Bug: External NGINX Reverse Proxy (1.26.3) returns 405 Not Allowed on POST requests to nested containers #214
Description
Description
We are encountering a 405 Not Allowed error when attempting to make POST requests through our external NGINX reverse proxy (nginx/1.26.3) to an API endpoint hosted inside a nested container architecture.
Architecture Example
The traffic flows through an external proxy before hitting the containerized environments. For example, using a host container named pmm-test:
Internet -> os.mieweb.org (NGINX 1.26.3) -> pmm-test (Outer Container) -> Inner Container (API Service)
The Issue
When sending a POST request to an API endpoint on the inner container, the outermost NGINX proxy intercepts the request and rejects it with a 405 Not Allowed status code, rather than using proxy_pass to route it upstream to pmm-test.
Steps to Reproduce
Send a POST request to the proxy endpoint with a standard payload targeting the nested service:
curl -v -X POST -H "Authorization: Basic <redacted>" \
-H "Content-Type: application/x-protobuf" \
https://pmm-test.os.mieweb.org/victoriametrics/api/v1/writeActual Output (Snippet):
The response headers and body explicitly show the external proxy terminating the request:
< HTTP/2 405
< server: nginx/1.26.3
< content-type: text/html
...
<html>
<head><title>405 Not Allowed</title></head>
<body>
<center><h1>405 Not Allowed</h1></center>
<hr><center>nginx/1.26.3</center>
</body>
</html>Expected Behavior
The external NGINX proxy (os.mieweb.org) should successfully route the POST request to the upstream pmm-test service without restricting the HTTP method or attempting to serve the endpoint as a static file.
Additional Context
The error page identifies nginx/1.26.3, confirming the block is happening at the external proxy layer, not within the internal pmm-test application containers.
In NGINX, a 405 Not Allowed often occurs when a location block is misconfigured to serve static files for an API route, or if there is a missing proxy_pass directive for the specific path handling POST methods.