"TypeError: handler is not a function at Server" deploying to Google Cloud Run #49338
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I'm experimenting with Google Cloud Run for a Next.js deploy and I'm experiencing the same issue. Interestingly, it happens sporadically. |
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I tried a lot of things. Eventually I downgraded to next 13.3.4. At this time I am no longer able to product this mysterious 500. I have also not been able to product this error locally. |
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Running into the same issue. Gonna try changing min instances to 1 to reduce cold starts. |
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Experiencing the same issue on AWS Amplify: aws-amplify/amplify-hosting#3466 |
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I am also having this issue |
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Same error on Google Cloud Run. I've downgraded to nextjs 13.3.4 as well and I haven't seen it again. Though, I am reticent to say it fixes it because it was so sporadic. |
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Okay, so I have a somewhat good idea of what's happening. When the docker container starts, the handler takes a few seconds to init. I don't know why it takes it that long, but it does. The option, for now, is to leave the minimum server instance at 1 to avoid cold stars. To prove this, limit each container to a maximum number of 10 connections, then call the web page with a fetch of 10+ times. It fails when the tenth connection is hit, and a new container has to be spun up. |
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Good find @vamuscari. Another solution might be to set a startup probe maybe? Worth a try |
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PR with recommended fix: #49548 |
…t handler is ready (#49548) ### Fixing a bug Fixes #49536 Fixes #49338 ### What? Starting on next.js 13.4.0, the `server.js` file created by the standalone output is incorrect because it does not wait until the Next handler is ready before node http server starts accepting requests. Initial requests will produce the following error: ``` TypeError: handler is not a function at Server.<anonymous> (/tmp/app/server.js:29:11) at Server.emit (node:events:513:28) at parserOnIncoming (node:_http_server:998:12) at HTTPParser.parserOnHeadersComplete (node:_http_common:128:17) ``` ### Why? The creation of the next server takes roughly 800ms on a basic hello world app which causes the initial requests to fail because the `handler` variable is not initialized. ### Solution This changes the order of code so that Next Server is initialized before the Node HTTP server and awaits until the promise is completed to kick off the HTTP server. ### Alternative code ```js let handler; const server = http.createServer(async (req, res) => { try { await waitUntilHandlerIsReady(); // <---- wait here await handler(req, res); } catch (err) { console.error("Failed to call handler", err); res.statusCode = 500; res.end("Internal Server Error"); } }); async function waitUntilHandlerIsReady() { if (!handler) { await new Promise((resolve) => setTimeout(resolve, 200)); await waitUntilHandlerIsReady(); } } ``` --------- Co-authored-by: Tim Neutkens <tim@timneutkens.nl> Co-authored-by: JJ Kasper <jj@jjsweb.site>
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This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you. |
Verify canary release
Provide environment information
Operating System: Platform: darwin Arch: arm64 Version: Darwin Kernel Version 22.3.0: Mon Jan 30 20:39:46 PST 2023; root:xnu-8792.81.3~2/RELEASE_ARM64_T6020 Binaries: Node: 18.15.0 npm: 9.5.0 Yarn: 1.22.19 pnpm: N/A Relevant packages: next: 13.4.1-canary.2 eslint-config-next: N/A react: 18.2.0 react-dom: 18.2.0Which area(s) of Next.js are affected? (leave empty if unsure)
Middleware / Edge (API routes, runtime), Standalone mode (output: "standalone")
Link to the code that reproduces this issue
https://github.com/vercel/next.js/tree/canary/examples/with-docker
To Reproduce
docker build -t eu.gcr.io/{PROJECT-ID}/nextjs-docker .docker push eu.gcr.io/{PROJECT-ID}/nextjs-dockerDescribe the Bug
Everytime Cloud Run service cold starts, you will get an "Internal Server Error".
This is the error printed in the logs:
It looks like the server receives a request just before the handler is initialized with the function "createServerHandler".
If you refresh the page sometimes the error disappears and the page is shown correctly. This seems an error that occurs only when the service cold starts.
Expected Behavior
The page is shown without any error.
Which browser are you using? (if relevant)
No response
How are you deploying your application? (if relevant)
No response
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