Fallback to content type in error handler

.chloggen/13414-otlp-receiver-error-handler.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: otlpreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Error handler correctly fallbacks to content type
+
+# One or more tracking issues or pull requests related to the change
+issues: [13414]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/otlpreceiver/otlp_test.go

@@ -496,6 +496,35 @@ func TestOTLPReceiverInvalidContentEncoding(t *testing.T) {
 	}
 }
 
+func TestOTLPReceiverNoContentType(t *testing.T) {
+	addr := testutil.GetAvailableLocalAddress(t)
+
+	// Set the buffer count to 1 to make it flush the test span immediately.
+	recv := newHTTPReceiver(t, componenttest.NewNopTelemetrySettings(), addr, consumertest.NewNop())
+
+	require.NoError(t, recv.Start(context.Background(), componenttest.NewNopHost()), "Failed to start trace receiver")
+	t.Cleanup(func() { require.NoError(t, recv.Shutdown(context.Background())) })
+
+	url := fmt.Sprintf("http://%s%s", addr, defaultTracesURLPath)
+
+	t.Run("NoContentType", func(t *testing.T) {
+		body := bytes.NewBuffer([]byte(`{"key": "value"}`))
+
+		req, err := http.NewRequest(http.MethodPost, url, body)
+		require.NoError(t, err, "Error creating trace POST request: %v", err)
+
+		// Set invalid encoding to trigger an error
+		req.Header.Set("Content-Encoding", "invalid")
+
+		resp, err := http.DefaultClient.Do(req)
+		require.NoError(t, err, "Error posting to server: %v", err)
+		// Don't care about the response body, just check the content type
+		defer resp.Body.Close()
+
+		require.Equal(t, fallbackContentType, resp.Header.Get("Content-Type"), "Unexpected response Content-Type")
+	})
+}
+
 func TestGRPCNewPortAlreadyUsed(t *testing.T) {
 	addr := testutil.GetAvailableLocalAddress(t)
 	ln, err := net.Listen("tcp", addr)

receiver/otlpreceiver/otlphttp.go

@@ -195,7 +195,11 @@ func writeError(w http.ResponseWriter, encoder encoder, err error, statusCode in
 // by the OTLP protocol.
 func errorHandler(w http.ResponseWriter, r *http.Request, errMsg string, statusCode int) {
 	s := statusutil.NewStatusFromMsgAndHTTPCode(errMsg, statusCode)
-	switch getMimeTypeFromContentType(r.Header.Get("Content-Type")) {
+	contentType := r.Header.Get("Content-Type")
+	if contentType == "" {
+		contentType = fallbackContentType
+	}
+	switch getMimeTypeFromContentType(contentType) {
 	case pbContentType:
 		writeStatusResponse(w, pbEncoder, statusCode, s)
 		return