I am using node express API in my application, I am facing below issue for API.
I have API which accept header parameter test and values like 1 to 5. Response is depends on header value, different response for different header parameter value.
Problem : If I am using with Single client (say POSTMAN) it is working fine, but if I am using two POSTMAN with different header parameter say in one window test=2 and
another window test=5 and if I send both request one after another then on both POSTMAN window I am getting response whichever I am sending first.
For response after some backend work I am sending response.
Below code I am using..
router.post('/:sample/:temp', function(req, res){
....
if(obj.st == "acknowledged"){
res.write(message);
}else if (obj.st == "completed") {
res.write(message);
res.end();
}
}
Update 1 :
After getting request I am waiting for response from MQTT topic where first I am getting acknowledged which I am storing like res.write(message) and after some time (may be after 1 second) on same topic I am getting completed after that I am sending response to user(API response).
router.post('/:sample/:temp', function(req, res){
....
client.on('message', function(topic, message){
var obj = JSON.parse(message);
if(obj.st == "acknowledged"){
res.write(message);
res.write("\n\n");
}else if (obj.st == "completed") {
res.write(message);
res.end();
client.end();
}
});
}
Update 2 :
Using below URL for POST request
http://localhost:8080/myapp/<path_param1>/<path_param2>
Related
I am trying to make a Google Home app and I am using webhooks with express.js running on a local server as fulfilment. I would like to use the "request.body.originalDetectIntentRequest.payload.user.userStorage" parameter from the request to identify a user when the webhook sends a post request to my server. The userId given with this request is equal to a log-filename that I store locally for each user where I keep track of different things per user.
I got the idea of handling things like this from an earlier post here on stack overflow. In the answer given by Prisoner, he talks about the importance of the response that you have to send back. So far so good, I tried to implement this in my code by sending a response once the new userId is made but I keep getting the same error :
(node:21236) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:518:11)
So it probably has to do with the fact that I have a line agent.handleRequest(intentMap); at the end of my code which will handle the request and send a response back to the user itself.
How do I solve this? I already tried to find a solution for this problem but the after trying different things, there is only one thing I can think of which would be to expand the response before sending it with the payload.google.userStorage variable even though I have tried response.write but that was giving me the same error.
My code:
app.post('/', express.json(), (request, response) => {
const agent = new WebhookClient({ request, response });
console.log('Dialogflow Request headers: ' + JSON.stringify(request.headers));
console.log('Dialogflow Request body: ' + JSON.stringify(request.body));
let userStorage = request.body.originalDetectIntentRequest.payload.user.userStorage || JSON.stringify({});
let userId;
console.log("userStorage", userStorage);
userStorage = JSON.parse(userStorage);
console.log("userStorage_after_parsing", userStorage);
if (userStorage.hasOwnProperty('userId')) {
userId = userStorage.userId;
console.log('user was already defined:' + userId);
} else {
let uuid = require('uuid/v4');
checkNewUser = true;
userId = uuid();
userStorage.userId = userId
console.log(userId);
response.send({
'payload': {
'google': {
'userStorage': JSON.stringify(userStorage)
}
}
}
);
//rest of the code
agent.handle(intentMap)
UPDATED QUESTION:
After prisoner's answer, I decided to include the code of the handleWelcome intent where I would like to paste the code into to extend the response with the the userStorage variable:
function handleWelcome(agent) {
//code to add userStorage to the response?
if (checkIfUserVerified() === true) {
agent.add('Hi.');
//updateLog('User just said hi.');
let userObj = readJsonSync(userId + '.json');
userObj.logs.push('User just started talking to this chatbot ' + getCurrentDateTime());
fs.writeFileSync(userId + '.json', JSON.stringify(userObj));
}
else {
close('Please make sure you are a verified user before using this version of SMART4MD. To do so, read the SMART4MD Voice assistant manual.');
agent.setFollowupEvent('GOODBYE');
}
}
Note the comment in the answer you cite where it says
// Make sure you include the userStorage as part of the response
"part of" the response - not the response itself. In your code, you're sending back the JSON to sent the user storage before your Intent Handler is called. Once something is sent, the connection is closed, so nothing further can be sent - including the reply you want. Which is why you get the error.
You don't show any of your Intent Handler functions, so it is difficult to give you an exact answer, but the general solution would be to set the userid in userStorage as part of a function that each handler calls.
I am developing an API which takes input in XML containing IDs for media and gives output in XMLform with details of given IDs. I am facing a problem while sending the response of second simultaneous request; here the second request goes into loop showing "loading" on postman.
What I am doing is calling a function in app.post which parses the media and gives output in the callback and send it using res.send, but it works only for single request.
While doing parallel request to same API either it goes in loop or it gives can't set the headers after they are sent as I am using res.send but res.send is the only way which I can use to send the response (even the next doesn't work).
var getCompositeData = function(req, res, next){
abc.getData(req.body, function(err, xmlOutput){
if(err){
console.log("error");
} else {
xmlData = xmlOutput
return next()
}
}
app.post(apiUrl, [
rawBodyParser({
type: 'application/xml'
}),
app.oauth.authorise()
], getCompositeData, function (req, res) {
res.setHeader('Content-Type', 'application/xml');
res.send(xmlData);
});
There are several issues with your code:
if (err) {
console.log("error");
}
If an error occurs, you still need to make sure a response will be sent back, otherwise the request will stall until a timeout happens. You can pass an error to next, and Express will handle it:
if (err) {
return next(err);
}
Next problem:
xmlData = xmlOutput
xmlData is an undeclared variable, which gets overwritten with each request. If two requests happens at (almost) the same time, it's likely that one client gets back an incorrect response (remember, Node.js runs JS code in a single thread; there is not thread-local storage so xmlData gets shared between all requests).
A good place to "store" this sort of data is in res.locals:
res.locals.xmlData = xmlOutput;
return next();
// and later:
res.send(res.locals.xmlData);
I have 2 clients and one node.js server url - localhost:8888/ServerRequest. The First client GETs from this url and waits for 20 seconds to see if the Second client has POSTed some data for the first client within the 20 second timeout period or not.If the second client did POST before the timeout, then that value is returned to the GET request, else a default value is returned for the GET request. I am not sure what is the best way to implement this. I am trying something like this, but it is not working as desired -
function ServerRequest(response, postData , request)
{
var id;
if(request.method == "GET")
{
id= setTimeout(function( )
{
// handle timeout here
console.log("Got a timeout, sending default value");
cmd = "DefaultVal";
response.write("<?xml version=\"1.0\" encoding=\"UTF-8\"?><list id=\"20101001\"><com type=\"" + cmd + "\"></com></list>")
response.end()
},20000);
}
else if(request.method == "POST")
{
console.log("Received POST, sending POSTed value");
cmd = postData;
//Cancel Timeout
clearTimeout(id);
console.log(" \n Received POST")
response.write("<?xml version=\"1.0\" encoding=\"UTF-8\"?><list id=\"20101001\"><com type=\"" + cmd + "\"></com></list>")
response.end()
}
}
Another approach in my mind was to use 2 separate URLs - One for GET Request (/ServerRequest) and the other for POST Request (/PostData). But then how will I pass the POSTed data from one URL to the other if received before the timeout?
EDIT: I think I know now what I exactly need. I need to implement a longpoll, where a client sends a GET request, and waits for a timeout period (the data might not be immediately available to consume, so it waits for 20 seconds for some other client to POST some data for the first client to consume). In case timeout occurs, a default value is returned in response to the GET request from the first client. I'm working on the longpoll implementation I found here, I'll update if I am able to succeed in what I'm trying. If someone can point me or provide me with a better example, it will be helpful.
Edit: removed my original code after a more careful reading of the question.
The best solution would probably be websockets the browser will appear to hang waiting for 20 seconds.
Using a library like socket.io you can do this
var io = require('socket.io').listen(8888);
function postHandler(req, data, res){
io.sockets.emit("response" , data)
}
then client side
<script src="/socket.io/socket.io.js"></script>
<script>
var socket = io.connect('http://localhost:8888');
socket.on('response', function (data) {
console.log(data);
});
</script>
I have a server in node.js which handles registration from users.
When someone attempts to register I first check if the introduced email already exists in my database, and if not I send a response back saying that that email has already been used.
The problem is that when I send a response with response.write() when the browser receives the response it replaces all the webpage by the response text, and what I want is to use that response to display a message next to the form in the registration page.
I also want to get the response with a Dart event listener so that the client knows that the email is in use and can display the message. My code for making the HTTP request with Dart is the following:
signupSubmit.onClick.listen((e) {
var req = new HttpRequest();
req.onReadyStateChange.listen((e) {
if (req.readyState == HttpRequest.DONE) {
print('Data submitted!');
}
});
req.open('POST', signupForm.action);
req.send(JSON.encode(serializeForm(signupForm)));
});
serializeForm(FormElement form) {
var data = {};
form.querySelectorAll('input,select').forEach((Element el) {
if (el is InputElement)
data[el.name] = el.value;
});
return data;
}
So how can I send a response that I can process in the client?
And how can I get the server response with Dart?
The signupSubmit click seems to submit its <form>. You can block the default form submission with :
signupForm.onSubmit.listen((e) => e.preventDefault());
I'm really new to node.js so please bear with me if I'm making a obvious mistake.
To understand node.js, i'm trying to create a webserver that basically:
1) update the page with appending "hello world" everytime the root url (localhost:8000/) is hit.
2) user can go to another url (localhost:8000/getChatData) and it will display all the data built up from the url (localhost:8000/) being triggered
Problem I'm experiencing:
1) I'm having issue with displaying that data on the rendered page. I have a timer that should call get_data() ever second and update the screen with the data variable that stores the appended output. Specifically this line below response.simpleText(200, data); isn't working correctly.
The file
// Load the node-router library by creationix
var server = require('C:\\Personal\\ChatPrototype\\node\\node-router').getServer();
var data = null;
// Configure our HTTP server to respond with Hello World the root request
server.get("/", function (request, response) {
if(data != null)
{
data = data + "hello world\n";
}
else
{
data = "hellow world\n";
}
response.writeHead(200, {'Content-Type': 'text/plain'});
console.log(data);
response.simpleText(200, data);
response.end();
});
// Configure our HTTP server to respond with Hello World the root request
server.get("/getChatData", function (request, response) {
setInterval( function() { get_data(response); }, 1000 );
});
function get_data(response)
{
if(data != null)
{
response.writeHead(200, {'Content-Type': 'text/plain'});
response.simpleText(200, data);
console.log("data:" + data);
response.end();
}
else
{
console.log("no data");
}
}
// Listen on port 8080 on localhost
server.listen(8000, "localhost");
If there is a better way to do this, please let me know. The goal is to basically have a way for a server to call a url to update a variable and have another html page to report/display the updated data dynamically every second.
Thanks,
D
The client server model works by a client sending a request to the server and the server in return sends a response. The server can not send a response to the client that the client hasn't asked for. The client initiates the request. Therefore you cannot have the server changing the response object on an interval.
The client will not get these changes to the requests. How something like this is usually handled as through AJAX the initial response from the server sends Javascript code to the client that initiates requests to the server on an interval.
setTimeout accepts function without parameter which is obvious as it will be executed later in time. All values you need in that function should be available at the point of time. In you case, the response object that you are trying to pass, is a local instance which has scope only inside the server.get's callback (where you set the setTimeout).
There are several ways you can resolve this issue. you can keep a copy of the response instance in the outer scope where get_data belongs or you can move the get_data entirely inside and remove setTimeout. The first solution is not recommended as if getChatData is called several times in 1sec the last copy will be prevailing.
But my suggestion would be to keep the data in database and show it once getChatData is called.