nginx protocol_error ai_generated true

upstream sent too big header while reading response header from upstream, client: 10.0.0.1, server: example.com, upstream: "http://127.0.0.1:8080"

ID: nginx/proxy-buffer-size-too-small

Also available as: JSON · Markdown · 中文
95%Fix Rate
88%Confidence
1Evidence
2024-08-12First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
nginx/1.18.0 active — — —
nginx/1.20.0 active — — —
nginx/1.24.0 active — — —
nginx/1.26.0 active — — —

Root Cause

The upstream server's response headers exceed the default proxy_buffer_size (4KB), causing nginx to reject the response with a 502 error.

generic

中文

上游服务器的响应标头超过默认的 proxy_buffer_size（4KB），导致 nginx 拒绝响应并返回 502 错误。

Official Documentation

https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_buffer_size

Workarounds

  1. 95% success Increase proxy_buffer_size to 8K or larger (e.g., 16K) in the location or server block: `proxy_buffer_size 16k;` 
    Increase proxy_buffer_size to 8K or larger (e.g., 16K) in the location or server block: `proxy_buffer_size 16k;`
  2. 90% success Also increase proxy_buffers to match for consistency: `proxy_buffers 8 16k;` 
    Also increase proxy_buffers to match for consistency: `proxy_buffers 8 16k;`
  3. 70% success If the large header is due to many cookies, consider using a custom header compression or reducing cookie size at the application level as a long-term fix. 
    If the large header is due to many cookies, consider using a custom header compression or reducing cookie size at the application level as a long-term fix.

中文步骤

  1. 在 location 或 server 块中将 proxy_buffer_size 增加到 8K 或更大（例如 16K）：`proxy_buffer_size 16k;`
  2. 同时增加 proxy_buffers 以保持一致：`proxy_buffers 8 16k;`
  3. 如果大标头是由于过多 cookie 引起的，请考虑在应用程序级别使用自定义标头压缩或减少 cookie 大小作为长期修复。

Dead Ends

Common approaches that don't work:

  1. 70% fail

    proxy_buffers controls the number and size of buffers for the response body, not the initial header buffer.

  2. 60% fail

    proxy_buffering off affects body buffering, not header buffering; the header buffer size is always limited by proxy_buffer_size.

  3. 40% fail

    While this can fix the symptom, it requires application changes that may break features like session management or authentication.