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If a partner’s webhook POST reaches your application as an empty GET after you move the endpoint, trace every request hop before changing the webhook code. A redirect, proxy setting, or internal error route can each affect what the application receives. The symptom alone does not identify which one is responsible.
Trace the request from the partner to your application
Record what happens at each hop, starting with the partner’s request and ending at the application. The key is to compare the method and body at the public edge with the method and body received by the application.
- Capture the partner’s first response. Record its status code and any
Locationheader. Follow the complete response chain rather than checking only the final URL. - Log each request hop. For every URL, note the method, whether a body is present, and—where your logs expose it—the body length. Mark whether the transition is an external redirect, a proxy pass, or internal routing.
- Compare edge and application observations. If the edge receives a POST with a body but the application receives an empty GET, the change happened somewhere between those observation points. If the edge already sees a GET or no body, investigate the partner’s request and redirect-following behavior as well.
- Check the migrated URL. Look for scheme or hostname changes, path rewrites, and trailing-slash canonicalization that may trigger a redirect. If the partner can be configured with the final canonical URL, use it to avoid an unnecessary redirect hop.
- Verify the live configuration. Inspect the configuration loaded by the deployed proxy or ingress controller, not just a file in the repository or a local copy.
For NGINX, the reverse-proxy documentation explains request forwarding and header behavior. NGINX may change the Host and Connection headers by default; proxy_set_header configures headers sent upstream. Those header changes are distinct from a method or body change, but can matter when checking how the upstream handles the request.
Check whether a redirect changed the POST
A redirect is a plausible lead after an endpoint migration, but “redirect” is not enough information to determine what happened. Capture the exact status code and confirm how the partner’s HTTP client handles that code, including whether it follows the redirect and what method and body it sends on the next request. Do not assume all 3xx responses preserve a POST and its payload.
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The ingress-nginx ConfigMap documentation lists redirect status options including 301, 302, 307, and 308, and describes 308 as preserving payload for methods such as POST. F5 NGINX’s advanced configuration with annotations also documents redirect settings. These references describe particular ingress products; check the controller, version, and settings actually serving your endpoint.
If NGINX is in the request path, inspect method and body handling
NGINX has separate controls for the upstream method, request body forwarding, and buffering. Check each rather than treating an empty body as proof that buffering dropped it.
proxy_pass_request_bodycontrols whether the client request body is passed to the upstream; its documented default ison.proxy_methodcan specify the method used for the upstream request. Check whether a configured override could account for the GET.proxy_request_bufferingcontrols whether NGINX reads the entire client body before sending it upstream or sends it as it arrives. Buffering is not the same as dropping the body.
See the NGINX proxy module documentation for these directives. Their relevance depends on whether NGINX is actually present in the deployed request path.
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NGINX documents a specific method-changing case: an error_page internal redirect to a URI changes methods other than GET and HEAD to GET. If the request enters error-page handling, inspect the applicable error_page configuration and trace whether it routes internally to a URI.
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This behavior is documented in the NGINX core module reference. It is not a general rule for every proxy rewrite or external redirect; do not attribute a POST-to-GET change to it without confirming that this internal route is involved.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Use the trace to narrow down the fault
- The partner follows a redirect: Compare the initial response’s status and
Locationwith the method and body on the redirected request. Confirm the partner client’s documented behavior or obtain a request trace. - The public edge receives POST with a body, but the application sees GET: Inspect proxy method overrides, request-body forwarding, and internal error-page routing between those points.
- The public edge receives GET or an empty body: Check the partner’s configured URL and its redirect-following behavior before focusing on application-side forwarding.
- Logs disagree or omit the body: Add safe request metadata logging at both observation points. Compare method, target URL, body presence or length, response status, and redirect location; avoid recording sensitive webhook payloads unnecessarily.
These observations identify where to investigate next, not a guaranteed root cause. Without the partner’s request trace, the full response chain, and the deployed configuration, the original symptom cannot establish which component changed the method or removed the body.
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