I'm doing a simple request with express & the request module and piping its response to res:
var pipe = request.get({
url: 'url-to-file'
});
pipe.on('response', function (response) {
req.on('close', function () {
// these methods won't work:
// pipe.unpipe();
// pipe.end();
// pipe.finish();
// pipe.close();
});
pipe.on('end', function () {
// this will never fire if I cancel the request
});
res.writeHead(response.statusCode, response.headers);
pipe.pipe(res);
});
This works like a charm, except if I cancel downloads. The end event won't fire and some seconds later, an ESOCKETTIMEDOUT error gets thrown.
How can I close the pipe? These node docs claim that I can call .unpipe, but all node gives is pipe.unpipe is not a funtion (tested with v0.12.7 & 4.2.2 & & 5.0.0), probably because it's not an original node stream.
I also tried using events like end, finish and close, but neither of them work.
request.get() does not return a pure node.js stream but rather a Request object which inherits from the native Stream class and adds some custom methods. The method you are looking for is Request#abort() (Source link).
Your code example would look like the following:
var pipe = request.get({
url: 'url-to-file'
});
pipe.on('response', function (response) {
req.on('close', function () {
pipe.abort();
});
pipe.on('end', function () {
// this will never fire if I cancel the request
});
res.writeHead(response.statusCode, response.headers);
pipe.pipe(res);
});
Related
On firebase function I need to get data from Paypal and do 4 things :
1. returns an empty HTTP 200 to them.
2. send the complete message back to PayPal using `HTTPS POST`.
3. get back "VERIFIED" message from Paypal.
4. *** write something to my Firebase database only here.
What I do now works but i am having a problem with (4).
exports.contentServer = functions.https.onRequest((request, response) => {
....
let options = {
method: 'POST',
uri: "https://ipnpb.sandbox.paypal.com/cgi-bin/webscr",
body: verificationBody
};
// ** say 200 to paypal
response.status(200).end();
// ** send POST to paypal back using npm request-promise
return rp(options).then(body => {
if (body === "VERIFIED") {
//*** problem is here!
return admin.firestore().collection('Users').add({request.body}).then(writeResult => {return console.log("Request completed");});
}
return console.log("Request completed");
})
.catch(error => {
return console.log(error);
})
As you can see when I get final VERIFIED from Paypal I try to write to the db with admin.firestore().collection('Users')..
I get a warning on compile :
Avoid nesting promises
for the write line.
How and where should I put this write at that stage of the promise ?
I understand that this HTTPS Cloud Function is called from Paypal.
By doing response.status(200).end(); at the beginning of your HTTP Cloud Function you are terminating it, as explained in the doc:
Important: Make sure that all HTTP functions terminate properly. By
terminating functions correctly, you can avoid excessive charges from
functions that run for too long. Terminate HTTP functions with
res.redirect(), res.send(), or res.end().
This means that in most cases the rest of the code will not be executed at all or the function will be terminated in the middle of the asynchronous work (i.e. the rp() or the add() methods)
You should send the response to the caller only when all the asynchronous work is finished. The following should work:
exports.contentServer = functions.https.onRequest((request, response) => {
let options = {
method: 'POST',
uri: "https://ipnpb.sandbox.paypal.com/cgi-bin/webscr",
body: verificationBody
};
// ** send POST to paypal back using npm request-promise
return rp(options)
.then(body => {
if (body === "VERIFIED") {
//*** problem is here!
return admin.firestore().collection('Users').add({ body: request.body });
} else {
console.log("Body is not verified");
throw new Error("Body is not verified");
}
})
.then(docReference => {
console.log("Request completed");
response.send({ result: 'ok' }); //Or any other object, or empty
})
.catch(error => {
console.log(error);
response.status(500).send(error);
});
});
I would suggest you watch the official Video Series on Cloud Functions from Doug Stevenson (https://firebase.google.com/docs/functions/video-series/) and in particular the first video on Promises titled "Learn JavaScript Promises (Pt.1) with HTTP Triggers in Cloud Functions".
I would like to test my simple API that has /groups URL.
I want to make an API request to that URL (using Axios) before all tests begin and make the response visible to all test functions.
I am trying to make the response visible but not able to make it work. I followed a similar case with filling out the DB upfront but no luck with my case.
My simple test file below:
var expect = require('chai').expect
var axios = require('axios')
var response = {};
describe('Categories', function() {
describe('Groups', function() {
before(function() {
axios.get(config.hostname + '/groups').then(function (response) {
return response;
})
});
it('returns a not empty set of results', function(done) {
expect(response).to.have.length.greaterThan(0);
done();
})
});
});
I tried also a sligh modification of before function:
before(function(done) {
axios.get(config.hostname + '/groups')
.then(function (response) {
return response;
}).then(function() {
done();
})
});
but no luck too.
The error I am getting is simply that response isn't changing nor is visible within it. AssertionError: expected {} to have property 'length'
Summarising: How can I pass response from axios inside to in()?
Your first form is incorrect, because you're not returning the chained promise. As such, mocha has no way of knowing when your before is finished, or even that it's async at all. Your second form will solve this problem, but since axios.get already returns a promise, it's kind of a waste not to use mocha's built-in promise support.
As for making the response visible in the it, you need to assign it to a variable in a scope that will be visible within the it.
var expect = require('chai').expect
var axios = require('axios')
var response;
describe('Categories', function() {
describe('Groups', function() {
before(function() {
// Note that I'm returning the chained promise here, as discussed.
return axios.get(config.hostname + '/groups').then(function (res) {
// Here's the assignment you need.
response = res;
})
});
// This test does not need the `done` because it is not asynchronous.
// It will not run until the promise returned in `before` resolves.
it('returns a not empty set of results', function() {
expect(response).to.have.length.greaterThan(0);
})
});
});
I'm looking for a solution to waiting for an event to happen before sending a HTTP response.
Use Case
The idea is I call a function in one of my routes: zwave.connect("/dev/ttyACM5"); This function return immediately.
But there exists 2 events that notice about if it succeed or fail to connect the device:
zwave.on('driver ready', function(){...});
zwave.on('driver failed', function(){...});
In my route, I would like to know if the device succeed or fail to connect before sending the HTTP response.
My "solution"
When an event happen, I save the event in a database:
zwave.on('driver ready', function(){
//In the database, save the fact the event happened, here it's event "CONNECTED"
});
In my route, execute the connect function and wait for the event to
appear in the database:
router.get('/', function(request, response, next) {
zwave.connect("/dev/ttyACM5");
waitForEvent("CONNECTED", 5, null, function(){
response.redirect(/connected);
});
});
// The function use to wait for the event
waitForEvent: function(eventType, nbCallMax, nbCall, callback){
if(nbCall == null) nbCall = 1;
if(nbCallMax == null) nbCallMax = 1;
// Looking for event to happen (return true if event happened, false otherwise
event = findEventInDataBase(eventType);
if(event){
waitForEvent(eventType, nbCallMax, nbCall, callback);
}else{
setTimeout(waitForEvent(eventType, callback, nbCallMax, (nbCall+1)), 1500);
}
}
I don't think it is a good practice because it iterates calls over the database.
So what are your opinions/suggestions about it?
I've gone ahead and added the asynchronous and control-flow tags to your question because at the core of it, that is what you're asking about. (As an aside, if you're not using ES6 you should be able to translate the code below back to ES5.)
TL;DR
There are a lot of ways to handle async control flow in JavaScript (see also: What is the best control flow module for node.js?). You are looking for a structured way to handle it—likely Promises or the Reactive Extensions for JavaScript (a.k.a RxJS).
Example using a Promise
From MDN:
The Promise object is used for asynchronous computations. A Promise represents a value which may be available now, or in the future, or never.
The async computation in your case is the computation of a boolean value describing the success or failure to connect to the device. To do so, you can wrap the call to connect in a Promise object like so:
const p = new Promise((resolve) => {
// This assumes that the events are mutually exclusive
zwave.connect('/dev/ttyACM5');
zwave.on('driver ready', () => resolve(true));
zwave.on('driver failed', () => resolve(false));
});
Once you have a Promise representing the state of the connection, you can attach functions to its "future" value:
// Inside your route file
const p = /* ... */;
router.get('/', function(request, response, next) {
p.then(successful => {
if (successful) {
response.redirect('/connected');
}
else {
response.redirect('/failure');
}
});
});
You can learn more about Promises on MDN, or by reading one of many other resources on the topic (e.g. You're Missing the Point of Promises).
Have you tried this? From the look of it, your zwave probably have already implemented an EventEmmiter, you just need to attach a listener to it
router.get('/', function(request, response, next) {
zwave.connect("/dev/ttyACM5");
zwave.once('driver ready', function(){
response.redirect(/connected);
});
});
There is a npm sync module also. which is used for synchronize the process of executing the query.
When you want to run parallel queries in synchronous way then node restrict to do that because it never wait for response. and sync module is much perfect for that kind of solution.
Sample code
/*require sync module*/
var Sync = require('sync');
app.get('/',function(req,res,next){
story.find().exec(function(err,data){
var sync_function_data = find_user.sync(null, {name: "sanjeev"});
res.send({story:data,user:sync_function_data});
});
});
/*****sync function defined here *******/
function find_user(req_json, callback) {
process.nextTick(function () {
users.find(req_json,function (err,data)
{
if (!err) {
callback(null, data);
} else {
callback(null, err);
}
});
});
}
reference link: https://www.npmjs.com/package/sync
I'm using AWS Lambda to drive an Alexa Skill Kit development. In an attempt to track events, I'd like the script to send an HTTP request on launch, however from the cloud logs it appears as though the http.get function is being skipped during the execution process.
The code is shown below (google.com replaces the analytics tracking url - which has been tested in the browser);
exports.handler = function (event, context) {
var skill = new WiseGuySkill();
var http = require('http');
var url = 'http://www.google.com';
console.log('start request to ' + url)
http.get(url, function(res) {
console.log("Got response: " + res.statusCode);
// context.succeed();
}).on('error', function(e) {
console.log("Got error: " + e.message);
// context.done(null, 'FAILURE');
});
console.log('end request to ' + url);
skill.execute(event, context);
};
The context objects have been commented out to allow for 'skill.execute' to function, yet either way this HTTP request is not executing. Only the 'start' and 'end' console.logs are recorded, those internal in the function do not.
Is this a async issue? Thanks.
You need to make sure the handler is being triggered. There are two ways of accomplishing this:
You could set up a new API endpoint and execute a request on that.
You could hit the Test button and your function would be invoked with the given data.
I copied and pasted your whole snippet except for the first and the last lines (because I don't have customSkill defined anywhere). I was able to get a 200 response code.
In order to successfully complete the http request, the http.get function must be incorporated into a callback function. Else the process will not be completed and will end prematurely, using a callback allows the http request to complete (with or without an error) before continuing with the rest of the function.
WiseGuySkill.prototype.eventHandlers.onLaunch = function (launchRequest, session, response) {
// Call requestFunction to make the http.get call.
// Get response from requestFunction using requestCallback
requestFunction(function requestCallback(err) {
// If error occurs during http.get request - respond with console.log
if (err) {
console.log('HTTP Error: request not sent');
}
ContinueIntent(session,response);
});
};
The function 'requestFunction' calls http.get and fires the callback.
function requestFunction(requestCallback){
var url = "http://www.google.com";
http.get(url, function(res) {
console.log("Got response: " + res.statusCode);
requestCallback(null);
}).on('error', function (e) {
console.log("Got error: ", e);
});
}
And obviously ensure you have required 'http' at the start of the script.
Hope this helps anybody else new to this!
I try to put many callbacks in a callback, but the program will shut down after the return of several success requests and post "socket hang up" error. I try to collect data from response and output them at once, can someone tell me which part goes wrong...
By the way, I hide the details of request method, I promise the request method works on http call.
http.request(options1,function(data){
var condition=data.length;
var result=[];
data.foreach(item,function(data){
http.request(options2, function(data){
if(data) result.push(data);
condition--;
if(condition<=0) console.log(result);
}
});
});
for my http.request method
var request=function(options,callback){
http.request(options,function(res){
var body;
res.on('data',function(chunk){
body+=chunk;
});
res.on('end',function(){
callback(JSON.parse(body));
});
request.end();
};
That's not the correct usage of http.request().
The http.request() callback is passed an IncomingMessage object, not buffered response data.
EDIT: Your custom request() should look something like this, although you should handle errors too. Note the proper placement of request.end() and initializing var body = '':
function request(options, callback) {
http.request(options,function(res) {
var body = '';
res.setEncoding('utf8');
res.on('data',function(chunk) {
body += chunk;
}).on('end',function() {
callback(JSON.parse(body));
});
}).end();
}
You're missing .end() for your requests so that node.js knows you are ready to actually send the HTTP request: http.request(..., ....).end();. This is the cause of your particular error... the server hangs up the connection because it got tired of waiting for your request after the TCP connection was opened.