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nextjs - 💡(How to fix) Fix Caching issue where the ETag is generated ONLY based on the response body

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Today I used patch-package to patch [email protected] for the project I'm working on.

This patch resolves a specific caching issue where the ETag is generated ONLY based on the response body, causing:

THIS PATCH DOES:

  • Adds: const origin = req.headers.origin;

Code Example

diff --git a/node_modules/next/dist/server/api-utils/node/api-resolver.js b/node_modules/next/dist/server/api-utils/node/api-resolver.js
index c2c9bdc..ea6af17 100644
--- a/node_modules/next/dist/server/api-utils/node/api-resolver.js
+++ b/node_modules/next/dist/server/api-utils/node/api-resolver.js
@@ -60,13 +60,14 @@ function getMaxContentLength(responseLimit) {
         body.pipe(res);
         return;
     }
+    const origin = req.headers.origin;
     const isJSONLike = [
         'object',
         'number',
         'boolean'
     ].includes(typeof body);
     const stringifiedBody = isJSONLike ? JSON.stringify(body) : body;
-    const etag = (0, _etag.generateETag)(stringifiedBody);
+    const etag = (0, _etag.generateETag)(stringifiedBody.concat(origin || ''));
     if ((0, _sendpayload.sendEtagResponse)(req, res, etag)) {
         return;
     }
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Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch [email protected] for the project I'm working on.

This patch resolves a specific caching issue where the ETag is generated ONLY based on the response body, causing:

  1. CORS Issues: Different origins receive the same ETag for identical responses.
  2. Incorrect Cache: Cached responses may be served to different origins.
  3. Problematic Headers: Origin is not considered in ETag generation.

THIS PATCH DOES:

  • Adds: const origin = req.headers.origin;

  • Modifies: const etag = (0, _etag.generateETag)(stringifiedBody.concat(origin || ''));

The FALLBACK (|| '') avoids errors if origin is undefined/null and maintains functionality even without an origin header. RESULT: Unique ETag per origin, avoiding incorrect cross-origin caching.

Here is the diff that solved my problem:

diff --git a/node_modules/next/dist/server/api-utils/node/api-resolver.js b/node_modules/next/dist/server/api-utils/node/api-resolver.js
index c2c9bdc..ea6af17 100644
--- a/node_modules/next/dist/server/api-utils/node/api-resolver.js
+++ b/node_modules/next/dist/server/api-utils/node/api-resolver.js
@@ -60,13 +60,14 @@ function getMaxContentLength(responseLimit) {
         body.pipe(res);
         return;
     }
+    const origin = req.headers.origin;
     const isJSONLike = [
         'object',
         'number',
         'boolean'
     ].includes(typeof body);
     const stringifiedBody = isJSONLike ? JSON.stringify(body) : body;
-    const etag = (0, _etag.generateETag)(stringifiedBody);
+    const etag = (0, _etag.generateETag)(stringifiedBody.concat(origin || ''));
     if ((0, _sendpayload.sendEtagResponse)(req, res, etag)) {
         return;
     }

<em>This issue body was partially generated by patch-package.</em>

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#api#callback error#memory management#API rate limit#retriever error

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