser(data.Body, (err, mail) => {
if (err) {
console.log('attachment error');
console.log(err)
callback(null, null);
} else {
console.log('attachment success');
console.log(mail)
console.log(mail.attachments[0])
console.log(mail.attachments[0].content)
console.log(mail.attachments[0].content.toString('ascii'))
callback(null, null);
}
})
console.log('Exit');
process.exit();
Process attachment and Exit are being logged in the console but for some reason the code never goes in either the if or the else. So it looks like the simpleParser function is not being executed for some reason. data.Body contains a full email body. Is there anything obvious i am missing ? Thanks.
Why don't you use promises instead ?
This will work
simpleParser(data.Body).then(mail=>{
console.log('attachment success');
console.log(mail)
console.log(mail.attachments[0])
console.log(mail.attachments[0].content)
console.log(mail.attachments[0].content.toString('ascii'))
}).then(()=>{
console.log('Exit');
process.exit();
}).catch(err=>{
console.log('attachment error');
console.log(err);
})
And if you want to make it look simpler, cleaner use Async/Await like this
const parseMail = async ()=>{
try {
let mail = await simpleParser(data.Body);
console.log('attachment success');
console.log(mail)
console.log(mail.attachments[0])
console.log(mail.attachments[0].content)
console.log(mail.attachments[0].content.toString('ascii'))
}
catch(err) {
console.log('attachment error');
console.log(err);
}
console.log('Exit');
process.exit();
}
You are terminating the script prematurely.
simpleParser is being executed asynchronously. Therefore this bit console.log('Exit'); process.exit(); is being called before your simpleParser has finished.
We experienced this exact same behavior. The above responders are correct in that the console.log commands are not logging anything within the mailparser function because it is running asynchronously and the calling function is exiting without waiting on the mailparser to do its thing.
The simple solution for us was to just call the mailparser with await so the calling function waits on mailparser to complete before it continues.
So, instead of:
simpleParser(data.Body, (err, mail) => {console.log('message');});
Try this:
let mail = await simpleParser(data.Body);
if (mail != null) {console.log('message');};
For what it's worth, I think the asynchronous simpleParser function without the await should still be running through its internal code. It's just the logging messages won't be recorded as the calling function may have exited at the time.
the answer to this question: How to get node to exit when mongo connect fails contains async/wait code for a connection
however, my code (running on node v11.5.0 and mongodb v3.1.13) is failing to catch:
(async function() {
let db;
try {
db = await MongoClient.connect(uri, { useNewUrlParser: true });
console.log("RETURN", db);
} catch (err) {
console.log('EXITING');
process.exit(1);
}
}());
to prove the point I intentionally give a uri without credentials:
mongodb://undefined#cluster0-shard-00-00-z4j9e.azure.mongodb.net:27017,cluster0-shard-00-01-z4j9e.azure.mongodb.net:27017,cluster0-shard-00-02-z4j9e.azure.mongodb.net:27017/test?ssl=true&replicaSet=Cluster0-shard-0&authSource=admin&retryWrites=true
and what I get is output like this:
/Users/ekkis/dev/mongo/node_modules/mongodb/lib/topologies/replset.js:346
throw err;
^
MongoError: password must be a string
at passwordDigest (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/auth/scram.js:63:43)
at ScramSHA1.ScramSHA.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/auth/scram.js:175:25)
at authenticate (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:232:17)
at authenticateLiveConnections (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:819:7)
at /Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:864:5
at waitForLogout (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:855:34)
at Pool.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/connection/pool.js:862:3)
at Server.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/topologies/server.js:931:20)
at auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/topologies/replset.js:1474:19)
at ReplSet.auth (/Users/ekkis/dev/mongo/node_modules/mongodb-core/lib/topologies/replset.js:1492:5)
so if the error had been caught, the console should have displayed the word 'EXITING', but does not. additionally, I contend an exception was thrown because otherwise the returned value would have been printed, which it was not
how can this be? what do I need to do to get it to work?
* Appendix I *
In fact, the promises version of this exhibits the same odd behaviour, it doesn't catch:
MongoClient
.connect(uri, { useNewUrlParser: true })
.then(dbc => {
console.log('SUCCESS');
})
.catch(err => {
console.log('EXITING');
process.exit(1);
});
and yes, I tested the callback version, which also suffers the same malady. Incidentally, passing an empty string for the uri works well. I don't get it
* Appendix II *
In fact, the problem seems to be particular to the credentials passed i.e. if I pass:
mongodb://x:y#cluster0-shard-[...]
I catch a "MongoError: authentication fail" as expected. passing:
mongodb://#cluster0-shard-[...]
interestingly returns a connection but credentials missing a ":" fail in this odd way, so:
mongodb://ekkis#cluster0-shard-[...]
fails to catch
Looks to me like it's a bug with however MongoClient is setting up its connections. You won't be able to use try & catch to handle asynchronously thrown errors within MongoClient code.
const {MongoClient} = require("mongodb");
process.on("uncaughtException", (err) => {
console.log("process err", err);
process.exit(1)
})
async function run () {
let db;
try {
// connection url will throw because password isn't provided
db = await MongoClient.connect("mongodb://myUsername:#localhost", { useNewUrlParser: true });
} catch (err) {
console.log('Exiting from thrown error', err);
process.exit(1);
}
}
run();
Here's a simplified example of what's happening -- the error will end up "uncaught" and caught by the uncaughtException handler
process.on("uncaughtException", (err) => console.log("uncaught", err));
try {
setTimeout(() => {
throw new Error("asynchronously thrown error");
})
} catch (err) {
console.log("Error will not be caught here")
}
When I was using mongo version 3.6.1, it was not an issue and i was able to handle the thrown exception using catch. But after a few days on another project this type of error occurred and was showing as the error thrown from
%project_folder%/node_modules/mongodb/lib/utils.js:668
(Don't mind about the slash in the path string.)
The mongodb version this time is 3.6.3. Upon checking the code in that file at the mentioned line I found the below piece of code. where the caught error is again being thrown.
fn(function(err, res) {
if (err != null) {
try {
callback(err);
} catch (error) {
return process.nextTick(() => {
throw error;
});
}
return;
}
callback(err, res);
});
I changed the throw error to console.error(error) and the problem got resolved. But still you need to be caught somewhere in our code where connect function is called.
I think this is because the above piece of code is checking for the presence of error and passing it to the callback function and then again throwing the same error again. I suppose it is the MongoDB driver developer community's responsibility to resolve this issue.
I have a NodeJs application running in the following directory
First Application's Path '/users/user1/projects/sampleProject' which is running at 3000 port.
Second Application's Path '/users/user1/demoProjects/demo1' which is going to run at 5000 port on triggering the router function from first application.
The second NodeJs application is not yet started(It will run at port 5000). It need to run independently on hitting a router function in the first NodeJs Application which is running on port 3000 ie(http://localhost:3000/server/startServer). I'm new to NodeJs child processes, Kindly correct me if i'm wrong. And suggest me a right way to do it. Thanks
Start another node application using node.js?
I have tried it like below
// First NodeJs application
import { exec } from "child_process";
router.get('/startServer', async (req, res, next) => {
console.log("Initiated request")
let startServerInstance = 'cd "/users/user1/demoProjects/demo1" && npm run dev'; // path for the second NodeJs application
console.log("Server instance path => " + startServerInstance)
try {
// exec from child process, Spawns a shell then executes the command within that shell
let child = exec(startServerInstance, function (err, stdout, stderr) {
if (err) throw err;
else {
console.log("result ")
res.json({
status: 'success'
});
}
});
} catch (error) {
res.json({
status: 'error',
message: error
});
}
});
The above code executes the command and triggered the second application to run in background but it doesn't return anything. Either error or success result.
You need to use stout and stderror to check other server logs. Also your code is not correct. If you use if without {} it will not go to else statement. That is why you don't see 'result' text in console.
import {
exec
} from "child_process";
router.get('/startServer', async (req, res, next) => {
console.log("Initiated request")
let startServerInstance = 'cd "/users/user1/demoProjects/demo1" && npm run dev'; // path for the second NodeJs application
console.log("Server instance path => " + startServerInstance)
try {
// exec from child process, Spawns a shell then executes the command within that shell
let child = exec(startServerInstance, function(err) {
if (err) throw err;
console.log("Server started");
});
child.stdout.on('data', (data) => {
// this is new server output
console.log(data.toString());
});
child.stderr.on('data', (data) => {
// this is new server error output
console.log(data.toString());
});
res.json({
status: 'success'
});
} catch (error) {
res.json({
status: 'error',
message: error
});
}
});
Child process callback is only called once the process terminates. If the process keeps running, callback is not triggered.
Explained here - https://nodejs.org/docs/latest-v10.x/api/child_process.html#child_process_child_process_exec_command_options_callback
I want to use forever-monitor package to send me an email when my server crashes.
By going to the homepage I can see that an error is created and my server is restarted after the error. But I want to be able to capture these events (restart and error) so that I can log and send warning emails. But my debugger doesn't stop on error and restart events. Also, those console messages aren't printed.
I run it from command line as node myfilename.js, app.js is my main file.
Thanks for the help !
var forever = require('forever-monitor');
var child = new (forever.Monitor)('app.js', {
max: 3,
silent: false,
args: [],
});
child.on('error', function (err) {
console.log('An error occured '+err);
});
child.on('restart', function() {
console.log('Restarting file');
});
child.start();
setTimeout(function () {
throw new Error('I created an error');
}, 200);
In my application i want to create own module to capture my application error using uncaughtException.If i create uncaughtException in same module means its capturing errors but if i create that uncaughtException in separate module.Then call that module means its not capturing erros.Can anyone help me to fix this issue.
module1.js
var errorModule=require('./module2');
var err = new Error('Something went terribly wrong');
errorModule.captureError(err);
module2.js
module.exports.captureError=function(err){
process.on('uncaughtException', function(err) {
console.log(err);
});
}
Try this:
// module1.js
var errorModule=require('./module2');
errorModule.captureErrors();
throw Error('Something went terribly wrong');
// module2.js
module.exports.captureErrors = function() {
process.on('uncaughtException', function(err) {
console.log('an error occurred', err);
});
};
A few things to notice:
process.on('uncaughtException', ...) installs an event handler to catch uncaught exceptions; your code tries to pass an error to it, but that seems to defeat what you're writing ('to capture my application error using uncaughtException');
Uncaught exceptions are errors which are thrown (throw Error(...));
If you want the code in your module1 to work, module2 needs to look like this:
module.exports.captureError = function(err) {
console.log(err);
};
But that has nothing to do with uncaughtException.