Detect lost messages

Messages sent to a mailbox that wasn't added to the simulation are now
specifically detected. Earlier this would be wrongly reported as a
deadlock.

nexosim/build.rs

@@ -3,7 +3,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     tonic_build::configure()
         .build_client(false)
         .out_dir("src/grpc/codegen/")
-        .compile(&["simulation.proto"], &["src/grpc/api/"])?;
+        .compile_protos(&["simulation.proto"], &["src/grpc/api/"])?;
 
     Ok(())
 }

nexosim/src/executor.rs

@@ -23,8 +23,8 @@ static NEXT_EXECUTOR_ID: AtomicUsize = AtomicUsize::new(0);
 
 #[derive(Debug)]
 pub(crate) enum ExecutorError {
-    /// The simulation has deadlocked.
+    /// Not all messages have been processed.
-    Deadlock,
+    UnprocessedMessages(usize),
     /// The simulation has timed out.
     Timeout,
     /// The simulation has panicked.

nexosim/src/executor/mt_executor.rs

@@ -250,9 +250,9 @@ impl Executor {
             if self.context.pool_manager.pool_is_idle() {
                 let msg_count = self.context.msg_count.load(Ordering::Relaxed);
                 if msg_count != 0 {
-                    assert!(msg_count > 0);
+                    let msg_count: usize = msg_count.try_into().unwrap();
 
-                    return Err(ExecutorError::Deadlock);
+                    return Err(ExecutorError::UnprocessedMessages(msg_count));
                 }
 
                 return Ok(());

nexosim/src/executor/st_executor.rs

@@ -193,12 +193,12 @@ impl ExecutorInner {
             return Err(ExecutorError::Panic(model_id, payload));
         }
 
-        // Check for deadlock.
+        // Check for unprocessed messages.
         self.context.msg_count = channel::THREAD_MSG_COUNT.replace(msg_count_stash);
         if self.context.msg_count != 0 {
-            assert!(self.context.msg_count > 0);
+            let msg_count: usize = self.context.msg_count.try_into().unwrap();
 
-            return Err(ExecutorError::Deadlock);
+            return Err(ExecutorError::UnprocessedMessages(msg_count));
         }
 
         Ok(())

nexosim/src/grpc/api/simulation.proto

@@ -12,11 +12,12 @@ enum ErrorCode {
   SIMULATION_NOT_STARTED = 1;
   SIMULATION_TERMINATED = 2;
   SIMULATION_DEADLOCK = 3;
-  SIMULATION_PANIC = 4;
+  SIMULATION_MESSAGE_LOSS = 4;
-  SIMULATION_TIMEOUT = 5;
+  SIMULATION_PANIC = 5;
-  SIMULATION_OUT_OF_SYNC = 6;
+  SIMULATION_TIMEOUT = 6;
-  SIMULATION_BAD_QUERY = 7;
+  SIMULATION_OUT_OF_SYNC = 7;
-  SIMULATION_TIME_OUT_OF_RANGE = 8;
+  SIMULATION_BAD_QUERY = 8;
+  SIMULATION_TIME_OUT_OF_RANGE = 9;
   MISSING_ARGUMENT = 20;
   INVALID_TIME = 30;
   INVALID_PERIOD = 31;

nexosim/src/grpc/codegen/simulation.rs

@@ -338,11 +338,12 @@ pub enum ErrorCode {
     SimulationNotStarted = 1,
     SimulationTerminated = 2,
     SimulationDeadlock = 3,
-    SimulationPanic = 4,
+    SimulationMessageLoss = 4,
-    SimulationTimeout = 5,
+    SimulationPanic = 5,
-    SimulationOutOfSync = 6,
+    SimulationTimeout = 6,
-    SimulationBadQuery = 7,
+    SimulationOutOfSync = 7,
-    SimulationTimeOutOfRange = 8,
+    SimulationBadQuery = 8,
+    SimulationTimeOutOfRange = 9,
     MissingArgument = 20,
     InvalidTime = 30,
     InvalidPeriod = 31,
@@ -359,23 +360,24 @@ impl ErrorCode {
     /// (if the ProtoBuf definition does not change) and safe for programmatic use.
     pub fn as_str_name(&self) -> &'static str {
         match self {
-            ErrorCode::InternalError => "INTERNAL_ERROR",
+            Self::InternalError => "INTERNAL_ERROR",
-            ErrorCode::SimulationNotStarted => "SIMULATION_NOT_STARTED",
+            Self::SimulationNotStarted => "SIMULATION_NOT_STARTED",
-            ErrorCode::SimulationTerminated => "SIMULATION_TERMINATED",
+            Self::SimulationTerminated => "SIMULATION_TERMINATED",
-            ErrorCode::SimulationDeadlock => "SIMULATION_DEADLOCK",
+            Self::SimulationDeadlock => "SIMULATION_DEADLOCK",
-            ErrorCode::SimulationPanic => "SIMULATION_PANIC",
+            Self::SimulationMessageLoss => "SIMULATION_MESSAGE_LOSS",
-            ErrorCode::SimulationTimeout => "SIMULATION_TIMEOUT",
+            Self::SimulationPanic => "SIMULATION_PANIC",
-            ErrorCode::SimulationOutOfSync => "SIMULATION_OUT_OF_SYNC",
+            Self::SimulationTimeout => "SIMULATION_TIMEOUT",
-            ErrorCode::SimulationBadQuery => "SIMULATION_BAD_QUERY",
+            Self::SimulationOutOfSync => "SIMULATION_OUT_OF_SYNC",
-            ErrorCode::SimulationTimeOutOfRange => "SIMULATION_TIME_OUT_OF_RANGE",
+            Self::SimulationBadQuery => "SIMULATION_BAD_QUERY",
-            ErrorCode::MissingArgument => "MISSING_ARGUMENT",
+            Self::SimulationTimeOutOfRange => "SIMULATION_TIME_OUT_OF_RANGE",
-            ErrorCode::InvalidTime => "INVALID_TIME",
+            Self::MissingArgument => "MISSING_ARGUMENT",
-            ErrorCode::InvalidPeriod => "INVALID_PERIOD",
+            Self::InvalidTime => "INVALID_TIME",
-            ErrorCode::InvalidDeadline => "INVALID_DEADLINE",
+            Self::InvalidPeriod => "INVALID_PERIOD",
-            ErrorCode::InvalidMessage => "INVALID_MESSAGE",
+            Self::InvalidDeadline => "INVALID_DEADLINE",
-            ErrorCode::InvalidKey => "INVALID_KEY",
+            Self::InvalidMessage => "INVALID_MESSAGE",
-            ErrorCode::SourceNotFound => "SOURCE_NOT_FOUND",
+            Self::InvalidKey => "INVALID_KEY",
-            ErrorCode::SinkNotFound => "SINK_NOT_FOUND",
+            Self::SourceNotFound => "SOURCE_NOT_FOUND",
+            Self::SinkNotFound => "SINK_NOT_FOUND",
         }
     }
     /// Creates an enum from field names used in the ProtoBuf definition.
@@ -385,6 +387,7 @@ impl ErrorCode {
             "SIMULATION_NOT_STARTED" => Some(Self::SimulationNotStarted),
             "SIMULATION_TERMINATED" => Some(Self::SimulationTerminated),
             "SIMULATION_DEADLOCK" => Some(Self::SimulationDeadlock),
+            "SIMULATION_MESSAGE_LOSS" => Some(Self::SimulationMessageLoss),
             "SIMULATION_PANIC" => Some(Self::SimulationPanic),
             "SIMULATION_TIMEOUT" => Some(Self::SimulationTimeout),
             "SIMULATION_OUT_OF_SYNC" => Some(Self::SimulationOutOfSync),
@@ -404,7 +407,13 @@ impl ErrorCode {
 }
 /// Generated server implementations.
 pub mod simulation_server {
-    #![allow(unused_variables, dead_code, missing_docs, clippy::let_unit_value)]
+    #![allow(
+        unused_variables,
+        dead_code,
+        missing_docs,
+        clippy::wildcard_imports,
+        clippy::let_unit_value,
+    )]
     use tonic::codegen::*;
     /// Generated trait containing gRPC methods that should be implemented for use with SimulationServer.
     #[async_trait]
@@ -1033,17 +1042,19 @@ pub mod simulation_server {
                 }
                 _ => {
                     Box::pin(async move {
-                        Ok(
+                        let mut response = http::Response::new(empty_body());
-                            http::Response::builder()
+                        let headers = response.headers_mut();
-                                .status(200)
+                        headers
-                                .header("grpc-status", tonic::Code::Unimplemented as i32)
+                            .insert(
-                                .header(
+                                tonic::Status::GRPC_STATUS,
+                                (tonic::Code::Unimplemented as i32).into(),
+                            );
+                        headers
+                            .insert(
                                 http::header::CONTENT_TYPE,
                                 tonic::metadata::GRPC_CONTENT_TYPE,
-                                )
+                            );
-                                .body(empty_body())
+                        Ok(response)
-                                .unwrap(),
-                        )
                     })
                 }
             }

nexosim/src/grpc/services.rs

@@ -34,6 +34,7 @@ fn simulation_not_started_error() -> Error {
 fn map_execution_error(error: ExecutionError) -> Error {
     let error_code = match error {
         ExecutionError::Deadlock(_) => ErrorCode::SimulationDeadlock,
+        ExecutionError::MessageLoss(_) => ErrorCode::SimulationMessageLoss,
         ExecutionError::Panic { .. } => ErrorCode::SimulationPanic,
         ExecutionError::Timeout => ErrorCode::SimulationTimeout,
         ExecutionError::OutOfSync(_) => ErrorCode::SimulationOutOfSync,

nexosim/src/simulation.rs

@@ -333,7 +333,7 @@ impl Simulation {
         }
 
         self.executor.run(self.timeout).map_err(|e| match e {
-            ExecutorError::Deadlock => {
+            ExecutorError::UnprocessedMessages(msg_count) => {
                 self.is_terminated = true;
                 let mut deadlock_info = Vec::new();
                 for (model, observer) in &self.observers {
@@ -346,8 +346,12 @@ impl Simulation {
                     }
                 }
 
+                if deadlock_info.is_empty() {
+                    ExecutionError::MessageLoss(msg_count)
+                } else {
                     ExecutionError::Deadlock(deadlock_info)
                 }
+            }
             ExecutorError::Timeout => {
                 self.is_terminated = true;
 
@@ -525,14 +529,22 @@ pub struct DeadlockInfo {
 /// An error returned upon simulation execution failure.
 #[derive(Debug)]
 pub enum ExecutionError {
-    /// The simulation has been terminated due to an earlier deadlock, model
+    /// The simulation has been terminated due to an earlier deadlock, message
-    /// panic, timeout or synchronization loss.
+    /// loss, model panic, timeout or synchronization loss.
     Terminated,
     /// The simulation has deadlocked due to the enlisted models.
     ///
     /// This is a fatal error: any subsequent attempt to run the simulation will
     /// return an [`ExecutionError::Terminated`] error.
     Deadlock(Vec<DeadlockInfo>),
+    /// One or more message were left unprocessed because the recipient's
+    /// mailbox was not migrated to the simulation.
+    ///
+    /// The payload indicates the number of lost messages.
+    ///
+    /// This is a fatal error: any subsequent attempt to run the simulation will
+    /// return an [`ExecutionError::Terminated`] error.
+    MessageLoss(usize),
     /// A panic was caught during execution.
     ///
     /// This is a fatal error: any subsequent attempt to run the simulation will
@@ -604,6 +616,9 @@ impl fmt::Display for ExecutionError {
 
                 Ok(())
             }
+            Self::MessageLoss(count) => {
+                write!(f, "{} messages have been lost", count)
+            }
             Self::Panic{model, payload} => {
                 let msg: &str = if let Some(s) = payload.downcast_ref::<&str>() {
                     s

nexosim/tests/integration/main.rs

@@ -5,6 +5,7 @@ mod model_scheduling;
 #[cfg(not(miri))]
 mod simulation_clock_sync;
 mod simulation_deadlock;
+mod simulation_message_loss;
 mod simulation_panic;
 mod simulation_scheduling;
 #[cfg(not(miri))]

nexosim/tests/integration/simulation_message_loss.rs

@@ -0,0 +1,99 @@
+//! Message loss detection.
+
+use nexosim::model::Model;
+use nexosim::ports::{Output, Requestor};
+use nexosim::simulation::{ExecutionError, Mailbox, SimInit};
+use nexosim::time::MonotonicTime;
+
+const MT_NUM_THREADS: usize = 4;
+
+#[derive(Default)]
+struct TestModel {
+    output: Output<()>,
+    requestor: Requestor<(), ()>,
+}
+impl TestModel {
+    async fn activate_output_twice(&mut self) {
+        self.output.send(()).await;
+        self.output.send(()).await;
+    }
+    async fn activate_requestor_twice(&mut self) {
+        let _ = self.requestor.send(()).await;
+        let _ = self.requestor.send(()).await;
+    }
+}
+impl Model for TestModel {}
+
+/// Loose an event.
+fn event_loss(num_threads: usize) {
+    let mut model = TestModel::default();
+    let mbox = Mailbox::new();
+    let addr = mbox.address();
+    let bad_mbox = Mailbox::new();
+
+    // Make two self-connections so that each outgoing message generates two
+    // incoming messages.
+    model
+        .output
+        .connect(TestModel::activate_output_twice, &bad_mbox);
+
+    let t0 = MonotonicTime::EPOCH;
+    let mut simu = SimInit::with_num_threads(num_threads)
+        .add_model(model, mbox, "")
+        .init(t0)
+        .unwrap()
+        .0;
+
+    match simu.process_event(TestModel::activate_output_twice, (), addr) {
+        Err(ExecutionError::MessageLoss(msg_count)) => {
+            assert_eq!(msg_count, 2);
+        }
+        _ => panic!("message loss not detected"),
+    }
+}
+
+/// Loose an event.
+fn request_loss(num_threads: usize) {
+    let mut model = TestModel::default();
+    let mbox = Mailbox::new();
+    let addr = mbox.address();
+    let bad_mbox = Mailbox::new();
+
+    model
+        .requestor
+        .connect(TestModel::activate_requestor_twice, &bad_mbox);
+
+    let t0 = MonotonicTime::EPOCH;
+    let mut simu = SimInit::with_num_threads(num_threads)
+        .add_model(model, mbox, "")
+        .init(t0)
+        .unwrap()
+        .0;
+
+    match simu.process_event(TestModel::activate_requestor_twice, (), addr) {
+        Err(ExecutionError::MessageLoss(msg_count)) => {
+            assert_eq!(msg_count, 1);
+        }
+        _ => panic!("message loss not detected"),
+    }
+}
+
+#[test]
+fn event_loss_st() {
+    event_loss(1);
+}
+
+#[test]
+fn event_loss_mt() {
+    event_loss(MT_NUM_THREADS);
+}
+
+#[test]
+fn request_loss_st() {
+    request_loss(1);
+}
+
+#[test]
+fn request_loss_mt() {
+    request_loss(MT_NUM_THREADS);
+}