Error: Can't set headers after they are sent

[joncursi]

Every time I make a graphql query from my client, the server console outputs:

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 32): Error: Can't set headers after they are sent.

The data arrives fine on the client, but I keep getting this error spit out on the server console. It only happens on graphql queries (I'm using Apollo client and Apollo server). I'm not sure where to start since there is no stack trace, so I figured I would start here and see if anyone has any ideas on what's going on!

    "graphql": "0.10.5",
    "graphql-date": "^1.0.3",
    "graphql-loader": "^1.2.1",
    "graphql-log": "^0.1.3",
    "graphql-redis-subscriptions": "^1.2.0",
    "graphql-server-express": "^1.0.2",
    "graphql-subscriptions": "^0.4.4",
    "graphql-tools": "^1.0.0",
    "graphql-type-json": "^0.1.4",

My server is a Meteor app @ [email protected] and using the meteor/apollo integration, so the graphql server is based on express.

[cfnelson]

@joncursi I was having a similar issue Error: Can't set headers after they are sent. after clearing my node_modules and reinstalling.

I was able to resolve it by installing "graphql-server-express": "1.0.0",. Something is breaking on "graphql-server-express": "1.0.2", for me.

[mklopets]

Can you provide a reduced test case for your setup that throws this error?

[VladDubrovskis]

We run into similar issue and rolled back to v1.0.0 for now. It seems to be caused by this change:
3d03295#diff-93774063e5fc49e60474cd9b82249731

Our use case that was breaking, is that we had a 404 middleware, however as res.end() was called by GraphQL, the 404 middleware was throwing error.

In theory, any middleware that you try to apply to all requests that might be modifying headers will break

[ArnaudRinquin]

Our app spits the same error after upgrading to 1.0.2 but, surprisingly, it does not break anything.

Here is the stack-trace:

Error: Can't set headers after they are sent.
  at validateHeader (_http_outgoing.js:504:11)
  at ServerResponse.setHeader (_http_outgoing.js:511:3)
  at ServerResponse.header (/tmp/node_modules/express/lib/response.js:719:10)
  at ServerResponse.send (/tmp/node_modules/express/lib/response.js:164:12)
  at ServerResponse.json (/tmp/node_modules/express/lib/response.js:250:15)
  at ServerResponse.send (/tmp/node_modules/express/lib/response.js:152:21)
  at /app/src/app.js:82:9
  at Layer.handle_error (/tmp/node_modules/express/lib/router/layer.js:71:5)
  at trim_prefix (/tmp/node_modules/express/lib/router/index.js:310:13)
  at /tmp/node_modules/express/lib/router/index.js:280:7
  at Function.process_params (/tmp/node_modules/express/lib/router/index.js:330:12)
  at next (/tmp/node_modules/express/lib/router/index.js:271:10)
  at /app/src/app.js:75:5
  at Layer.handle [as handle_request] (/tmp/node_modules/express/lib/router/layer.js:95:5)
  at trim_prefix (/tmp/node_modules/express/lib/router/index.js:312:13)
  at /tmp/node_modules/express/lib/router/index.js:280:7
  at Function.process_params (/tmp/node_modules/express/lib/router/index.js:330:12)
  at next (/tmp/node_modules/express/lib/router/index.js:271:10)
  at /tmp/node_modules/express/lib/router/index.js:618:15
  at next (/tmp/node_modules/express/lib/router/index.js:256:14)
  at /tmp/node_modules/apollo-server-express/dist/expressApollo.js:22:13
  at <anonymous>

Meaningful versions:

body-parser: "1.15.2"
dataloader: "^1.3.0"
debug: "^2.2.0"
express: "4.14.0"
express-graphql: "^0.6.6"
graphql: "^0.10.5"
graphql-redis-subscriptions-async-iterator: "^1.2.0"
graphql-server-express: "^1.0.0"
graphql-subscriptions: "^0.4.4"
graphql-tools: "^1.1.0"
graphql-type-json: "^0.1.4"
morgan: "1.7.0"
optics-agent: "^1.1.6"
request: "2.77.0"
subscriptions-transport-ws: "^0.8.1"

[goldo]

same for us here ! Thanks the tip

[Friss]

Here's a small example of the error. Any middleware after your GraphQL endpoint will be run, such as 404 / error handlers. These handlers are also generated as part of the express generator.

https://gist.github.com/Friss/90604b5f53ad4bb38146a8f49c730c13

[freiksenet]

We've reverted the patch that caused the problems. I'm very sorry for any inconvinience!

[frederikhors]

The problem is still there: #1523

Any hint?

[LazerJesus]

+1

[jakec-dev]

+1 same issue here

[arvi]

Same issue. https://stackoverflow.com/questions/58321093/graphql-clearing-session-cookie-results-to-cannot-set-headers-after-they-are-sen

[dmitrijs-pavlovs-dev]

Same here ericmakesapps/graphql-passport#36

[gaurav-bothra]

+1 same issue here
#4527

[marcoantoni0]

+1

[grantmontgomery]

Same issue too I'm trying to write a "Set-Cookie" header in my response object after logging in a user.

[alicerocheman]

Still encountering this issue.
The app works, but my server console keeps giving me this error.
Specifically:

[1] error - Error: write EPIPE
[1] error - Error: read ECONNRESET
[1] Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
[1]     at new NodeError (node:internal/errors:371:5)
[1]     at ServerResponse.setHeader (node:_http_outgoing:576:11)
[1]     at NodeNextResponse.setHeader (/Users/username/Dev/project/front/app/node_modules/next/dist/server/base-http/node.js:56:19)
[1]     at DevServer.renderError (/Users/username/Dev/project/front/app/node_modules/next/dist/server/base-server.js:1134:17)
[1]     at DevServer.renderError (/Users/username/Dev/project/front/app/node_modules/next/dist/server/next-server.js:493:22)
[1]     at DevServer.run (/Users/username/Dev/project/front/app/node_modules/next/dist/server/dev/next-dev-server.js:452:35)
[1]     at processTicksAndRejections (node:internal/process/task_queues:96:5)
[1]     at async DevServer.handleRequest (/Users/username/Dev/project/front/app/node_modules/next/dist/server/base-server.js:307:20) {
[1]   code: 'ERR_HTTP_HEADERS_SENT'
[1] }

conf:

    "@apollo/client": "^3.5.9",
    "next": "^12.1.0",

[glasser]

@alicerocheman Sorry you're running into this, but we won't be able to help without a full reproduction recipe that lets us see it ourselves without any creativity (eg, something starting with git clone or using codesandbox.io). It's probably a subtle interplay between NextJS, Apollo Server, and your own app code.

[leonard-henriquez]

I faced this issue and I found various examples of this error.
All those examples use Apollo server but they use different frameworks.
So, could this issue come from Apollo Server ?

• https://gist.github.com/Friss/90604b5f53ad4bb38146a8f49c730c13
• How to use express-session with nest/graphql  #4527
• Supertokens NestJs GraphQl - Cannot set headers after they are sent to the client supertokens/supertokens-node#331

Is this enough to investigate this issue @glasser ?

NB: the snipped provided by @porcellus on the SuperTokens issue offer a solution to this problem in their specific use case. Could it be used to solve this more general issue ?

[glasser]

No, we really need to be given an example that we can run without creativity and see exactly what's happening. (Many of the ones you have linked are from very old versions of Apollo Server — the first one is from Apollo Server v1, I think. The entire way that AS connects to web frameworks has been reworked multiple times since then; if the issue can't be reproduced in AS v4 then there's not much we're going to do.)

It sounds like the common thread involves doing some sort of error handling that sends a response; perhaps the error handling is firing in cases where the response has already been sent?