instance start: return the actual error on fail

Set the response body when InstanceStart fails to the error
received from the VMM. Also, set the status code to 500 (Internal
Server Error) or 400 (Bad Request) depending on error type.

Signed-off-by: Andreea Florescu <[email protected]>

Author: andreeaflorescu

api_server/src/request/mod.rs

@@ -108,7 +108,7 @@ pub enum Error {
     DriveOperationFailed(DriveError),
     GuestCIDAlreadyInUse,
     GuestMacAddressInUse,
-    InstanceStartFailed,
+    InstanceStartFailed(ErrorType, String),
     InvalidPayload,
     MicroVMAlreadyRunning,
     OpenTap(TapError),
@@ -118,6 +118,12 @@ pub enum Error {
     UpdateNotImplemented,
 }
 
+#[derive(Debug)]
+pub enum ErrorType {
+    UserError,
+    InternalError,
+}
+
 impl GenerateResponse for Error {
     fn generate_response(&self) -> hyper::Response {
         use self::Error::*;
@@ -131,10 +137,14 @@ impl GenerateResponse for Error {
                 StatusCode::BadRequest,
                 json_fault_message("The specified guest MAC address is already in use."),
             ),
-            InstanceStartFailed => json_response(
-                StatusCode::InternalServerError,
-                json_fault_message("The microVM failed to start."),
-            ),
+            InstanceStartFailed(ref error_type, ref error_msg) => {
+                let status_code = match error_type {
+                    ErrorType::InternalError => StatusCode::InternalServerError,
+                    ErrorType::UserError => StatusCode::BadRequest,
+                };
+
+                json_response(status_code, json_fault_message(error_msg))
+            }
             InvalidPayload => json_response(
                 StatusCode::BadRequest,
                 json_fault_message("The request payload is invalid."),
@@ -295,9 +305,14 @@ mod tests {
         ret = Error::GuestMacAddressInUse.generate_response();
         assert_eq!(ret.status(), StatusCode::BadRequest);
 
-        ret = Error::InstanceStartFailed.generate_response();
+        ret = Error::InstanceStartFailed(ErrorType::InternalError, "Dummy error".to_string())
+            .generate_response();
         assert_eq!(ret.status(), StatusCode::InternalServerError);
 
+        ret = Error::InstanceStartFailed(ErrorType::UserError, "Dummy error".to_string())
+            .generate_response();
+        assert_eq!(ret.status(), StatusCode::BadRequest);
+
         ret = Error::InvalidPayload.generate_response();
         assert_eq!(ret.status(), StatusCode::BadRequest);
 

vmm/src/lib.rs

@@ -54,7 +54,8 @@ use api_server::request::machine_configuration::{
 };
 use api_server::request::net::NetworkInterfaceBody;
 use api_server::request::{
-    Error as SyncError, GenerateResponse, OkStatus as SyncOkStatus, SyncOutcomeSender, SyncRequest,
+    Error as SyncError, ErrorType, GenerateResponse, OkStatus as SyncOkStatus, SyncOutcomeSender,
+    SyncRequest,
 };
 use data_model::vm::{
     description_into_implementation as rate_limiter_description_into_implementation,
@@ -1304,10 +1305,19 @@ impl Vmm {
                 .send(Box::new(SyncOkStatus::NoContent))
                 .map_err(|_| ())
                 .expect("one-shot channel closed"),
-            Err(_) => sender
-                .send(Box::new(SyncError::InstanceStartFailed))
-                .map_err(|_| ())
-                .expect("one-shot channel closed"),
+            Err(e) => {
+                let err_type = match e {
+                    Error::User(_) => ErrorType::UserError,
+                    Error::Internal(_) => ErrorType::InternalError,
+                };
+
+                sender
+                    .send(Box::new(SyncError::InstanceStartFailed(
+                        err_type,
+                        format!("Failed to start microVM. {:?}", e),
+                    ))).map_err(|_| ())
+                    .expect("one-shot channel closed")
+            }
         };
     }