What could be causing the "502 Gateway" error specifically for POST requests in my NextJs app hosted on Firebase?

Question

What could be causing the "502 Gateway" error specifically for POST requests in my NextJs app hosted on Firebase?

I've encountered an issue while trying to build an API with the NextJs framework and hosting it on Firebase (Hosting and Functions). The GET requests work fine, but when I try to send a POST request, I keep getting a "502 Bad Gateway" error.

To replicate this problem, simply download and deploy the example provided by the NextJs development team:

Create a new project on Firebase console
Install the "with Firebase hosting" example
Change the project name in the .firebaserc (line 3) file
Create a folder named "api" within the "pages" folder

Create a file named "hello.js" inside the "api" folder and include the code snippet provided

export default async (req, res) => {
  const {
    body,
    method
  } = req;

  console.log("method :>> ", method);
  console.log("body :>> ", body);

  switch (method) {
  case "POST":
    res.status(200).end(`Method ${method} supported!`);
    break;
  default:
    res.setHeader("Allow", ["POST"]);
    res.status(405).end(`Method ${method} Not Allowed`);
  }
};

Deploy the application
Send a GET request to "https://[project-name].web.app/api/hello" to confirm its functionality
Send a POST request to "https://[project-name].web.app/api/hello" and observe the error

Have you faced a similar issue?

I've invested 2 days researching articles, watching videos, and experimenting with different configurations. You can even update the firebaseFunctions to include a console.log and verify that the POST request is received by the Firebase Cloud Function, but the NextJs server fails to pass it to our API like it does for GET requests. Unfortunately, this is beyond my current skill set...

Refer to the image link for the expected output. The POST request should ideally return a 200 status along with the message "Method POST is supported!".

https://i.stack.imgur.com/itxoQ.png

firebase google-cloud-functions next.js firebase-hosting

Answer 1

Answer №1

After some thorough investigation, I finally uncovered the root of the problem. It appears that PUT and PATCH requests are experiencing the same issue, indicating that it is related to the request body. To my frustration, I later stumbled upon a discussion in Issue #7960, where others were facing the exact same challenge.

In essence, the request body is being processed twice - first by https.onRequest() and then by nextjsHandle(). This redundant parsing causes the raw-body module (within nextjsHandle()) to wait endlessly for 'data' events that never materialize.

Unfortunately, there is no direct way to disable the body parsing initiated by https.onRequest(). Instead, it must be deactivated on the next.js side. Regrettably, no overarching switch exists in next.config.js, so each API route (located in pages/api) requires individual modification (unless a proposed fix in PR #16169 is implemented).

To deactivate body parsing for a specific route, insert the following snippet into the file:

export const config = {
  api: {
    // disables call to body parsing module
    bodyParser: false,
  }
};

As noted in Issue #7960 by @rscotten, consider enabling next dev during application development; hence, enable it during local usage but disable when deploying. Achieve this with:

export const config = {
  api: {
    // disables call to body parsing module while deployed
    bodyParser: process.env.NODE_ENV !== 'production',
  }
};

Implementing these adjustments in hello.js results in the following:

export default async (req, res) => {
  const {
    body,
    method
  } = req;

  console.log("method :>> ", method);
  console.log("body :>> ", body);

  switch (method) {
  case "POST":
    res.status(200).end(`Method ${method} supported!`);
    break;
  default:
    res.setHeader("Allow", ["POST"]);
    res.status(405).end(`Method ${method} Not Allowed`);
  }
};

export const config = {
  api: {
    // disable nextjs's body parser while deployed
    // (as body parsing is handled by `https.onRequest()`),
    // but enable it for local development using `next dev`
    bodyParser: process.env.NODE_ENV !== 'production',
  }
};

Answer 2

After some thorough investigation, I finally uncovered the root of the problem. It appears that PUT and PATCH requests are experiencing the same issue, indicating that it is related to the request body. To my frustration, I later stumbled upon a discussion in Issue #7960, where others were facing the exact same challenge.

In essence, the request body is being processed twice - first by https.onRequest() and then by nextjsHandle(). This redundant parsing causes the raw-body module (within nextjsHandle()) to wait endlessly for 'data' events that never materialize.

Unfortunately, there is no direct way to disable the body parsing initiated by https.onRequest(). Instead, it must be deactivated on the next.js side. Regrettably, no overarching switch exists in next.config.js, so each API route (located in pages/api) requires individual modification (unless a proposed fix in PR #16169 is implemented).

To deactivate body parsing for a specific route, insert the following snippet into the file:

export const config = {
  api: {
    // disables call to body parsing module
    bodyParser: false,
  }
};

As noted in Issue #7960 by @rscotten, consider enabling next dev during application development; hence, enable it during local usage but disable when deploying. Achieve this with:

export const config = {
  api: {
    // disables call to body parsing module while deployed
    bodyParser: process.env.NODE_ENV !== 'production',
  }
};

Implementing these adjustments in hello.js results in the following:

export default async (req, res) => {
  const {
    body,
    method
  } = req;

  console.log("method :>> ", method);
  console.log("body :>> ", body);

  switch (method) {
  case "POST":
    res.status(200).end(`Method ${method} supported!`);
    break;
  default:
    res.setHeader("Allow", ["POST"]);
    res.status(405).end(`Method ${method} Not Allowed`);
  }
};

export const config = {
  api: {
    // disable nextjs's body parser while deployed
    // (as body parsing is handled by `https.onRequest()`),
    // but enable it for local development using `next dev`
    bodyParser: process.env.NODE_ENV !== 'production',
  }
};

What could be causing the "502 Gateway" error specifically for POST requests in my NextJs app hosted on Firebase?

Answer №1

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