Develop Reference

How to make an HTTP/HTTPS request within a Node.js server?

I'm just starting to learn Node.js and right now, I'm trying to use a Node.js Application through cPanel to provide a JSON response when its app's URL is accessed.
When visiting the app's URL, it's evident that the Node.js server is working as it should. So after editing the main JS file, and restarting the Node.js app, changes are reflected when visiting the URL again.
My problem:
Within the function of https.createServer( function (req, res) {});, I want to make an HTTPS request to a PHP file elsewhere, which returns a JSON response. At the moment, I can't even get a response or error from any type of request with the PHP file.
var https = require('https');
var server = https.createServer(function (req, res) {
var message = "";
res.writeHead(200, {
'Content-Type': 'text/plain'
});
var options = {
host: "mydomain.com",
path: '/myPhpScript.php'
};
https.get(options, function(res) {
var bodyChunks = [];
res.on('data', function(chunk) {
bodyChunks.push(chunk);
}).on('end', function() {
var body = Buffer.concat(bodyChunks);
message += body;
})
}).on('error', function(e) {
message += e;
});
res.end(message);
});
server.listen();
As you can see, message would be what's displayed to the browser window, but it's empty. Nothing appears when visiting the App URL. Is it possible to make an HTTPS request with a Node.js HTTPS server?
Note:
I've also tried with native-request and axios and have experienced the same issue.

Server code:
var http = require('http');
var https = require("https");
var server = http.createServer(function (req, res) {
let call = new Promise((resolve, reject) => {
var options = {
host: "jarrenmorris.com",
port: 443,
path: '/gamesense/r6_db/1.json'
};
https.get(options, function (res) {
var bodyChunks = [];
res.on('data', function (chunk) {
bodyChunks.push(chunk);
}).on('end', function () {
resolve(Buffer.concat(bodyChunks));
});
}).on('error', function (e) {
reject(e);
});
});
call.then((data) => {
// do something here with the successful request/json
res.writeHead(200, {
'Content-Type': 'text/plain'
});
res.end(data);
}).catch((err) => {
// do something here with the failure request/json
// res.write("ERROR:");
res.end(err);
});
});
server.listen(8081, "127.0.0.1", () => {
console.log(`Server listen on ${server.address().address}:${server.address().port} `);
});
Response:
{"name":"tim","age":"42"}
First thing i noticed, while i tried to run your code was, you cant establish a connection to your node.js.
The reason for this was you use the https module, but didnt specify an certificates/keyfiles. Skip this, and work with http till you get the result you want.
Then i wrapped you https request to the external api/file in a promise.
This allows a simple chaining and better readability of the code.
When the promises resolves/fullfill, we answer the request on the http server with the data we received from the external request.
The res.end in your code (where you put it) made no sense, since you didnt wait for the external request to complete. Thats the reason why its nothing is shown in the browser window.

Node proxy server modify response after query in database

I am troubling with nodejs proxy server modified(write) response.
I want to achieve auto login for one site via node proxy server and for that i have to query in database then i can modified response but it seems req ended before req.write and getting Error: write after end
Below is my implementation so far.
var express = require('express');
var proxy = require('http-proxy-middleware');
var options = {
target: 'http://example.com/', // target host
changeOrigin: true,
onProxyReq: function onProxyReq(proxyReq, req, res) {
var _write = res.write;
var body = "";
proxyReq.on('data', function(data) {
data = data.toString('utf-8');
body += data;
});
res.write = function (data) {
try{
//I have database query here instead of setTimeout
setTimeout(function(){
/* Modified response here and write */
_write.call(res, data); //can't write because req already end
},3000);
} catch (err) {
console.log('err',err);
}
}
}
}
// create the proxy (without context)
var exampleProxy = proxy(options);
// mount `exampleProxy` in web server
var app = express();
app.use('/', exampleProxy);
app.listen(8080);
Can anyone guide me how to achieve this ?

Express promise chain error

I've written a simple express.js server that handles REST API requests and fetches data from a MongoDB database. When I make a GET request to a specific endpoint ("localhost:8081/api/getUserData"), the promise chain doesn't work the way I want it to, and I still don't understand.
This is the error I get:
"[TypeError: Cannot read property 'db' of undefined]"
var MongoClient = require('mongodb').MongoClient;
var express = require('express');
var app = express();
var rp = require("request-promise");
var cors = require('cors');
// use it before all route definitions
app.use(cors({ origin: '*' }));
/********************** REST API FUNCTIONS **********************/
app.get('/api/getUserData', function (req, res, next) {
var context = {};
console.log("in api getUserData")
context.db_url = 'mongodb://localhost:27017/test';
openDatabaseConnection(context)
.then(getAllUserLocations)
.then(closeDatabaseConnection)
.then(function (context) {
res.send(context.userLocations)
})
.catch(function (error) {
console.log("ERROR :");
console.log(error);
})
})
/********************** END REST API FUNCTIONS **********************/
function getAllUserLocations(context) {
context.db.collection("test").find().toArray().then(function (err, result) {
console.log("Received from db: " + result.length + " objects");
context.userLocations = result;
return context;
});
}
function openDatabaseConnection(context) {
console.log("Opening DB connection...");
return MongoClient.connect(context.db_url)
.then(function (db) {
console.log("DB connection opened.");
context.db = db;
return context;
})
}
function closeDatabaseConnection(context) {
console.log("Closing DB connection");
return context.db.close()
.then(function () {
console.log("DB connection closed");
return context;
})
}
/********************** STARTING SERVER **********************/
var server = app.listen(8081, function () {
var host = server.address().address
var port = server.address().port
console.log("Githex server listening at http://%s:%s", host, port)
})
Any help would be appreciated, and even more with an explanation because I don't understand what I've done wrong.
Thanks!

Just like #adeneo mentioned on the first comment, you are missing the db property. Look at your first function:
app.get('/api/getUserData', function (req, res, next) {
var context = {};
console.log("in api getUserData")
context.db_url = 'mongodb://localhost:27017/test';
openDatabaseConnection(context)
.then(getAllUserLocations)
.then(closeDatabaseConnection)
.then(function (context) {
res.send(context.userLocations)
})
.catch(function (error) {
console.log("ERROR :");
console.log(error);
})
});
Now going through the lines within this function:
You setup context as an empty object
You added a db_url property onto the object, so far you have
context = {db_url: "mongodb://localhost:27017/test}
You pass the context object into the openDatabaseConnection function
Within the openDatabaseConnection function, you return a context object. This new returned object doesn't get set anywhere, it just gets returned and never used. You want to call the getuserlocation() function with that returned value.
So instead of just calling
.then(getAllUserConnection)
I would do
.then(function(context){getAllUserConnection(context);})
That should make use of the returned value and make sure you are using it.

How to have express handle and capture my errors

var database = require('database');
var express = require('express');
var app = express();
var cors = require('cors');
app.use(cors());
var bodyParser = require('body-parser');
var urlencodedParser = bodyParser.urlencoded({
extended: false
});
app.post('/dosomething', urlencodedParser, function(req, res) {
if (!req.body.a) {
res.status(500).send(JSON.stringify({
error: 'a not defined'
}));
return;
}
firstAsyncFunction(req.body.a, function(err, result) {
if (err) {
res.status(500).send('firstAsyncFunction was NOT a success!');
} else {
if (result.b) {
secondAsyncFunction(result.b, function(err, data) {
if (err) {
res.status(500).send('secondAsyncFunction was NOT a success!');
return;
}
res.send('EVERYTHING WAS A SUCCESS! ' + data);
});
}
else {
res.status(500).send('result.b is not defined');
}
}
});
});
function firstAsyncFunction(param, callback) {
//Some network call:
// Return either return (callback(null,'success')); or return (callback('error'));
var query = database.createQuery(someOptionsHere);
database.runDatabaseQuery(query, function(err, entities, info) {
if (err) {
return (callback('error'));
}
return (callback(null, 'success'));
});
};
function secondAsyncFunction(param, callback) {
//Some network call:
// Return either return (callback(null,'success')); or return (callback('error'));
var query = database.createQuery(someOptionsHere);
database.runDatabaseQuery(query, function(err, entities, info) {
if (err) {
return (callback('error'));
}
return (callback(null, 'success'));
});
};
var server = app.listen(process.env.PORT || 3000, function() {
var host = server.address().address;
var port = server.address().port;
console.log('App listening at http://%s:%s', host, port);
});
module.exports = app;
I have here a basic express http server. This server has one route, dosomething, which makes two network calls and tells the user if they were a success or not.
This is my entire webserver (this is a bare bones server of my actual server for example purposes). I am now concerned with this server crashing. Reading the docs for express I see there is a default error handler which will catch errors and prevent the server from crashing (http://expressjs.com/en/guide/error-handling.html). I have added the code:
function defaultErrorHandler(err, req, res, next) {
if (res.headersSent) {
return next(err);
}
res.status(500);
res.render('error', { error: err });
}
app.use(defaultErrorHandler);
This still crashes my server though. For example. I had a problem with my database returning an improper JSON response and inside of my firstAsyncFunction (not shown in the code) I tried to parse the JSON and it caused an error telling me it was improper JSON and the server crashed and was unable to take requests anymore until I restarted it. I would like to avoid this and have the default error handler send out a generic response back to the user when this occurs. I thought if I specified the defaultErrorHandler and put it inside of app.use that it would capture and handle all errors, but this does not seem to be the case? Inside of my async function for example you can see I am looking if an error was returned and if it was I send an error back to the user, but what if some other error occurs, how can I get express to capture and handle this error for me?

The defaultErrorHandler cannot handle exceptions that are thrown inside asynchronous tasks, such as callbacks.
If you define a route like:
app.get('/a', function(req, res) {
throw new Error('Test');
});
An error will be thrown, and in this case defaultErrorHandler will successfully catch it.
If the same exception occurs in an async manner, like so:
app.get('/a', function(req, res) {
setTimeout(function () {
throw new Error('Test');
}, 1000);
});
The server will crush, because the callback is actually in another context, and exceptions thrown by it will now be caught by the original catcher. This is a very difficult issue to deal with when it comes to callback.
There is more than one solution though. A possible solution will be to wrap every function that is prone to throw error with a try catch statement. This is a bit excessive though.
For example:
app.get('/a', function(req, res) {
setTimeout(function () {
try {
var x = JSON.parse('{');
}
catch (err) {
res.send(err.message);
}
}, 1000);
});
A nicer solution:
A nicer solution, would be to use promises instead, if it's possible, then for example you can declare a single errorHandler function like so:
function errorHandler(error, res) {
res.send(error.message);
}
Then, let's say you have to following function with fetches stuff from the database (I used setTimeout to simulate async behavior):
function getStuffFromDb() {
return new Promise(function (resolve, reject) {
setTimeout(function () {
resolve("{");
}, 100);
});
}
Notice that this function returns an invalid JSON string. Your route will look something like:
app.get('/a', function(req, res) {
getStuffFromDb()
.then(handleStuffFromDb)
.catch(function (error) { errorHandler(error, res) });
});
function handleStuffFromDb(str) {
return JSON.parse(str);
}
This is a very simplified example, but you can add a lot more functionality to it, and (at least theoretically) have a single catch statement which will prevent your server from crushing.

Node JS OR Express JS HTTP GET Request

I am using express.js and I need to make a call to HTTP GET request ,to fetch JSON data .Please suggest me some good node js/express js modules/lib to perform get/post request .

Node.js provides an extremely simple API for this functionality in the form of http.request.
var http = require('http');
//The url we want is: 'www.random.com/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
var options = {
host: 'www.random.com',
path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
callback = function(response) {
var str = '';
//another chunk of data has been recieved, so append it to `str`
response.on('data', function (chunk) {
str += chunk;
});
//the whole response has been recieved, so we just print it out here
response.on('end', function () {
console.log(str);
});
}
http.request(options, callback).end();
Here I attach some more examples with POST and custom headers. If you don't need special things, I'd stick to the native code.
Besides, Request, Superagent or Requestify are pretty good libraries to use.

var express = require('express');
var app = express();
var fs = require('fs');
app.get('/', function (req, res) {
fs.readFile('./test.json', 'utf8', function (err, data) {
if (err) {
res.send({error: err});
}
res.send(data);
})
});
var server = app.listen(3001, function () {
console.log('Example app listening port 3001');
});