Am using a function to save data. Using the http.request option. It is working fine. If I call the same function in a loop, some of the data not saving in database. Also getting the parse error message for some response.
How Can I call the function of http.request in a loop?
for (var i = 1; i <= 23; i++) {
turn_timer(i);
}
function turn_timer(nos) {
try {
var str = "num=" + nos;
var len = str.length;
win_settings.headers = {
'Content-length': len,
'Content-Type': 'application/x-www-form-urlencoded'
}
var request = http.request(win_settings, function(response) {
response.on('data', function(data) {
});
response.on('error', function(err) {
});
response.on('end', function() {
});
});
request.on('error', function(err) {
});
request.write(str + "\0");
request.end();
} catch (err) {
console.log(err);
}
}
Check the scope of your variable that stores message because async function call may overwrite it.
I believe your problem is because you are using a for loop, instead of going with a more asynchronous approach. Here is a quick attempt to solve your problem. I have omitted some of your code, as it seemed to be incomplete. I have left the important parts and added a few things based on an answer to a similar question.
var http = require('http'),
async = require('async');
function turn_timer(n, callback) {
var var str = "num=" + n,
len = str.length,
req;
win_settings.headers = {
'Content-length': len,
'Content-Type': 'application/x-www-form-urlencoded'
};
req = http.request(options, function(response) {
...
callback(null);
});
req.on('error', function(err) {
...
callback(err);
});
req.end();
}
async.timesSeries(23, function (n, next) {
turn_timer(options, function(err) {
next(err);
});
});
For more information, you can read more about async.timesSeries here: https://github.com/caolan/async#timesseriesn-callback
Related
I have the code below, and it seems to call the var promiseFeedback is called and I don't know why... This means it is called even when an error occurs when I create document. Whereas is should only be called if there is no err in the createDocument.
Is anyone able to clear up why?
if (json) {
createDocument(documentUrl, context, json, function(res){
var promiseFeedback = callFB (context, res);
var collection = `mydb`
client.createDocument(collection, res, (err, result) => {
if(err) {
context.log(err);
return context.done();
} else {
Promise.all([promiseFeedback]).then(function(results){
context.log("promiseFeedback: " + results[0]);
context.done();
});
}
});
});
}
function callFB(context, res) {
return new Promise((resolve, reject) => {
var requestUrl = url.parse( URL );
var requestBody = {
"id": res.id
};
var body = JSON.stringify( requestBody );
const requestOptions = {
hostname: requestUrl.hostname,
path: requestUrl.path,
method: 'POST',
headers: {
'Content-Type': 'application/json',
'Content-Length': Buffer.byteLength(body),
}
};
var request = https.request(requestOptions, function(res) {
var data ="";
res.on('data', function (chunk) {
data += chunk
});
res.on('end', function () {
resolve(true);
})
}).on('error', function(error) {
context.log("request error:", error);
resolve(false);
});
request.write(body);
request.end();
});
}
var promiseFeedback = callFB (context, res);
This statement executes callFB immediately, not just assigns another name to the promise. This promise callFB is out of the callback(scope) of err and Promise.all([promiseFeedback]), it runs no matter what the result of client.createDocument is.
To fix this:
Remove var promiseFeedback = callFB (context, res); and change Promise.all([promiseFeedback]) to callFB(context, res). You don't need to use Promise.all as you only have one promise to resolve.
Or you can just move var promiseFeedback = callFB (context, res); into else segment.
I use NodeJS and request lib to make some request to an API.
I understand now that all requests are async and so it doesn't "wait" the result of the GET call, so the index of my Loop is always the same.
I was wondering if there was any simple way (without any lib) to wait for the response of the request call ?
For now, my code is this :
for (var i in entries) {
var entryId = entries[i]['id'];
var options = {
url: 'https://api.com/'+ entryId +'/get/status',
method: 'GET',
headers: {
'Authorization': auth
}
};
console.log(' ENTRY ID > '+ entryId);
request(options, function(error, response, body) {
var response = JSON.parse(body);
if (response.status.code == 200) {
var id = response.status.id;
var data = [];
data['id'] = id;
data = JSON.stringify(data);
// show first entryId of loop
console.log(' > MY ID : '+ id + ' - '+ entryId);
options = {
host: hostname,
port: 80,
path: '/path/function2',
method: 'PUT'
};
var post = http.request(options, function(json) {
var body = '';
json.on('data', function(d) {
body += d;
});
json.on('end', function() {
console.log('> DONE');
});
}).on('error', function(e) {
console.log(e);
});
post.write(data);
post.end();
}
});
}
You are looking for async/await.
Wrap your logic inside an async function, then you can await for the promise to resolve.
const request = require('request-promise')
async function foo (a) {
for (i in a)
try {
let a = await request('localhost:8080/')
// a contains your response data.
} catch (e) {
console.error(e)
}
}
foo([/*data*/])
Just use the promisified version of request module.
You also can use Promises to wait for your async code to finish.
function asyncCode(msg, cb){
setTimeout(function() {cb(msg);}, 1000);
}
var p1 = new Promises(function(resolve){
asyncCode("my asyncCode is running", resolve);
});
p1.then(function(msg) {
console.log(msg);
}).then(function() {
console.log("Hey I'm next");
});
console.log("SyncCode, Async code are waiting until I'm finished");
how to use Q to make it wait until previous response has come from the server.
What I am looking to do here is compare the response from test server and production server for the same request.
I get the responses back from both the servers, but unable to compare them since the assert statement is executed before the response comes back.
Any one know what I am doing wrong. heres the code.
var Q = require('q');
var path='';
var prodResponse = '';
var tstReponse = '';
Q.fcall(readFile())
.then(secondFunction())
.then(thirdFunction())
.then(function(){
console.log("prodResponse: "+prodResponse);
console.log("tstResponse: "+tstResponse);
assert.strictEqual(prodResponse, tstResponse)
})
.catch(function(){
console.log('error occurred');
})
.done();
function readFile(){
fs.readFile('hostname.json', function (err, data) {
if (err) return console.error(err);
path = JSON.parse(data);
return JSON.parse(data);
});
}
function secondFunction(){
var prodOptions = {
hostname: 'somehostname.com',
port: 80,
path: "/path?"+path.path,
method: 'POST',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
auth : ''
};
return http.request(prodOptions, function(res) {
console.log('Prod');
res.setEncoding('utf8');
res.on('data', function (chunk) {
prodResponse = chunk;
return chunk;
});
res.on('end', function() {
console.log('No more data in response.');
})
}).on('error', function(e) {
console.log('problem with request: ' + e.message);
}).end();
}
function thirdFunction(){
// same a second, only difference is the response http.
}
There is multiple errors in your code
Q.fcall(readFile())
Your q variable is q and not Q. So this line will crash because Q is undefined (javascript is case sensitive).
Then, readFile doesn't return any promise (in fact, it returns nothing). So the q library can't use anything to wait the end of any asynchronous work. The then callbacks will be fired immediatly.
You can use Q.ninvoke to make your readFile function return a promise, and you can use Q.defer to create and return a promise from your secondFunction:
var Q = require('q');
var path='';
var prodResponse = [];
var tstReponse = '';
readFile()
.then(secondFunction())
.then(thirdFunction())
.then(function(){
console.log("prodResponse: "+prodResponse);
console.log("tstResponse: "+tstResponse);
assert.strictEqual(prodResponse, tstResponse)
})
.catch(function(){
console.log('error occurred');
})
.done();
function readFile(){
return Q.ninvoke(fs, 'readFile', 'hostname.json').then(function (data) {
path = JSON.parse(data);
return path;
}, function (err) {
console.error(err);
});
}
function secondFunction(){
var prodOptions = {
hostname: 'somehostname.com',
port: 80,
path: "/path?"+path.path,
method: 'POST',
headers: {
'Content-Type': 'application/json;charset=UTF-8'
},
auth : ''
};
var defer = Q.defer();
var chunks = [];
http.request(prodOptions, function(res) {
console.log('Prod');
res.setEncoding('utf8');
res.on('data', function (chunk) {
chunks.push(chunk);
});
res.on('end', function() {
console.log('No more data in response.');
prodResponse = chunks.join('');
defer.resolve(prodResponse);
})
}).on('error', function(e) {
console.log('problem with request: ' + e.message);
defer.reject(e);
}).end();
return defer.promise;
}
function thirdFunction(){
// same a second, only difference is the response http.
}
I'm pretty new at node, so I may be going about this all wrong (if I am, don't be afraid to say) - I'd like to be able to create an object made of data from several different rest servers and return the final object to my calling function. For each rest api I have a function that looks a bit like this:
jobs.js
exports.get_users_jobs = function(options, onResult) {
var user = options.params.user;
console.log("Get jobs for user: " + user);
var optionsget = {
host: config.jobs_rest_host,
port: config.jobs_rest_port,
path: "/jobs3/user/" + user,
method: "GET",
headers: {
'Content-Type': 'application/json'
}
};
var reqGet = http.request(optionsget, function(res) {
var output = '';
res.setEncoding('utf-8');
res.on('data', function(chunk) {
output += chunk;
});
res.on('end', function() {
var obj = JSON.parse(output);
onResult.send(res.statusCode, obj);
});
});
reqGet.end();
reqGet.on('error', function(e) {
console.error('error: ' + e.message);
});
};
That works fine when I'm calling it directly from the browser, but now I'd like to call get_users_jobs from another function, take the data and plonk that into my uber object. So I've created something a bit like this (I've only put jobs in there for now, but soon there will be other variables)
users.js
var jobs = require('./jobs.js');
function User (jobs) {
this.jobs = jobs;
}
User.prototype.jobs = null;
/* lots of stuff that I don't think matters */
jobs_data = jobs.get_cb_users_jobs(req, res);
var u = User(jobs_data);
/* do lots of stuff with u like prepare reports etc */
But all that happens here is my jobs data is output in the browser (which makes sense since I have onResult.send(blah) - how can I construct my get_users_jobs function to just return the data from the rest call?
Thanks in advance to anyone that can help!
Instead of passing a response to your get_users_jobs, pass it a callback as a second parameter, something like this:
exports.get_users_jobs = function(options, cb) {
//...
//no changes
//...
var reqGet = http.request(optionsget, function(res) {
var output = '';
res.setEncoding('utf-8');
res.on('data', function(chunk) {
output += chunk;
});
res.on('end', function() {
var obj = JSON.parse(output);
cb(null, {
status: res.statusCode,
data: output
});
});
});
reqGet.end();
reqGet.on('error', function(e) {
cb(err);
});
};
and then in users.js:
jobs.get_cb_users_jobs(req, function(err, result) {
if (err) {
//handle the error
} else {
//do whatever you want with the result
}
});
Notice the call to callback inside res.on('data', ...) and res.on('error', ...) - this is a typical node.js callback pattern. You did the same thing, but passed the control to response instead of your own function.
If you still need to pass the result directly to response, add a wrapper function that passes
function(err, response) {
if (err) {
console.error('error: ' + e.message);
} else {
onResult.send(res.statusCode, obj);
}
}
as callback parameter to get_users_jobs
I need to iterate on an array, for each item I apply an operation by calling an HTTP call.
The difficulty is that i need to syncronize this process in order to call a callback after the loop (containing the array after all the operation executed by the HTTP call).
Let's consider this short example:
function customName(name, callback) {
var option = {
host:'changename.com',
path: '/'+name,
headers: { 'Content-Type': 'application/json' },
port: 80,
method:'POST'
};
var req = http.request(option, function(res) {
var output = "";
res.on('data', function (chunk) {
output += chunk;
});
res.on('end', function() {
var obj = JSON.parse(output);
callback(obj.res);
});
});
req.on('error', function(e) {
console.error(e.message);
});
req.end();
}
function changeNames(OldNames, callback) {
var Res = [];
for (name in OldNames) {
customName(OldNames[name], function(new_name) { Res.push(new_name); });
});
callback(Res);
}
var Names = ['toto', 'tata', 'titi'];
changeNames(Names, function(Names) {
//...
});
Here the loop is over before the first HTTP call, so the Res array is empty.
How can we synchronize this execution?
I know it's not very good to synchronize treatments in nodejs. Do you think it would be better to communicate the names one by one with the client and not building an array?
You can use async.map for that. You pass it your list of names, it will run the getOriginalName function (which you mistakenly called customName, I think) for each name and gather the result, and in the end it will call a function with an array of results:
var http = require('http');
var async = require('async');
function getOriginalName(name, callback) {
var option = {
host:'changename.com',
path: '/'+name,
headers: { 'Content-Type': 'application/json' },
port: 80,
method:'POST'
};
var req = http.request(option, function(res) {
var output = "";
res.on('data', function (chunk) {
output += chunk;
});
res.on('end', function() {
var obj = JSON.parse(output);
callback(null, obj.res);
});
});
req.on('error', function(e) {
callback(e);
});
req.end();
}
function changeNames(OldNames, callback) {
async.map(OldNames, getOriginalName, callback);
}
var Names = ['toto', 'tata', 'titi'];
changeNames(Names, function(err, NewNames) {
console.log('N', NewNames);
});