nginx protocol_error ai_generated true

upstream sent invalid Content-Length: 0 with non-empty body while reading response header from upstream, client: 10.0.0.1, server: example.com

ID: nginx/upstream-sent-invalid-content-length-zero-body

Also available as: JSON · Markdown · 中文
74%Fix Rate
83%Confidence
1Evidence
2024-06-22First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
nginx 1.18.0 active — — —
nginx 1.20.1 active — — —
nginx 1.22.0 active — — —
nginx 1.24.0 active — — —

Root Cause

Upstream sends a Content-Length of 0 but then includes a non-empty response body, causing nginx to detect a mismatch and abort.

generic

中文

上游发送了 Content-Length 为 0 但随后包含了非空的响应主体，导致 nginx 检测到不匹配并终止。

Official Documentation

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

Workarounds

  1. 85% success Fix the upstream application to correctly set Content-Length to the actual body size. For example, in a Go HTTP handler, ensure Content-Length matches the body: func handler(w http.ResponseWriter, r *http.Request) { body := []byte("Hello") w.Header().Set("Content-Length", strconv.Itoa(len(body))) w.Write(body) } Avoid hardcoding Content-Length to 0 when writing a body. 
    Fix the upstream application to correctly set Content-Length to the actual body size. For example, in a Go HTTP handler, ensure Content-Length matches the body:
func handler(w http.ResponseWriter, r *http.Request) {
    body := []byte("Hello")
    w.Header().Set("Content-Length", strconv.Itoa(len(body)))
    w.Write(body)
}
Avoid hardcoding Content-Length to 0 when writing a body.
  2. 72% success Use nginx's proxy_hide_header Content-Length; to remove the upstream's Content-Length header, forcing nginx to use chunked encoding or calculate length from the actual body. Example: location / { proxy_pass http://upstream; proxy_hide_header Content-Length; } 
    Use nginx's proxy_hide_header Content-Length; to remove the upstream's Content-Length header, forcing nginx to use chunked encoding or calculate length from the actual body. Example:
location / {
    proxy_pass http://upstream;
    proxy_hide_header Content-Length;
}

中文步骤

  1. Fix the upstream application to correctly set Content-Length to the actual body size. For example, in a Go HTTP handler, ensure Content-Length matches the body:
func handler(w http.ResponseWriter, r *http.Request) {
    body := []byte("Hello")
    w.Header().Set("Content-Length", strconv.Itoa(len(body)))
    w.Write(body)
}
Avoid hardcoding Content-Length to 0 when writing a body.
  2. Use nginx's proxy_hide_header Content-Length; to remove the upstream's Content-Length header, forcing nginx to use chunked encoding or calculate length from the actual body. Example:
location / {
    proxy_pass http://upstream;
    proxy_hide_header Content-Length;
}

Dead Ends

Common approaches that don't work:

  1. Set proxy_request_buffering off; 95% fail

    Request buffering affects client request body, not response body handling from upstream.

  2. Increase proxy_buffer_size 93% fail

    Buffer size does not affect the Content-Length validation logic; the error is about header-body mismatch.

  3. Disable chunked transfer encoding with proxy_set_header Transfer-Encoding ''; 88% fail

    This modifies request headers to upstream, not the response; the error is in the response.