feat: emit status code 499 for requests canceled by the client

Author: alnr

clientclosed.go

@@ -0,0 +1,13 @@
+// Copyright © 2023 Ory Corp
+// SPDX-License-Identifier: Apache-2.0
+
+package herodot
+
+// StatusClientClosedRequest (reported as 499 Client Closed Request) is a faux
+// but de-facto standard HTTP status code first used by nginx, indicating the
+// client canceled the request. Because the client canceled, it is never
+// actually reported back to them. 499 is useful purely in logging, tracing,
+// etc.
+//
+// http://nginx.org/en/docs/dev/development_guide.html
+const StatusClientClosedRequest int = 499

json.go

@@ -5,6 +5,7 @@ package herodot
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	stderr "errors"
 	"net/http"
@@ -83,6 +84,10 @@ func (h *JSONWriter) WriteCode(w http.ResponseWriter, r *http.Request, code int,
 		code = http.StatusOK
 	}
 
+	if errors.Is(r.Context().Err(), context.Canceled) {
+		code = StatusClientClosedRequest
+	}
+
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
 	w.WriteHeader(code)
 	_, _ = w.Write(bs.Bytes())
@@ -114,6 +119,10 @@ func (h *JSONWriter) WriteErrorCode(w http.ResponseWriter, r *http.Request, code
 		code = http.StatusInternalServerError
 	}
 
+	if errors.Is(r.Context().Err(), context.Canceled) {
+		code = StatusClientClosedRequest
+	}
+
 	if !o.noLog {
 		// All errors land here, so it's a really good idea to do the logging here as well!
 		h.Reporter.ReportError(r, code, coalesceError(err), "An error occurred while handling a request")

json_test.go

@@ -5,13 +5,15 @@ package herodot
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	stderr "errors"
 	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
@@ -260,3 +262,30 @@ func TestWriteCodeJSONUnescapedHTML(t *testing.T) {
 	assert.Equal(t, fmt.Sprintf("\"%s\"\n", foo), string(result))
 	assert.Equal(t, http.StatusOK, resp.StatusCode)
 }
+
+func TestCanceledJSON(t *testing.T) {
+	h := NewJSONWriter(nil)
+	rec := httptest.NewRecorder()
+	done := make(chan struct{})
+	ts := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+		defer close(done)
+		<-r.Context().Done()
+		h.WriteError(rec, r, errors.New("some unrelated error"))
+	}))
+	defer ts.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
+	defer cancel()
+	req, err := http.NewRequestWithContext(ctx, "GET", ts.URL, nil)
+	require.NoError(t, err)
+
+	_, err = ts.Client().Do(req)
+	require.ErrorIs(t, err, context.DeadlineExceeded)
+
+	<-done
+	resp := rec.Result()
+	body, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+	assert.Contains(t, string(body), "some unrelated error")
+	assert.Equal(t, 499, resp.StatusCode)
+}

plain.go

@@ -4,6 +4,7 @@
 package herodot
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 
@@ -43,6 +44,10 @@ func (h *TextWriter) WriteCode(w http.ResponseWriter, r *http.Request, code int,
 		code = http.StatusOK
 	}
 
+	if errors.Is(r.Context().Err(), context.Canceled) {
+		code = StatusClientClosedRequest
+	}
+
 	w.Header().Set("Content-Type", h.contentType)
 	w.WriteHeader(code)
 	fmt.Fprintf(w, "%s", e)
@@ -75,6 +80,10 @@ func (h *TextWriter) WriteErrorCode(w http.ResponseWriter, r *http.Request, code
 		code = http.StatusInternalServerError
 	}
 
+	if errors.Is(r.Context().Err(), context.Canceled) {
+		code = StatusClientClosedRequest
+	}
+
 	// All errors land here, so it's a really good idea to do the logging here as well!
 	h.Reporter.ReportError(r, code, err, "An error occurred while handling a request")