fix: Refactor error propagation

Refactors error propagation to avoid logging and printing misleading
error messages.

Signed-off-by: Jonathan Woollett-Light <jcawl@amazon.co.uk>

CHANGELOG.md

@@ -15,6 +15,10 @@
 - Simplified and clarified the removal policy of deprecated API elements
  to follow semantic versioning 2.0.0. For more information, please refer to
  [this GitHub discussion](https://github.com/firecracker-microvm/firecracker/discussions/4135).
+- [#4180](https://github.com/firecracker-microvm/firecracker/pull/4180):
+ Refactored error propagation to avoid logging and printing an error on
+ exits with a zero exit code. Now, on successful exit
+ "Firecracker exited successfully" is logged.
 
 ### Deprecated
 

src/firecracker/src/api_server_adapter.rs

@@ -52,7 +52,7 @@ impl ApiServerAdapter {
  vm_resources: VmResources,
  vmm: Arc<Mutex<Vmm>>,
  event_manager: &mut EventManager,
- ) -> FcExitCode {
+ ) -> Result<(), FcExitCode> {
  let api_adapter = Arc::new(Mutex::new(Self {
  api_event_fd,
  from_api,
@@ -64,10 +64,14 @@ impl ApiServerAdapter {
  event_manager
  .run()
  .expect("EventManager events driver fatal error");
- if let Some(exit_code) = vmm.lock().unwrap().shutdown_exit_code() {
- return exit_code;
+
+ match vmm.lock().unwrap().shutdown_exit_code() {
+ Some(FcExitCode::Ok) => break,
+ Some(exit_code) => return Err(exit_code),
+ None => continue,
  }
  }
+ Ok(())
  }
 
  fn handle_request(&mut self, req_action: VmmAction) {
@@ -245,7 +249,8 @@ pub(crate) fn run_with_api(
  api_thread.join().expect("Api thread should join");
 
  match result {
- Ok(exit_code) => Err(ApiServerError::MicroVMStoppedWithoutError(exit_code)),
+ Ok(Ok(())) => Ok(()),
+ Ok(Err(exit_code)) => Err(ApiServerError::MicroVMStoppedWithoutError(exit_code)),
  Err(exit_error) => Err(exit_error),
  }
 }

src/firecracker/src/main.rs

@@ -98,6 +98,7 @@ fn main() -> ExitCode {
  eprintln!("Error: {err:?}");
  ExitCode::from(err)
  } else {
+ info!("Firecracker exited successfully");
  ExitCode::SUCCESS
  }
 }
@@ -631,8 +632,11 @@ fn run_without_api(
  .run()
  .expect("Failed to start the event manager");
 
- if let Some(exit_code) = vmm.lock().unwrap().shutdown_exit_code() {
- return Err(RunWithoutApiError::Shutdown(exit_code));
+ match vmm.lock().unwrap().shutdown_exit_code() {
+ Some(FcExitCode::Ok) => break,
+ Some(exit_code) => return Err(RunWithoutApiError::Shutdown(exit_code)),
+ None => continue,
  }
  }
+ Ok(())
 }

tests/integration_tests/functional/test_cmd_line_start.py

@@ -170,9 +170,7 @@ def test_config_start_no_api_exit(uvm_plain, vm_config_file):
  time.sleep(3) # Wait for shutdown
 
  # Check error log
- test_microvm.check_log_message(
- "RunWithoutApiError error: MicroVMStopped without an error: Ok"
- )
+ test_microvm.check_log_message("Firecracker exited successfully")
 
 
 @pytest.mark.parametrize(