api_server: convert the VmmActionError to a JSON object

src/api_server/src/parsed_request.rs

@@ -92,7 +92,9 @@ impl ParsedRequest {
                     vmm_action_error
                 );
                 let mut response = Response::new(Version::Http11, StatusCode::BadRequest);
-                response.set_body(Body::new(vmm_action_error.to_string()));
+                response.set_body(Body::new(ApiServer::json_fault_message(
+                    vmm_action_error.to_string(),
+                )));
                 response
             }
         }
@@ -465,18 +467,20 @@ mod tests {
         assert_eq!(&buf[..], expected_response.as_bytes());
 
         // Error.
-        let mut buf: [u8; 160] = [0; 160];
-        let response = ParsedRequest::convert_to_response(Err(VmmActionError::from(
-            StartMicrovmError::EventFd,
-        )));
+        let error = VmmActionError::from(StartMicrovmError::EventFd);
+        let mut buf: [u8; 185] = [0; 185];
+        let json = ApiServer::json_fault_message(error.to_string());
+        let response = ParsedRequest::convert_to_response(Err(error));
         assert!(response.write_all(&mut buf.as_mut()).is_ok());
+
         let expected_response = format!(
             "HTTP/1.1 400 \r\n\
              Server: Firecracker API\r\n\
              Connection: keep-alive\r\n\
              Content-Type: application/json\r\n\
-             Content-Length: 42\r\n\r\n{}",
-            VmmActionError::from(StartMicrovmError::EventFd).to_string()
+             Content-Length: {}\r\n\r\n{}",
+            json.len(),
+            json,
         );
         assert_eq!(&buf[..], expected_response.as_bytes());
     }

tests/integration_tests/functional/test_logging.py

@@ -118,6 +118,23 @@ def test_error_logs(test_microvm_with_ssh):
     )
 
 
+def test_log_config_failure(test_microvm_with_api):
+    """Check passing invalid FIFOs is detected and reported as an error."""
+    microvm = test_microvm_with_api
+    microvm.spawn()
+    microvm.basic_config()
+
+    response = microvm.logger.put(
+        log_fifo='invalid log fifo',
+        metrics_fifo='invalid metrics fifo',
+        level='Info',
+        show_level=True,
+        show_log_origin=True,
+    )
+    assert microvm.api_session.is_status_bad_request(response.status_code)
+    assert response.json()['fault_message']
+
+
 def log_file_contains_strings(log_fifo, string_list):
     """Check if the log file contains all strings in string_list.