I'm facing this weird issue in NodeJS when using with Passport.js, Express and Mongoose. Basically, I get an error saying "Cannot set headers after they are sent to the client" even though I don't send more than one header.
I've read other posts and tried them out as well, and none of them worked.
I've dug through github issues and I can't seem to find a solution. I get the problem that this error is triggered when I send multiple response headers, but the fact is that I am not sending multiple headers. It seems just weird.
This is my stack trace:
(node:9236) DeprecationWarning: current URL string parser is deprecated, and will be removed in a future version. To use the new parser, pass option { useNewUrlParser: true } to MongoClient.connect.
Server Running on port 5000
MongoDB Connected Error
[ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the
client
at validateHeader (_http_outgoing.js:503:11)
at ServerResponse.setHeader (_http_outgoing.js:510:3)
at ServerResponse.header (/Users/lourdesroashan/code/github/devlog/node_modules/express/lib/response.js:767:10)
at ServerResponse.json (/Users/lourdesroashan/code/github/devlog/node_modules/express/lib/response.js:264:10)
at Profile.findOne.then.profile (/Users/lourdesroashan/code/github/devlog/routes/api/profile.js:27:30)
at <anonymous>
This is my server code:
router.get("/userprofile", passport.authenticate('jwt', { session: false }), (req, res) => {
Profile.findOne({ user: req.user.id }).then(profile => {
if (!profile) {
return res.status(404).json({ error: "No Profile Found" });
}
else {
res.json(profile);
}
}).catch(err => {
console.log(err);
})
});
I understand what the error means, but from what I know, I don't think I am sending multiple headers, I even checked by console.log that only one of the blocks is run.
Thank you so much in advance! :)
Full Code at: https://github.com/lourdesr/devlog
EDIT:
I figured it out. It was a problem in my passport.js while trying to get the authenticated user. I forgot to use 'return' on the 'done' method, which had caused it. Just added the return statement and it worked!
Saeed Awan :
Because of multiple response sending in your request. if you use return key word in your else condition your code will run properly\nif (!profile) {\n return res.status(404).json({ error: "No Profile Found" });\n}\nelse {\n **return** res.json(profile);\n}\n",
2020-12-14T07:11:54
Rajesh Khadka :
This also happen when you tries to send the multiple response for a same request !!\nSo make sure you always use return keyword to send response to client inorder to stop the further processing !!",
2022-04-14T17:53:14
Yash Jadhav :
Where you have this:\nif (!user) { errors.email = "User not found"; res.status(404).json({ errors }); }\nYou need to change it to:\nif (!user) { errors.email = "User not found"; return res.status(404).json({ errors }); }",
2022-07-04T12:20:13
user8758751 :
I got the same error using express and mongoose with HBS template engine. I went to Expressjs and read the docs for res.render, and it says // if a callback is specified, the rendered HTML string has to be sent explicitly. So I wasnt originally sending my html explicitly in the callback,. This is only for a contact form btw, not login info, albeit GET\n\n//Original\nlet { username, email } = req.query; //My get query data easier to read\n\nres.status(200).render('index', { username, email });\n\n\n\n//Solution without error. Second param sending data to views, Third param callback\n\nres.status(200).render('index', { username, email }, (err, html)=>{\n res.send(html);\n });\n",
2019-08-14T20:10:05
KingJoeffrey :
I had this error from an if statement not having an else block.\nif(someCondition) {\nawait () => { } \n\n}\n\nawait () => { } \n\n\nI changed the above to this below and solved my issue\nif(someCondition) {\nawait () => { } \n\n} else { \nawait () => { } \n}\n\n\n",
2022-04-09T20:19:22
jfriend00 :
That particular error occurs whenever your code attempts to send more than one response to the same request. There are a number of different coding mistakes that can lead to this:\n\nImproperly written asynchronous code that allows multiple branches to send a response.\nNot returning from the request handler to stop further code in the request handler from running after you've sent a response.\nCalling next() when you've already sent a response.\nImproper logic branching that allows multiple code paths to execute attempt to send a response.\n\nThe code you show in your question does not appear like it would cause that error, but I do see code in a different route here that would cause that error.\nWhere you have this:\nif (!user) {\n errors.email = "User not found";\n res.status(404).json({ errors });\n}\n\nYou need to change it to:\nif (!user) {\n errors.email = "User not found";\n res.status(404).json({ errors });\n // stop further execution in this callback\n return;\n}\n\nYou don't want the code to continue after you've done res.status(404).json({ errors }); because it will then try to send another response.\n\nIn addition, everywhere you have this:\nif (err) throw err;\n\ninside an async callback, you need to replace that with something that actually sends an error response such as:\nif (err) {\n console.log(err);\n res.sendStatus(500);\n return;\n}\n\nthrowing inside an async callback just goes back into the node.js event system and isn't thrown to anywhere that you can actually catch it. Further, it doesn't send a response to the http request. In otherwords, it doesn't really do what the server is supposed to do. So, do yourself a favor and never write that code in your server. When you get an error, send an error response.\n\nSince it looks like you may be new here, I wanted to compliment you on including a link to your full source code at https://github.com/lourdesr/devlog because it's only by looking at that that I was able to see this place where the error is occuring.",
2018-08-31T20:59:23
Page COW :
For me, I accidentally put a res.status inside of a for loop. So my server would trigger the error the second time a res.status was returned. I needed to put the res.status outside of the for loop so it would only trigger once within the function.",
2022-08-30T18:59:39
Chunky Chunk :
I was receiving this error because of a foolish mistake on my part. I need to be more careful when referencing my other working code. The truly embarrassing part is how long I spent trying to figure out the cause of the error. Ouf! \n\nBad:\n\nreturn res\n .send(C.Status.OK)\n .json({ item });\n\n\nGood:\n\nreturn res\n .status(C.Status.OK)\n .json({ item });\n",
2019-08-05T09:31:59
Reda El Ouahabi :
\nFirst of all : make sure you didn't miss any asynchronous action without an async/await or use promises/callbacks.\nThen attach any res with the return keyword : return res.status(..).json({});\nAnd finally which was my problem: don't use return res.sendStatus if you always have some return res... inside a callback function, but you can always do a retun res.status(); \nin my case it was : \nusers.save((err,savedDoc){ \nif(err) return res.status(501).json({}) \nres.status(200).json({}); \n}); \nreturn res.status(500); // instead ofdoing return res.sendStatus(500)\n",
2022-12-07T02:35:29
Mohammad Reza Mrg :
Use ctrl + F hotkey and find all 'res.' keywords\nthen replace them with 'return res.',\nchange all 'res.' to 'return res.'\n\nsomething like this:\nres.send() change to --> return res.send()\nmaybe you have 'res.' in some block, like if() statement",
2021-05-06T13:06:27
sina :
you have to enable Promises in your programm, in my case i enabled it in my mongoose schema by using mongoose.Promise = global.Promise .\nThis enables using native js promises.\n\nother alternatives to this soloution is :\n\nvar mongoose = require('mongoose');\n// set Promise provider to bluebird\nmongoose.Promise = require('bluebird');\n\n\nand\n\n// q\nmongoose.Promise = require('q').Promise;\n\n\nbut you need to install these packages first.",
2020-02-11T16:19:05
Ivan of uganda :
Sorry for the Late response, \nAs per the mongoose documentation \"Mongoose queries are not promises. They have a .then() function for co and async/await as a convenience. However, unlike promises, calling a query's .then() can execute the query multiple time\"\n\nso to use promises\n\nmongoose.Promise = global.Promise //To use the native js promises\n\n\nThen\n\nvar promise = Profile.findOne({ user: req.user.id }).exec()\npromise.then(function (profile){\n if (!profile) {\n throw new Error(\"User profile not found\") //reject promise with error\n }\n return res.status(200).json(profile) //return user profile \n}).catch(function (err){\n console.log(err); //User profile not found\n return res.status(404).json({ err.message }) //return your error msg\n})\n\n\nhere is an nice article about switching out callbacks with promises in Mongoose\n\nand this answer on mongooses promise rejection handling Mongoose right promise rejection handling",
2019-05-09T10:10:08
Christhopher Lion :
My problem besides not returning, i was forgetting to await an asynchronous function in the handler. So handler was returning and after a bit the async function did its thing. 🤦🏻♀️\nBefore:\nreq.session.set('x', {...});\nreq.session.save();\nreturn req.status(200).end();\n\nWhen i needed to await:\nreq.session.set('x', {...});\nawait req.session.save();\nreturn req.status(200).end();\n",
2021-10-13T11:42:26
Eugène Beliaev :
There is a simple fix for the node error [ERR_HTTP_HEADERS_SET]. You need to add a return statement in front of your responses to make sure your router exits correctly on error:\nrouter.post("/", async (req, res) => {\n \n let user = await User.findOne({email: req.body.email}); \n if (!user) **return** res.status(400).send("Wrong user");\n \n});\n",
2020-12-15T22:17:21
Bilal Amin :
In react, if your are calling the function in useEffect hook, make sure to add a dependency to the dependency Array.",
2022-02-02T08:37:51