Hi I have a rest api set up in Nodejs and the ajax call is working perfectly, that is until I try to call an external REST service from within the method.
Can anyone help me out to work out why this wont work? I'm using Nodejs with Express running on port 3000, basically localhost at the minute. Bellows my work in progress but its been changed alot. I was using the request module but now have went back to http.
app.get('/api/exchange', function (req, res){
var text = '';
var options = {
host : 'rate-exchange.appspot.com',
port : 3000,
path : '/currency?from=GBP&to=USD',
method : 'GET'
};
var call = http.request(options, function(res) {
console.log("statusCode: ", res.statusCode);
text = "made it in";
res.on('data', function(d) {
text = "here";
});
});
call.end();
call.on('error', function(e) {
text = "error";
});
res.json({ msg: text });
});
Excuse my classic javascript debuging technique, I'm basically just using text to see where its going.
When I run this I get the following back.
{
"msg": ""
}
p.s. anyone knows of any good debuging tools for node I'd be greatful.
I guess port:3000 is wrong. And you should get response from http.request callback function.
app.get('/', function (req, res){
var text = '';
var options = {
host : 'rate-exchange.appspot.com',
//port : 3000,
path : '/currency?from=GBP&to=USD',
method : 'GET'
};
var call = http.request(options, function(resp) {
console.log("statusCode: ", res.statusCode);
text = "made it in";
resp.on('data', function(d) {
text = "here";
console.log("response data: "+d);
});
});
call.end();
call.on('error', function(e) {
text = "error";
});
//res.json({ msg: text });
});
Related
I'll try to make this as simple as possible so i'm not having to post a ton of code. Heres what my app does right now:
User uploads an audio file from the browser
That file is processed on my server, this process takes some time and has about 8 or so steps to complete.
Once everything is finished, the user gets feedback in the browser that the process is complete.
What I want to add to this, is after every step in the process that is completed, send some data back to the server. For example: "Your file is uploaded", "Meta data processed", "image extracted" etc etc so the user gets incremental feedback about what is happening and I believe Server Sent Events can help me do this.
Currently, the file is POSTed to the server with app.post('/api/track', upload.single('track'), audio.process). audio.process is where all the magic happens and sends the data back to the browser with res.send(). Pretty typical.
While trying to get the events working, I have implemented this function
app.get('/stream', function(req, res) {
res.sseSetup()
for (var i = 0; i < 5; i++) {
res.sseSend({count: i})
}
})
and when the user uploads a file from the server I just make a call to this route and register all the necessary events with this function on the client side:
progress : () => {
if (!!window.EventSource) {
const source = new EventSource('/stream')
source.addEventListener('message', function(e) {
let data = JSON.parse(e.data)
console.log(e);
}, false)
source.addEventListener('open', function(e) {
console.log("Connected to /stream");
}, false)
source.addEventListener('error', function(e) {
if (e.target.readyState == EventSource.CLOSED) {
console.log("Disconnected from /stream");
} else if (e.target.readyState == EventSource.CONNECTING) {
console.log('Connecting to /stream');
}
}, false)
} else {
console.log("Your browser doesn't support SSE")
}
}
this works as expected, when I upload a track, i get a stream of events counting from 0-4. So thats great!
My Problem/Question: How do i send relevant messages from the audio.process route, to the /stream route so that the messages can be related to whats happening. audio.process has to be a POST, and /stream has to be a GET with the header 'Content-Type': 'text/event-stream'. It seems kind of weird to make GET requests from within audio.process but is this the best way?
Any and all advice/tips are appreciated! Let me know if you need any more info.
New Answer:
Just use socket.io, it's so much easier and better!
https://www.npmjs.com/package/socket.io#in-conjunction-with-express
basic setup:
const express = require('express');
const PORT = process.env.PORT || 5000;
const app = express();
const server = require('http').createServer(app);
const io = require('socket.io')(server);
// listen to socket connections
io.on('connection', function(socket){
// get that socket and listen to events
socket.on('chat message', function(msg){
// emit data from the server
io.emit('chat message', msg);
});
});
// Tip: add the `io` reference to the request object through a middleware like so:
app.use(function(request, response, next){
request.io = io;
next();
});
server.listen(PORT);
console.log(`Listening on port ${PORT}...`);
and in any route handler, you can use socket.io:
app.post('/post/:post_id/like/:user_id', function likePost(request, response) {
//...
request.io.emit('action', 'user liked your post');
})
client side:
<script src="/socket.io/socket.io.js"></script>
<script src="https://code.jquery.com/jquery-1.11.1.js"></script>
<script>
$(function () {
var socket = io();
$('form').submit(function(e){
e.preventDefault(); // prevents page reloading
socket.emit('chat message', $('#m').val());
$('#m').val('');
return false;
});
socket.on('chat message', function(msg){
$('#messages').append($('<li>').text(msg));
});
});
</script>
full example: https://socket.io/get-started/chat/
Original Answer
Someone (user: https://stackoverflow.com/users/451634/benny-neugebauer | from this article: addEventListener on custom object) literally gave me a hint on how to implement this without any other package except express! I have it working!
First, import Node's EventEmitter:
const EventEmitter = require('events');
Then create an instance:
const Stream = new EventEmitter();
Then create a GET route for event streaming:
app.get('/stream', function(request, response){
response.writeHead(200, {
'Content-Type': 'text/event-stream',
'Cache-Control': 'no-cache',
'Connection': 'keep-alive'
});
Stream.on("push", function(event, data) {
response.write("event: " + String(event) + "\n" + "data: " + JSON.stringify(data) + "\n\n");
});
});
In this GET route, you are writing back that the request is 200 OK, content-type is text/event-stream, no cache, and to keep-alive.
You are also going to call the .on method of your EventEmitter instance, which takes 2 parameters: a string of the event to listen for and a function to handle that event(that function can take as much params as it is given)
Now.... all you have to do to send a server event is to call the .emit method of your EventEmitter instance:
Stream.emit("push", "test", { msg: "admit one" });
The first parameter is a string of the event you want to trigger (make sure that it is the same as the one in the GET route). Every subsequent parameter to the .emit method will be passed to the listener's callback!
That is it!
Since your instance was defined in a scope above your route definitions, you can call the .emit method from any other route:
app.get('/', function(request, response){
Stream.emit("push", "test", { msg: "admit one" });
response.render("welcome.html", {});
});
Thanks to how JavaScript scoping works, you can even pass that EventEmitter instance around to other function, even from other modules:
const someModule = require('./someModule');
app.get('/', function(request, response){
someModule.someMethod(request, Stream)
.then(obj => { return response.json({}) });
});
In someModule:
function someMethod(request, Stream) {
return new Promise((resolve, reject) => {
Stream.emit("push", "test", { data: 'some data' });
return resolve();
})
}
That easy! No other package needed!
Here is a link to Node's EventEmitter Class: https://nodejs.org/api/events.html#events_class_eventemitter
My example:
const EventEmitter = require('events');
const express = require('express');
const app = express();
const Stream = new EventEmitter(); // my event emitter instance
app.get('/stream', function(request, response){
response.writeHead(200, {
'Content-Type': 'text/event-stream',
'Cache-Control': 'no-cache',
'Connection': 'keep-alive'
});
Stream.on("push", function(event, data) {
response.write("event: " + String(event) + "\n" + "data: " + JSON.stringify(data) + "\n\n");
});
});
setInterval(function(){
Stream.emit("push", "test", { msg: "admit one" });
}, 10000)
UPDATE:
i created a module/file that is easier to use and doesn't cause memory leaks!
const Stream = function() {
var self = this;
// object literal of connections; IP addresses as the key
self.connections = {};
self.enable = function() {
return function(req, res, next) {
res.sseSetup = function() {
res.writeHead(200, {
'Content-Type': 'text/event-stream',
'Cache-Control': 'no-cache',
'Connection': 'keep-alive'
})
}
res.sseSend = function(id, event, data) {
var stream = "id: " + String(id) + "\n" +
"event: " + String(event) + "\n" +
"data: " + JSON.stringify(data) +
"\n\n";
// console.log(id, event, data, stream);
res.write(stream);
}
next()
}
}
self.add = function(request, response) {
response.sseSetup();
var ip = String(request.ip);
self.connections[ip] = response;
}.bind(self);
self.push_sse = function(id, type, obj) {
Object.keys(self.connections).forEach(function(key){
self.connections[key].sseSend(id, type, obj);
});
}.bind(self);
}
/*
Usage:
---
const express = require('express');
const Stream = require('./express-eventstream');
const app = express();
const stream = new Stream();
app.use(stream.enable());
app.get('/stream', function(request, response) {
stream.add(request, response);
stream.push_sse(1, "opened", { msg: 'connection opened!' });
});
app.get('/test_route', function(request, response){
stream.push_sse(2, "new_event", { event: true });
return response.json({ msg: 'admit one' });
});
*/
module.exports = Stream;
Script located here - https://github.com/ryanwaite28/script-store/blob/master/js/express-eventstream.js
I am trying to retrieve data from a REST API in the server side (.js) and display it in my view (.jade)
I was able to get the data but was not able to send it to the view .
This is how my code looks like :
var BugData ='initial data' ;
var https = require('https');
var optionsget = {
rejectUnauthorized: false,
host : 'My host', // here only the domain name
// (no http/https !)
port : 443,
path : 'Mypath', // the rest of the url with parameters if needed
method : 'GET' // do GET
};
console.info('Options prepared:');
console.info(optionsget);
console.info('Do the GET call');
// do the GET request
var reqGet = https.request(optionsget, function(res) {
console.log("statusCode: ", res.statusCode);
res.on('data', function(d) {
console.info('GET result:\n');
BugData =d;
console.log('Show Data : ***** \n' +d);
});
});
reqGet.end();
reqGet.on('error', function(e) {
console.error(e);
});
res.render('index', { ab:BugData});
BugData (was defined before )is the variable i am trying to send to the view but for some reasons it is empty and does not contain the variable 'd'
Does anyone know why or how can i solve this ?
Thanks
There is no need to write that long code.
Be simple, follow these steps:
1) install request package:
npm install --save request
2) outside of router add:
var request = require('request');
process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0;
3) use this code inside router:
request.get({url: 'https://my-host/Mypath'}, function(err, response, body) {
var data = {};
if (err) {
console.error(err);
data.err = err;
}
data.ab = body;
console.log('Data: ', data);
res.render('index', data);
});
I know how http request works and I know how to send and receive response.
This is the sample code of http request.
var http = require('http');
var options = {
host: 'www.nodejitsu.com',
path: '/',
port: '1337',
method: 'POST'
};
callback = function(response) {
var str = ''
response.on('data', function (chunk) {
str += chunk;
});
response.on('end', function () {
console.log(str);
});
}
var req = http.request(options, callback);
req.write("hello world!");
req.end();
In my site everything working fine Server B send request to server A and server A response to server B. But, one time I face a problem when there is huge no of traffic on server A and it was unable to receive any request from server B which halt the whole process.
So is there is any error block in request to handle this type of errors ?
I googled alot and try this type of foolish things but it does not work for me
callback = function(response,error) {
if(error){
console.log(error)
}else{
var str = ''
response.on('data', function (chunk) {
str += chunk;
});
response.on('error', function (err) {
console.log(err);
});
}
});
Have you tried this:
var req = http.request(options,callback);
req.on('error', function(e) {
console.log('problem with request: ' + e.message);
});
as given here:
http://nodejs.org/api/http.html#http_http_request_options_callback
Im using sailsjs as a MVC for node js, i'm still learning it.
I managed to get data from my own database and use it.
But now i need/want to get data from an external rest api.
I used this in my controller:
// api/controllers/SomeController.js
test : function(res,req){
var j;
var https = require('https');
var options = {
hostname: 'testing.atlassian.net',
port: 443,
path: '/rest/api/2/search?jql=project=ABC',
method: 'GET',
headers: {'Authorization': 'Basic ' + 'SuperSecretLoginAndPassword'}
};
var req = https.request(options, function(res) {
res.setEncoding('utf8');
res.on('data', function(d) {
});
});
req.end();
}
The variable d is displaying the right result.
How can i use the request results in my view?
I've searched a lot but i cant find any ways to display this in my view.
And will this be realtime updated? So if something in de rest api changes I won't have to refresh.
Sorry if this is something stupid.
Basically you'll want to wait for your request to fire its callback and then feed the fetched data into res.locals. Assuming you are fetching JSON data, you could do this:
// api/controllers/SomeController.js
test: function(req, res) {
var https = require('https');
...
https.request(options, function(response) {
var responseData = '';
response.setEncoding('utf8');
response.on('data', function(chunk){
responseData += chunk;
});
response.once('error', function(err){
// Some error handling here, e.g.:
res.serverError(err);
});
response.on('end', function(){
try {
// response available as `responseData` in `yourview`
res.locals.requestData = JSON.parse(responseData);
} catch (e) {
sails.log.warn('Could not parse response from options.hostname: ' + e);
}
res.view('yourview');
});
}).end();
}
The example code you supplied has some issues:
test: function(res,req) ... Don't mixup the controller arguments, the first is _req_uest, the second one _res_ponse.
var req = https.request ... You really do not want to override the req argument passed into your controller action. Use some other name.
https.request(options, function(res) {...} Same here. Doing this overrides res for the https.request callback scope - preventing you from using all the goodies (e.g.: res.view) supplied by the res parameter passed to your controller.
I'd guess it would make sense for you to read up on closures and callbacks:
What are Closures and Callbacks?
I am attempting to test drive an node.js application based on express. I want to return a simple 404.html, which I can successfully do, but afterward, calling close on the node http server gets this error:
Fatal error: Cannot call method 'call' of undefined
I am having a hard time tracking down what is undefined because the same method works beautifully when called elsewhere.
Here is my express code:
function Server() {
this.port = 9000;
this.staticDir = '/public';
}
function handleHomeRequest(req, res) {
var body = '<html><body>Home Page.</body></html>';
res.send(body);
}
Server.prototype.start = function () {
expServer = express();
expServer.get('/', function (req, res) { handleHomeRequest(req, res); });
expServer.use(function (req, res) {
res.status(404).sendfile('./src/public/404.html');
});
runningServer = expServer.listen(this.port);
};
Server.prototype.stop = function (cb) {
runningServer.close(cb);
};
Here is my nodeunit test code:
var ROOT_URL = 'http://localhost',
PORT = 9000,
URL = ROOT_URL + ':' + PORT + '/',
http = require('http'),
Server = require('./server.js'),
server;
exports.setUp = function(done) {
server = new Server();
done();
};
exports.tearDown = function (done) {
server = null;
done();
};
exports['Requesting a page that does not exist results in a 404.'] = function (test) {
server.start();
httpGet(URL + 'guaranteedNotToExistPage', function(res, data) {
test.equal(404, res.statusCode, 'Requesting a page that dne did not return with a status code of 404.');
test.ok(data.indexOf('404 Page Not Found') > -1, 'The 404 page was not returned.');
//test.done();
server.stop(test.done);
});
};
function httpGet(url, callback) {
var request = http.get(url),
receivedData = '';
request.on('response', function (response) {
response.setEncoding('utf8');
response.on('data', function (chunk) {
receivedData += chunk;
});
response.on('end', function () {
callback(response, receivedData);
});
});
}
The result of the http get request come back, the failure only occurs when I call server.stop(test.done); however, stopping the server is required to ensure my unit tests can be run in any order and independent.
First, where runningServer is defined? I can't see a
var runningServer;
anywhere in the first peace of code.
So, if you write a value in prototype.start I doubt you can access it on prototype.stop that is a different scope.
Second, {expressListener}.close() in node 0.6 was just synchronous, they added the callback on the 0.8. So, check the node.js version to be sure that the {cb} is correctly handled.