I have a bunch of text files (I'm calling them 'index files' here) in a directory each containing a list of files separated by newlines.
In my NodeJS script I then want to iterate over these index files and make a call to tar using the index file as an input via the -T argument. For this I'm using spawnSync
What should happen is that tar then archives all of the files listed in the index file.
Instead what is happening is I get a completely empty archive, and no output.
Here is the relevant part of my script:
console.log("Processing index files");
process.chdir(sourcePath);
for(const key in indexFiles) {
let index = indexFiles[key];
console.log("Processing: "+index);
let commandLine = "tar acf "+outputPath+'/'+key+".tar.bz2 -T "+index;
console.log(process.cwd());
console.log(commandLine);
let tar = spawnSync("tar", ["acf", outputPath+"/"+key+".tar.bz2", "-T", index], {cwd:sourcePath, stdio:"inherit"});
}
In this script sourcePath is the location of the files listed within the index file. I'm setting that as the CWD since that is the way tar would work when I call it from the command line.
What's odd is that, as you can see, I am logging out both the sourcePath and the equivalent command line for my spawnSync call. So the output looks like this.
Processing index files
/media/chmo/NewLinux/scan/2022-03-22/temp
Processing: /media/chmo/NewLinux/wrangled/d01d36c8-698a-4791-9075-73fa4c0af881_0.txt
/media/chmo/NewLinux/scan/2022-03-22/temp
tar acf /media/chmo/NewLinux/wrangled/0.tar.bz2 -T /media/chmo/NewLinux/wrangled/d01d36c8-698a-4791-9075-73fa4c0af881_0.txt
I can literally take the second from last line, which should be the CWD for my call to spawnSync, cd into that directory, and then run the command as it appears in the last line, and that works perfectly. Yet when I do what should be the exact same operation but called from within NodeJS it simply creates an empty tar file.
What's up with that? Not sure how else to explain it. It seems like something very basic that just isn't working, so I'm hoping that I've just done something wrong and someone can point out what that is.
you dont need to changecwd like that, just pass it to 3rd arg of spawnSync.
spawnSync('tar', [args], { cwd: sourcePath })
I recommend using execSync over spawnSync in your situation, since you don't need any info other than output of tar command (which is empty on success).
I made little script that is close to your requirement, hope this helps you.
const fs = require('fs/promises')
const { execSync } = require('child_process')
const path = require('path')
const [, , indexfilePath] = process.argv
async function main() {
const indexFilesDir = path.resolve(indexfilePath)
const files = await fs.readdir(indexFilesDir, { withFileTypes: true })
for (const f of files) {
if (!f.isFile()) continue
console.log('processing index file', f.name)
const output = execSync(`tar -acf /tmp/node-${f.name}.tar.bz2 -T ${f.name}`, {
cwd: indexFilesDir,
// encoding: 'utf8',
})
console.log(`------> ${f.name} <------`)
process.stdout.write(output)
console.log(`------> end <------`)
}
}
main()
.then(() => {
console.log('completed main')
})
.catch(console.error)
above script tags index files dir and saves tar file in /tmp dir.
$ tree ./
.
├── cli.js
└── test
├── contents
│ ├── en.txt
│ └── fr.txt
└── index-1.txt
file content of index-1.txt index file.
$ cat test/index-1.txt
./contents/en.txt
./contents/fr.txt
usage
$ node cli.js ./test/
processing index file index-1.txt
------> index-1.txt <------
------> end <------
completed main
$ ls /tmp/
node-index-1.txt.tar.bz2
$ tar --list -f /tmp/node-index-1.txt.tar.bz2
./contents/en.txt
./contents/fr.txt
note: if you are using this inside of a webserver or other, use either exec or spawn with Promise wrap. Because sync operations blocks event loop of nodejs.
So I'm using the package esm and module-alias, but it seems like esm does not register module-alias's paths.
Here's how I'm loading my server file:
nodemon -r esm ./src/index.js 8081
Here's the top of my index.js file:
import "module-alias/register"
import "#/setup"
import "#/setup" does not work whereas require("#/setup") does.
The problem is that esm tries to handle all import statements when parsing the file, before any other module gets loaded.
When processing import statements, it uses node's builtin require rather than the modified require created by module-alias
To fix this, you need to first load module-alias and then esm. This way, module-alias will get the chance to modify the require function before esm gets to do anything.
You can achive this by passing multiple -r parameters to node, but make sure module-alias comes first:
node -r module-alias/register -r esm index.js 8081
or with nodemon:
nodemon -r module-alias/register -r esm ./src/index.js 8081
You also need to remove the import "module-alias/register" from your code, since now it's loaded from the command line.
For me worked the following code:
package.json
"scripts": {
"dev": "pkill -f lib/serverIndex.js; NODE_ENV=development node lib/serverIndex.js",
lib/serverIndex.js
require = require('esm')(module/*, options*/);
require('module-alias/register');
module.exports = require("./server.js");
This problem has been plaguing me for years because I want to write good quality code that is shared between node & browser.
I finally found a system that works:
Place 'nesm.js' in the root of your project
[optional] Place the 'nesm' shell script in your path, make it executable
Run scripts with: 'nesm file_to_run.js' or 'node path/to/nesm.js -- file_to_run.js'
'nesm.js'
/*
* esm and module-alias do not play nicely together.
* this precise arrangement is the only way I found to make it work.
* you can run this from anywhere in your project hierarchy.
* you can use args, and use in npm scripts.
* encourage the node.js devs to make this work natively. ux matters.
* ---- CAVEATS
* will not work with "type":"module"
* ---- SETUP
* place 'nesm.js' in the root of your project
* [optional] place the 'nesm' shell script in your path, make it executable
* ---- USAGE
* > nesm file_to_run.js
* to run without the nesm shell script:
* > node path/to/nesm.js -- file_to_run.js
* to run with nodemon:
* > nodemon -- path/to/nesm.js -- file_to_run.js
*/
require = require('esm')(module); // eslint-disable-line no-global-assign
require('module-alias/register'); // must come after esm for some reason
let runNext;
for(const arg of process.argv) {
if(runNext) {
let filename = arg;
if(filename[0]!='.' && filename[0]!='/') filename = './'+filename;
require(filename);
break;
}
runNext = (arg=='--');
}
'nesm' shell script
#!/bin/bash
if [ -z $1 ]; then
echo "Node esm runner. Usage: nesm file_to_run.js"
exit 1
fi
baseDir=$( pwd )
while [ ! -f "$baseDir/nesm.js" ]; do
if [ ${#baseDir} -le 1 ]; then
echo "nesm.js not found in folder ancestry"
exit 1
fi
baseDir="$(dirname "$baseDir")"
done
file1=$(realpath $1);
node $baseDir/nesm.js -- $file1
There is another solution, initially found in this comment to solve the problem without even using module-alias.
I also made a repo to simplify this, check it here esm-module-alias
Any ideas on how I could implement an auto-reload of files in Node.js? I'm tired of restarting the server every time I change a file.
Apparently Node.js' require() function does not reload files if they already have been required, so I need to do something like this:
var sys = require('sys'),
http = require('http'),
posix = require('posix'),
json = require('./json');
var script_name = '/some/path/to/app.js';
this.app = require('./app').app;
process.watchFile(script_name, function(curr, prev){
posix.cat(script_name).addCallback(function(content){
process.compile( content, script_name );
});
});
http.createServer(this.app).listen( 8080 );
And in the app.js file I have:
var file = require('./file');
this.app = function(req, res) {
file.serveFile( req, res, 'file.js');
}
But this also isn't working - I get an error in the process.compile() statement saying that 'require' is not defined. process.compile is evaling the app.js, but has no clue about the node.js globals.
A good, up to date alternative to supervisor is nodemon:
Monitor for any changes in your node.js application and automatically restart the server - perfect for development
To use nodemon with version of Node without npx (v8.1 and below, not advised):
$ npm install nodemon -g
$ nodemon app.js
Or to use nodemon with versions of Node with npx bundled in (v8.2+):
$ npm install nodemon
$ npx nodemon app.js
Or as devDependency in with an npm script in package.json:
"scripts": {
"start": "nodemon app.js"
},
"devDependencies": {
"nodemon": "..."
}
node-supervisor is awesome
usage to restart on save for old Node versions (not advised):
npm install supervisor -g
supervisor app.js
usage to restart on save for Node versions that come with npx:
npm install supervisor
npx supervisor app.js
or directly call supervisor in an npm script:
"scripts": {
"start": "supervisor app.js"
}
i found a simple way:
delete require.cache['/home/shimin/test2.js']
If somebody still comes to this question and wants to solve it using only the standard modules I made a simple example:
var process = require('process');
var cp = require('child_process');
var fs = require('fs');
var server = cp.fork('server.js');
console.log('Server started');
fs.watchFile('server.js', function (event, filename) {
server.kill();
console.log('Server stopped');
server = cp.fork('server.js');
console.log('Server started');
});
process.on('SIGINT', function () {
server.kill();
fs.unwatchFile('server.js');
process.exit();
});
This example is only for one file (server.js), but can be adapted to multiple files using an array of files, a for loop to get all file names, or by watching a directory:
fs.watch('./', function (event, filename) { // sub directory changes are not seen
console.log(`restart server`);
server.kill();
server = cp.fork('server.js');
})
This code was made for Node.js 0.8 API, it is not adapted for some specific needs but will work in some simple apps.
UPDATE:
This functional is implemented in my module simpleR, GitHub repo
nodemon came up first in a google search, and it seems to do the trick:
npm install nodemon -g
cd whatever_dir_holds_my_app
nodemon app.js
nodemon is a great one. I just add more parameters for debugging and watching options.
package.json
"scripts": {
"dev": "cross-env NODE_ENV=development nodemon --watch server --inspect ./server/server.js"
}
The command: nodemon --watch server --inspect ./server/server.js
Whereas:
--watch server Restart the app when changing .js, .mjs, .coffee, .litcoffee, and .json files in the server folder (included subfolders).
--inspect Enable remote debug.
./server/server.js The entry point.
Then add the following config to launch.json (VS Code) and start debugging anytime.
{
"type": "node",
"request": "attach",
"name": "Attach",
"protocol": "inspector",
"port": 9229
}
Note that it's better to install nodemon as dev dependency of project. So your team members don't need to install it or remember the command arguments, they just npm run dev and start hacking.
See more on nodemon docs: https://github.com/remy/nodemon#monitoring-multiple-directories
Nodemon has been the go to for restarting server for file changes for long time. Now with Node.js 19 they have introduced a --watch flag, which does the same [experimental]. Docs
node --watch index.js
node-dev works great. npm install node-dev
It even gives a desktop notification when the server is reloaded and will give success or errors on the message.
start your app on command line with:
node-dev app.js
There is Node-Supervisor that you can install by
npm install supervisor
see http://github.com/isaacs/node-supervisor
You can use nodemon from NPM.
And if you are using Express generator then you can using this command inside your project folder:
nodemon npm start
or using Debug mode
DEBUG=yourapp:* nodemon npm start
you can also run directly
nodemon your-app-file.js
Hope this help.
There was a recent (2009) thread about this subject on the node.js mailing list. The short answer is no, it's currently not possible auto-reload required files, but several people have developed patches that add this feature.
With Node.js 19 you can monitor file changes with the --watch option. After a file is changed, the process is restarted automatically, reflecting new changes.
node --watch server.js
yet another solution for this problem is using forever
Another useful capability of Forever is that it can optionally restart
your application when any source files have changed. This frees you
from having to manually restart each time you add a feature or fix a
bug. To start Forever in this mode, use the -w flag:
forever -w start server.js
Here is a blog post about Hot Reloading for Node. It provides a github Node branch that you can use to replace your installation of Node to enable Hot Reloading.
From the blog:
var requestHandler = require('./myRequestHandler');
process.watchFile('./myRequestHandler', function () {
module.unCacheModule('./myRequestHandler');
requestHandler = require('./myRequestHandler');
}
var reqHandlerClosure = function (req, res) {
requestHandler.handle(req, res);
}
http.createServer(reqHandlerClosure).listen(8000);
Now, any time you modify myRequestHandler.js, the above code will notice and replace the local requestHandler with the new code. Any existing requests will continue to use the old code, while any new incoming requests will use the new code. All without shutting down the server, bouncing any requests, prematurely killing any requests, or even relying on an intelligent load balancer.
I am working on making a rather tiny node "thing" that is able to load/unload modules at-will (so, i.e. you could be able to restart part of your application without bringing the whole app down).
I am incorporating a (very stupid) dependency management, so that if you want to stop a module, all the modules that depends on that will be stopped too.
So far so good, but then I stumbled into the issue of how to reload a module. Apparently, one could just remove the module from the "require" cache and have the job done. Since I'm not keen to change directly the node source code, I came up with a very hacky-hack that is: search in the stack trace the last call to the "require" function, grab a reference to it's "cache" field and..well, delete the reference to the node:
var args = arguments
while(!args['1'] || !args['1'].cache) {
args = args.callee.caller.arguments
}
var cache = args['1'].cache
util.log('remove cache ' + moduleFullpathAndExt)
delete( cache[ moduleFullpathAndExt ] )
Even easier, actually:
var deleteCache = function(moduleFullpathAndExt) {
delete( require.cache[ moduleFullpathAndExt ] )
}
Apparently, this works just fine. I have absolutely no idea of what that arguments["1"] means, but it's doing its job. I believe that the node guys will implement a reload facility someday, so I guess that for now this solution is acceptable too.
(btw. my "thing" will be here: https://github.com/cheng81/wirez , go there in a couple of weeks and you should see what I'm talking about)
solution at:
http://github.com/shimondoodkin/node-hot-reload
notice that you have to take care by yourself of the references used.
that means if you did : var x=require('foo'); y=x;z=x.bar; and hot reloaded
it.
it means you have to replace the references stored in x, y and z. in the hot reaload callback function.
some people confuse hot reload with auto restart
my nodejs-autorestart module also has upstart integration to enable auto start on boot.
if you have a small app auto restart is fine, but when you have a large app hot reload is more suitable. simply because hot reload is faster.
Also I like my node-inflow module.
Here's a low tech method for use in Windows. Put this in a batch file called serve.bat:
#echo off
:serve
start /wait node.exe %*
goto :serve
Now instead of running node app.js from your cmd shell, run serve app.js.
This will open a new shell window running the server. The batch file will block (because of the /wait) until you close the shell window, at which point the original cmd shell will ask "Terminate batch job (Y/N)?" If you answer "N" then the server will be relaunched.
Each time you want to restart the server, close the server window and answer "N" in the cmd shell.
my app structure:
NodeAPP (folder)
|-- app (folder)
|-- all other file is here
|-- node_modules (folder)
|-- package.json
|-- server.js (my server file)
first install reload with this command:
npm install [-g] [--save-dev] reload
then change package.json:
"scripts": {
"start": "nodemon -e css,ejs,js,json --watch app"
}
now you must use reload in your server file:
var express = require('express');
var reload = require('reload');
var app = express();
app.set('port', process.env.PORT || 3000);
var server = app.listen(app.get('port'), function() {
console.log( 'server is running on port ' + app.get('port'));
});
reload(server, app);
and for last change, end of your response send this script:
<script src="/reload/reload.js"></script>
now start your app with this code:
npm start
You can do it with browser-refresh. Your node app restarts automatically, your result page in browser also refreshes automatically. Downside is that you have to put js snippet on generated page. Here's the repo for the working example.
const http = require('http');
const hostname = 'localhost';
const port = 3000;
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/html; charset=UTF-8');
res.write('Simple refresh!');
res.write(`<script src=${process.env.BROWSER_REFRESH_URL}></script>`);
res.end();
})
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);
if (process.send) {
process.send({ event: 'online', url: `http://${hostname}:${port}/` })
}
});
Not necessary to use nodemon or other tools like that. Just use capabilities of your IDE.
Probably best one is IntelliJ WebStorm with hot reload feature (automatic server and browser reload) for node.js.
I have tried pm2 : installation is easy and easy to use too; the result is satisfying. However, we have to take care of which edition of pm2 that we want. pm 2 runtime is the free edition, whereas pm2 plus and pm2 enterprise are not free.
As for Strongloop, my installation failed or was not complete, so I couldn't use it.
If your talking about server side NodeJS hot-reloading, lets say you wish to have an Javascript file on the server which has an express route described and you want this Javascript file to hot reload rather than the server re-starting on file change then razzle can do that.
An example of this is basic-server
https://github.com/jaredpalmer/razzle/tree/master/examples/basic-server
The file https://github.com/jaredpalmer/razzle/blob/master/examples/basic-server/src/server.js will hot-reload if it is changed and saved, the server does not re-start.
This means you can program a REST server which can hot-reload using this razzle.
it's quite simple to just do this yourself without any dependency... the built in file watcher have matured enough that it dose not sucks as much as before
you don't need any complicated child process to spawn/kill & pipe std to in/out... you just need a simple web worker, that's all! A web Worker is also what i would have used in browsers too... so stick to web techniques! worker will also log to the console
import { watch } from 'node:fs/promises'
import { Worker } from 'node:worker_threads'
let worker = new Worker('./app.js')
async function reloadOnChange (dir) {
const watcher = watch(dir, { recursive: true })
for await (const change of watcher) {
if (change.filename.endsWith('.js')) {
worker.terminate()
worker = new Worker('./app.js')
}
}
}
// All the folder to watch for
['./src', './lib', './test'].map(reloadOnChange)
this might not be the best solution where you use anything else other than javascript and do not depend on some build process.
Use this:
function reload_config(file) {
if (!(this instanceof reload_config))
return new reload_config(file);
var self = this;
self.path = path.resolve(file);
fs.watchFile(file, function(curr, prev) {
delete require.cache[self.path];
_.extend(self, require(file));
});
_.extend(self, require(file));
}
All you have to do now is:
var config = reload_config("./config");
And config will automatically get reloaded :)
loaddir is my solution for quick loading of a directory, recursively.
can return
{ 'path/to/file': 'fileContents...' }
or
{ path: { to: { file: 'fileContents'} } }
It has callback which will be called when the file is changed.
It handles situations where files are large enough that watch gets called before they're done writing.
I've been using it in projects for a year or so, and just recently added promises to it.
Help me battle test it!
https://github.com/danschumann/loaddir
You can use auto-reload to reload the module without shutdown the server.
install
npm install auto-reload
example
data.json
{ "name" : "Alan" }
test.js
var fs = require('fs');
var reload = require('auto-reload');
var data = reload('./data', 3000); // reload every 3 secs
// print data every sec
setInterval(function() {
console.log(data);
}, 1000);
// update data.json every 3 secs
setInterval(function() {
var data = '{ "name":"' + Math.random() + '" }';
fs.writeFile('./data.json', data);
}, 3000);
Result:
{ name: 'Alan' }
{ name: 'Alan' }
{ name: 'Alan' }
{ name: 'Alan' }
{ name: 'Alan' }
{ name: '0.8272748321760446' }
{ name: '0.8272748321760446' }
{ name: '0.8272748321760446' }
{ name: '0.07935990858823061' }
{ name: '0.07935990858823061' }
{ name: '0.07935990858823061' }
{ name: '0.20851597073487937' }
{ name: '0.20851597073487937' }
{ name: '0.20851597073487937' }
another simple solution is to use fs.readFile instead of using require
you can save a text file contaning a json object, and create a interval on the server to reload this object.
pros:
no need to use external libs
relevant for production (reloading config file on change)
easy to implement
cons:
you can't reload a module - just a json containing key-value data
For people using Vagrant and PHPStorm, file watcher is a faster approach
disable immediate sync of the files so you run the command only on save then create a scope for the *.js files and working directories and add this command
vagrant ssh -c "/var/www/gadelkareem.com/forever.sh restart"
where forever.sh is like
#!/bin/bash
cd /var/www/gadelkareem.com/ && forever $1 -l /var/www/gadelkareem.com/.tmp/log/forever.log -a app.js
I recently came to this question because the usual suspects were not working with linked packages. If you're like me and are taking advantage of npm link during development to effectively work on a project that is made up of many packages, it's important that changes that occur in dependencies trigger a reload as well.
After having tried node-mon and pm2, even following their instructions for additionally watching the node_modules folder, they still did not pick up changes. Although there are some custom solutions in the answers here, for something like this, a separate package is cleaner. I came across node-dev today and it works perfectly without any options or configuration.
From the Readme:
In contrast to tools like supervisor or nodemon it doesn't scan the filesystem for files to be watched. Instead it hooks into Node's require() function to watch only the files that have been actually required.
const cleanCache = (moduleId) => {
const module = require.cache[moduleId];
if (!module) {
return;
}
// 1. clean parent
if (module.parent) {
module.parent.children.splice(module.parent.children.indexOf(module), 1);
}
// 2. clean self
require.cache[moduleId] = null;
};