fix(api): classify client-cancelled requests as 499 instead of 500

pkg/modules/api/middlewares.go

@@ -86,13 +86,37 @@ func ParseError(err error) (int, string) {
 	return http.StatusInternalServerError, http.StatusText(http.StatusInternalServerError)
 }
 
+// statusClientClosedRequest is the non-standard 499 status (nginx convention)
+// recorded when the client aborts the request before it completes. It keeps
+// such outcomes out of the 5xx range in the access log and Prometheus metrics.
+const statusClientClosedRequest = 499
+
+// requestCanceled reports whether err is the result of the client aborting the
+// request rather than a server-side failure. It requires both that err wraps
+// [context.Canceled] and that the request context itself was canceled, so a
+// context.Canceled originating elsewhere still surfaces as an internal error.
+// A server-side timeout is [context.DeadlineExceeded], mapped to 503 by
+// [ParseError], and is deliberately not treated as a client abort.
+// See https://github.com/gotenberg/gotenberg/issues/1627.
+func requestCanceled(c echo.Context, err error) bool {
+	return errors.Is(err, context.Canceled) && errors.Is(c.Request().Context().Err(), context.Canceled)
+}
+
 // httpErrorHandler is the centralized HTTP error handler. It parses the error,
 // returns a response as "text/plain; charset=UTF-8".
 func httpErrorHandler() echo.HTTPErrorHandler {
 	return func(err error, c echo.Context) {
 		logger := c.Get("logger").(*slog.Logger)
-		status, message := ParseError(err)
 
+		if requestCanceled(c, err) {
+			// The client is gone, so writing a body would only fail and add
+			// noise. Record the status so the access log and metrics classify
+			// it as a client abort rather than an internal error.
+			c.Response().WriteHeader(statusClientClosedRequest)
+			return
+		}
+
+		status, message := ParseError(err)
 		c.Response().Header().Add(echo.HeaderContentType, echo.MIMETextPlainCharsetUTF8)
 
 		err = c.String(status, message)
@@ -263,9 +287,15 @@ func telemetryMiddleware(logger *slog.Logger, serverName, correlationIdHeader st
 			finishTime := time.Now()
 
 			status := c.Response().Status
+			canceled := false
 			if err != nil {
-				parsedStatus, _ := ParseError(err)
-				status = parsedStatus
+				canceled = requestCanceled(c, err)
+				if canceled {
+					status = statusClientClosedRequest
+				} else {
+					parsedStatus, _ := ParseError(err)
+					status = parsedStatus
+				}
 
 				span.SetAttributes(attribute.String("error", err.Error()))
 				c.Error(err)
@@ -293,10 +323,15 @@ func telemetryMiddleware(logger *slog.Logger, serverName, correlationIdHeader st
 				With(slog.Int64("bytes_in", c.Request().ContentLength)).
 				With(slog.Int64("bytes_out", c.Response().Size))
 
-			if err != nil {
-				accessLogger.ErrorContext(ctx, err.Error())
-			} else {
+			switch {
+			case err == nil:
 				accessLogger.InfoContext(ctx, "request handled")
+			case canceled:
+				// A client abort is expected, not a server failure; keep it
+				// visible but out of the error stream.
+				accessLogger.InfoContext(ctx, err.Error())
+			default:
+				accessLogger.ErrorContext(ctx, err.Error())
 			}
 
 			additionalAttributes := []attribute.KeyValue{

pkg/modules/api/middlewares_test.go

@@ -1,6 +1,10 @@
 package api
 
 import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -10,6 +14,70 @@ import (
 	"github.com/labstack/echo/v4"
 )
 
+// TestRequestCanceled pins the client-abort discriminator: only a
+// context.Canceled that stems from the request context counts, so a server
+// timeout or an unrelated cancellation still surfaces as an internal failure.
+// See https://github.com/gotenberg/gotenberg/issues/1627.
+func TestRequestCanceled(t *testing.T) {
+	canceled, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	timedOut, cancelTimeout := context.WithDeadline(context.Background(), time.Now().Add(-time.Second))
+	defer cancelTimeout()
+
+	for _, tc := range []struct {
+		name   string
+		reqCtx context.Context
+		err    error
+		want   bool
+	}{
+		{"client abort", canceled, context.Canceled, true},
+		{"wrapped client abort", canceled, fmt.Errorf("convert to PDF: %w", context.Canceled), true},
+		{"canceled error but live request", context.Background(), context.Canceled, false},
+		{"canceled request but unrelated error", canceled, errors.New("boom"), false},
+		{"server timeout is not a client abort", timedOut, context.DeadlineExceeded, false},
+		{"no error", canceled, nil, false},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodPost, "/", nil).WithContext(tc.reqCtx)
+			c := echo.New().NewContext(req, httptest.NewRecorder())
+			if got := requestCanceled(c, tc.err); got != tc.want {
+				t.Fatalf("requestCanceled = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+// TestHttpErrorHandler_ClientClosedRequest ensures a client abort is recorded
+// as 499 rather than 500, and that a genuine failure keeps its status.
+func TestHttpErrorHandler_ClientClosedRequest(t *testing.T) {
+	canceled, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	for _, tc := range []struct {
+		name       string
+		reqCtx     context.Context
+		err        error
+		wantStatus int
+	}{
+		{"client abort", canceled, fmt.Errorf("convert to PDF: %w", context.Canceled), statusClientClosedRequest},
+		{"internal failure", context.Background(), errors.New("boom"), http.StatusInternalServerError},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodPost, "/", nil).WithContext(tc.reqCtx)
+			rec := httptest.NewRecorder()
+			c := echo.New().NewContext(req, rec)
+			c.Set("logger", slog.New(slog.DiscardHandler))
+
+			httpErrorHandler()(tc.err, c)
+
+			if rec.Code != tc.wantStatus {
+				t.Fatalf("status = %d, want %d", rec.Code, tc.wantStatus)
+			}
+		})
+	}
+}
+
 // TestOutputFilenameMiddleware pins the sanitizing of the
 // "Gotenberg-Output-Filename" header. The value reaches archive entry names and
 // a Content-Disposition header, so a path separator must never survive it.