grpc-ecosystem/grpc-gateway

Unsupported HEAD call to known URL does not return error response body.

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#1,680 opened on Sep 21, 2020

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bughelp wanted

Description

🐛 Bug Report

When performing a HTTP call using an unsupported method, for example when making a POST request to a URL that only supports GET, I get a http-501-error-response from the gateway. The response body contains the grpc error code 12 ("Unimplemented") with the message "Method Not Allowed".

When performing a HEAD-call to the same get-only-URL, I expect the same error response. What happens is that the http request fails with 501 (which is correct), but the response body stays empty. According to the documentation, the HEAD call should not have any special behaviour, so I expect the body to contain the same error details. An error-response-body should never be empty. Docs: https://cloud.google.com/service-infrastructure/docs/service-management/reference/rpc/google.api#special-notes

To Reproduce

  1. Define a gRPC endpoint with only a GET-http-mapping (or any other method).
  2. Generate and start the grpc-gateway
  3. Perform a http HEAD-call to the same URL.
  4. The response (status 501) will have an empty body.

Your Environment

Im using github.com/grpc-ecosystem/grpc-gateway/v2 v2.0.0-beta.4

Contributor guide

Tech stack
go
Domain
backendapi
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Go programminggRPC conceptsHTTP methods
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the grpc gateway codebase to understand how unsupported HTTP methods are handled. Look at the gateway's HTTP handler, especially for HEAD requests. The issue mentions that a GET only endpoint returns an empty body for HEAD requests, while POST returns error details. Check the relevant source files in the runtime or gateway packages. Refer to the Google documentation link provided for expected behavior.