Initial (g)RPC implementation

asynchronix/src/rpc/api/custom_transport.proto

@@ -0,0 +1,50 @@
+// Additional types for transport implementations which, unlike gRPC, do not
+// support auto-generation from the `Simulation` service description.
+
+syntax = "proto3";
+package custom_transport;
+
+import "simulation.proto";
+
+enum ServerErrorCode {
+  UNKNOWN_REQUEST = 0;
+  EMPTY_REQUEST = 1;
+}
+
+message ServerError {
+  ServerErrorCode code = 1;
+  string message = 2;
+}
+
+message AnyRequest {
+  oneof request { // Expects exactly 1 variant.
+    simulation.InitRequest init_request = 1;
+    simulation.TimeRequest time_request = 2;
+    simulation.StepRequest step_request = 3;
+    simulation.StepUntilRequest step_until_request = 4;
+    simulation.ScheduleEventRequest schedule_event_request = 5;
+    simulation.CancelEventRequest cancel_event_request = 6;
+    simulation.ProcessEventRequest process_event_request = 7;
+    simulation.ProcessQueryRequest process_query_request = 8;
+    simulation.ReadEventsRequest read_events_request = 9;
+    simulation.OpenSinkRequest open_sink_request = 10;
+    simulation.CloseSinkRequest close_sink_request = 11;
+  }
+}
+
+message AnyReply {
+  oneof reply { // Contains exactly 1 variant.
+    simulation.InitReply init_reply = 1;
+    simulation.TimeReply time_reply = 2;
+    simulation.StepReply step_reply = 3;
+    simulation.StepUntilReply step_until_reply = 4;
+    simulation.ScheduleEventReply schedule_event_reply = 5;
+    simulation.CancelEventReply cancel_event_reply = 6;
+    simulation.ProcessEventReply process_event_reply = 7;
+    simulation.ProcessQueryReply process_query_reply = 8;
+    simulation.ReadEventsReply read_events_reply = 9;
+    simulation.OpenSinkReply open_sink_reply = 10;
+    simulation.CloseSinkReply close_sink_reply = 11;
+    ServerError error = 100;
+  }
+}

asynchronix/src/rpc/api/simulation.proto

@@ -0,0 +1,161 @@
+// The main simulation protocol.
+
+syntax = "proto3";
+package simulation;
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/empty.proto";
+
+enum ErrorCode {
+  INTERNAL_ERROR = 0;
+  SIMULATION_NOT_STARTED = 1;
+  MISSING_ARGUMENT = 2;
+  INVALID_TIME = 3;
+  INVALID_DURATION = 4;
+  INVALID_MESSAGE = 5;
+  INVALID_KEY = 6;
+  SOURCE_NOT_FOUND = 10;
+  SINK_NOT_FOUND = 11;
+  KEY_NOT_FOUND = 12;
+  SIMULATION_TIME_OUT_OF_RANGE = 13;
+}
+
+message Error {
+  ErrorCode code = 1;
+  string message = 2;
+}
+
+message EventKey {
+  uint64 subkey1 = 1;
+  uint64 subkey2 = 2;
+}
+
+message InitRequest { optional google.protobuf.Timestamp time = 1; }
+message InitReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 1;
+    Error error = 100;
+  }
+}
+
+message TimeRequest {}
+message TimeReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Timestamp time = 1;
+    Error error = 100;
+  }
+}
+
+message StepRequest {}
+message StepReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Timestamp time = 1;
+    Error error = 100;
+  }
+}
+
+message StepUntilRequest {
+  oneof deadline { // Always returns exactly 1 variant.
+    google.protobuf.Timestamp time = 1;
+    google.protobuf.Duration duration = 2;
+  }
+}
+message StepUntilReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Timestamp time = 1;
+    Error error = 100;
+  }
+}
+
+message ScheduleEventRequest {
+  oneof deadline { // Expects exactly 1 variant.
+    google.protobuf.Timestamp time = 1;
+    google.protobuf.Duration duration = 2;
+  }
+  string source_name = 3;
+  bytes event = 4;
+  optional google.protobuf.Duration period = 5;
+  optional bool with_key = 6;
+}
+message ScheduleEventReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 1;
+    EventKey key = 2;
+    Error error = 100;
+  }
+}
+
+message CancelEventRequest { EventKey key = 1; }
+message CancelEventReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 1;
+    Error error = 100;
+  }
+}
+
+message ProcessEventRequest {
+  string source_name = 1;
+  bytes event = 2;
+}
+message ProcessEventReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 1;
+    Error error = 100;
+  }
+}
+
+message ProcessQueryRequest {
+  string source_name = 1;
+  bytes request = 2;
+}
+message ProcessQueryReply {
+  // This field is hoisted because protobuf3 does not support `repeated` within
+  // a `oneof`. It is Always empty if an error is returned
+  repeated bytes replies = 1;
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 10;
+    Error error = 100;
+  }
+}
+
+message ReadEventsRequest { string sink_name = 1; }
+message ReadEventsReply {
+  // This field is hoisted because protobuf3 does not support `repeated` within
+  // a `oneof`. It is Always empty if an error is returned
+  repeated bytes events = 1;
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 10;
+    Error error = 100;
+  }
+}
+
+message OpenSinkRequest { string sink_name = 1; }
+message OpenSinkReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 10;
+    Error error = 100;
+  }
+}
+
+message CloseSinkRequest { string sink_name = 1; }
+message CloseSinkReply {
+  oneof result { // Always returns exactly 1 variant.
+    google.protobuf.Empty empty = 10;
+    Error error = 100;
+  }
+}
+
+service Simulation {
+  rpc Init(InitRequest) returns (InitReply);
+  rpc Time(TimeRequest) returns (TimeReply);
+  rpc Step(StepRequest) returns (StepReply);
+  rpc StepUntil(StepUntilRequest) returns (StepUntilReply);
+  rpc ScheduleEvent(ScheduleEventRequest) returns (ScheduleEventReply);
+  rpc CancelEvent(CancelEventRequest) returns (CancelEventReply);
+  rpc ProcessEvent(ProcessEventRequest) returns (ProcessEventReply);
+  rpc ProcessQuery(ProcessQueryRequest) returns (ProcessQueryReply);
+  rpc ReadEvents(ReadEventsRequest) returns (ReadEventsReply);
+  rpc OpenSink(OpenSinkRequest) returns (OpenSinkReply);
+  rpc CloseSink(CloseSinkRequest) returns (CloseSinkReply);
+}

asynchronix/src/rpc/codegen.rs

@@ -0,0 +1,5 @@
+#![allow(unreachable_pub)]
+#![allow(clippy::enum_variant_names)]
+
+pub(crate) mod custom_transport;
+pub(crate) mod simulation;

asynchronix/src/rpc/codegen/custom_transport.rs

@@ -0,0 +1,111 @@
+// This file is @generated by prost-build.
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct ServerError {
+    #[prost(enumeration = "ServerErrorCode", tag = "1")]
+    pub code: i32,
+    #[prost(string, tag = "2")]
+    pub message: ::prost::alloc::string::String,
+}
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct AnyRequest {
+    /// Expects exactly 1 variant.
+    #[prost(oneof = "any_request::Request", tags = "1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11")]
+    pub request: ::core::option::Option<any_request::Request>,
+}
+/// Nested message and enum types in `AnyRequest`.
+pub mod any_request {
+    /// Expects exactly 1 variant.
+    #[allow(clippy::derive_partial_eq_without_eq)]
+    #[derive(Clone, PartialEq, ::prost::Oneof)]
+    pub enum Request {
+        #[prost(message, tag = "1")]
+        InitRequest(super::super::simulation::InitRequest),
+        #[prost(message, tag = "2")]
+        TimeRequest(super::super::simulation::TimeRequest),
+        #[prost(message, tag = "3")]
+        StepRequest(super::super::simulation::StepRequest),
+        #[prost(message, tag = "4")]
+        StepUntilRequest(super::super::simulation::StepUntilRequest),
+        #[prost(message, tag = "5")]
+        ScheduleEventRequest(super::super::simulation::ScheduleEventRequest),
+        #[prost(message, tag = "6")]
+        CancelEventRequest(super::super::simulation::CancelEventRequest),
+        #[prost(message, tag = "7")]
+        ProcessEventRequest(super::super::simulation::ProcessEventRequest),
+        #[prost(message, tag = "8")]
+        ProcessQueryRequest(super::super::simulation::ProcessQueryRequest),
+        #[prost(message, tag = "9")]
+        ReadEventsRequest(super::super::simulation::ReadEventsRequest),
+        #[prost(message, tag = "10")]
+        OpenSinkRequest(super::super::simulation::OpenSinkRequest),
+        #[prost(message, tag = "11")]
+        CloseSinkRequest(super::super::simulation::CloseSinkRequest),
+    }
+}
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct AnyReply {
+    /// Contains exactly 1 variant.
+    #[prost(oneof = "any_reply::Reply", tags = "1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 100")]
+    pub reply: ::core::option::Option<any_reply::Reply>,
+}
+/// Nested message and enum types in `AnyReply`.
+pub mod any_reply {
+    /// Contains exactly 1 variant.
+    #[allow(clippy::derive_partial_eq_without_eq)]
+    #[derive(Clone, PartialEq, ::prost::Oneof)]
+    pub enum Reply {
+        #[prost(message, tag = "1")]
+        InitReply(super::super::simulation::InitReply),
+        #[prost(message, tag = "2")]
+        TimeReply(super::super::simulation::TimeReply),
+        #[prost(message, tag = "3")]
+        StepReply(super::super::simulation::StepReply),
+        #[prost(message, tag = "4")]
+        StepUntilReply(super::super::simulation::StepUntilReply),
+        #[prost(message, tag = "5")]
+        ScheduleEventReply(super::super::simulation::ScheduleEventReply),
+        #[prost(message, tag = "6")]
+        CancelEventReply(super::super::simulation::CancelEventReply),
+        #[prost(message, tag = "7")]
+        ProcessEventReply(super::super::simulation::ProcessEventReply),
+        #[prost(message, tag = "8")]
+        ProcessQueryReply(super::super::simulation::ProcessQueryReply),
+        #[prost(message, tag = "9")]
+        ReadEventsReply(super::super::simulation::ReadEventsReply),
+        #[prost(message, tag = "10")]
+        OpenSinkReply(super::super::simulation::OpenSinkReply),
+        #[prost(message, tag = "11")]
+        CloseSinkReply(super::super::simulation::CloseSinkReply),
+        #[prost(message, tag = "100")]
+        Error(super::ServerError),
+    }
+}
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
+#[repr(i32)]
+pub enum ServerErrorCode {
+    UnknownRequest = 0,
+    EmptyRequest = 1,
+}
+impl ServerErrorCode {
+    /// String value of the enum field names used in the ProtoBuf definition.
+    ///
+    /// The values are not transformed in any way and thus are considered stable
+    /// (if the ProtoBuf definition does not change) and safe for programmatic use.
+    pub fn as_str_name(&self) -> &'static str {
+        match self {
+            ServerErrorCode::UnknownRequest => "UNKNOWN_REQUEST",
+            ServerErrorCode::EmptyRequest => "EMPTY_REQUEST",
+        }
+    }
+    /// Creates an enum from field names used in the ProtoBuf definition.
+    pub fn from_str_name(value: &str) -> ::core::option::Option<Self> {
+        match value {
+            "UNKNOWN_REQUEST" => Some(Self::UnknownRequest),
+            "EMPTY_REQUEST" => Some(Self::EmptyRequest),
+            _ => None,
+        }
+    }
+}

asynchronix/src/rpc/endpoint_registry.rs

@@ -0,0 +1,307 @@
+use std::collections::hash_map::Entry;
+use std::collections::HashMap;
+use std::fmt;
+use std::time::Duration;
+
+use rmp_serde::decode::Error as RmpDecodeError;
+use rmp_serde::encode::Error as RmpEncodeError;
+use serde::de::DeserializeOwned;
+use serde::Serialize;
+
+use crate::ports::{EventSinkStream, EventSource, QuerySource, ReplyReceiver};
+use crate::time::{Action, ActionKey};
+
+/// A registry that holds all sources and sinks meant to be accessed through
+/// remote procedure calls.
+#[derive(Default)]
+pub struct EndpointRegistry {
+    event_sources: HashMap<String, Box<dyn EventSourceAny>>,
+    query_sources: HashMap<String, Box<dyn QuerySourceAny>>,
+    sinks: HashMap<String, Box<dyn EventSinkStreamAny>>,
+}
+
+impl EndpointRegistry {
+    /// Creates an empty `EndpointRegistry`.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Adds an event source to the registry.
+    ///
+    /// If the specified name is already in use for another event source, the source
+    /// provided as argument is returned in the error.
+    pub fn add_event_source<T>(
+        &mut self,
+        source: EventSource<T>,
+        name: impl Into<String>,
+    ) -> Result<(), EventSource<T>>
+    where
+        T: DeserializeOwned + Clone + Send + 'static,
+    {
+        match self.event_sources.entry(name.into()) {
+            Entry::Vacant(s) => {
+                s.insert(Box::new(source));
+
+                Ok(())
+            }
+            Entry::Occupied(_) => Err(source),
+        }
+    }
+
+    /// Returns a mutable reference to the specified event source if it is in
+    /// the registry.
+    pub(crate) fn get_event_source_mut(&mut self, name: &str) -> Option<&mut dyn EventSourceAny> {
+        self.event_sources.get_mut(name).map(|s| s.as_mut())
+    }
+
+    /// Adds an query source to the registry.
+    ///
+    /// If the specified name is already in use for another query source, the source
+    /// provided as argument is returned in the error.
+    pub fn add_query_source<T, R>(
+        &mut self,
+        source: QuerySource<T, R>,
+        name: impl Into<String>,
+    ) -> Result<(), QuerySource<T, R>>
+    where
+        T: DeserializeOwned + Clone + Send + 'static,
+        R: Serialize + Send + 'static,
+    {
+        match self.query_sources.entry(name.into()) {
+            Entry::Vacant(s) => {
+                s.insert(Box::new(source));
+
+                Ok(())
+            }
+            Entry::Occupied(_) => Err(source),
+        }
+    }
+
+    /// Returns a mutable reference to the specified query source if it is in
+    /// the registry.
+    pub(crate) fn get_query_source_mut(&mut self, name: &str) -> Option<&mut dyn QuerySourceAny> {
+        self.query_sources.get_mut(name).map(|s| s.as_mut())
+    }
+
+    /// Adds a sink to the registry.
+    ///
+    /// If the specified name is already in use for another sink, the sink
+    /// provided as argument is returned in the error.
+    pub fn add_sink<S>(&mut self, sink: S, name: impl Into<String>) -> Result<(), S>
+    where
+        S: EventSinkStream + Send + 'static,
+        S::Item: Serialize,
+    {
+        match self.sinks.entry(name.into()) {
+            Entry::Vacant(s) => {
+                s.insert(Box::new(sink));
+
+                Ok(())
+            }
+            Entry::Occupied(_) => Err(sink),
+        }
+    }
+
+    /// Returns a mutable reference to the specified sink if it is in the
+    /// registry.
+    pub(crate) fn get_sink_mut(&mut self, name: &str) -> Option<&mut dyn EventSinkStreamAny> {
+        self.sinks.get_mut(name).map(|s| s.as_mut())
+    }
+}
+
+impl fmt::Debug for EndpointRegistry {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "EndpointRegistry ({} sources, {} sinks)",
+            self.event_sources.len(),
+            self.sinks.len()
+        )
+    }
+}
+
+/// A type-erased `EventSource` that operates on MessagePack-encoded serialized
+/// events.
+pub(crate) trait EventSourceAny: Send + 'static {
+    /// Returns an action which, when processed, broadcasts an event to all
+    /// connected input ports.
+    ///
+    /// The argument is expected to conform to the serde MessagePack encoding.
+    fn event(&mut self, msgpack_arg: &[u8]) -> Result<Action, RmpDecodeError>;
+
+    /// Returns a cancellable action and a cancellation key; when processed, the
+    /// action broadcasts an event to all connected input ports.
+    ///
+    /// The argument is expected to conform to the serde MessagePack encoding.
+    fn keyed_event(&mut self, msgpack_arg: &[u8]) -> Result<(Action, ActionKey), RmpDecodeError>;
+
+    /// Returns a periodically recurring action which, when processed,
+    /// broadcasts an event to all connected input ports.
+    ///
+    /// The argument is expected to conform to the serde MessagePack encoding.
+    fn periodic_event(
+        &mut self,
+        period: Duration,
+        msgpack_arg: &[u8],
+    ) -> Result<Action, RmpDecodeError>;
+
+    /// Returns a cancellable, periodically recurring action and a cancellation
+    /// key; when processed, the action broadcasts an event to all connected
+    /// input ports.
+    ///
+    /// The argument is expected to conform to the serde MessagePack encoding.
+    fn keyed_periodic_event(
+        &mut self,
+        period: Duration,
+        msgpack_arg: &[u8],
+    ) -> Result<(Action, ActionKey), RmpDecodeError>;
+
+    /// Human-readable name of the event type, as returned by
+    /// `any::type_name()`.
+    fn event_type_name(&self) -> &'static str;
+}
+
+impl<T> EventSourceAny for EventSource<T>
+where
+    T: DeserializeOwned + Clone + Send + 'static,
+{
+    fn event(&mut self, msgpack_arg: &[u8]) -> Result<Action, RmpDecodeError> {
+        rmp_serde::from_read(msgpack_arg).map(|arg| self.event(arg))
+    }
+    fn keyed_event(&mut self, msgpack_arg: &[u8]) -> Result<(Action, ActionKey), RmpDecodeError> {
+        rmp_serde::from_read(msgpack_arg).map(|arg| self.keyed_event(arg))
+    }
+    fn periodic_event(
+        &mut self,
+        period: Duration,
+        msgpack_arg: &[u8],
+    ) -> Result<Action, RmpDecodeError> {
+        rmp_serde::from_read(msgpack_arg).map(|arg| self.periodic_event(period, arg))
+    }
+    fn keyed_periodic_event(
+        &mut self,
+        period: Duration,
+        msgpack_arg: &[u8],
+    ) -> Result<(Action, ActionKey), RmpDecodeError> {
+        rmp_serde::from_read(msgpack_arg).map(|arg| self.keyed_periodic_event(period, arg))
+    }
+    fn event_type_name(&self) -> &'static str {
+        std::any::type_name::<T>()
+    }
+}
+
+/// A type-erased `QuerySource` that operates on MessagePack-encoded serialized
+/// queries and returns MessagePack-encoded replies.
+pub(crate) trait QuerySourceAny: Send + 'static {
+    /// Returns an action which, when processed, broadcasts a query to all
+    /// connected replier ports.
+    ///
+    ///
+    /// The argument is expected to conform to the serde MessagePack encoding.
+    fn query(
+        &mut self,
+        msgpack_arg: &[u8],
+    ) -> Result<(Action, Box<dyn ReplyReceiverAny>), RmpDecodeError>;
+
+    /// Human-readable name of the request type, as returned by
+    /// `any::type_name()`.
+    fn request_type_name(&self) -> &'static str;
+
+    /// Human-readable name of the reply type, as returned by
+    /// `any::type_name()`.
+    fn reply_type_name(&self) -> &'static str;
+}
+
+impl<T, R> QuerySourceAny for QuerySource<T, R>
+where
+    T: DeserializeOwned + Clone + Send + 'static,
+    R: Serialize + Send + 'static,
+{
+    fn query(
+        &mut self,
+        msgpack_arg: &[u8],
+    ) -> Result<(Action, Box<dyn ReplyReceiverAny>), RmpDecodeError> {
+        rmp_serde::from_read(msgpack_arg).map(|arg| {
+            let (action, reply_recv) = self.query(arg);
+            let reply_recv: Box<dyn ReplyReceiverAny> = Box::new(reply_recv);
+
+            (action, reply_recv)
+        })
+    }
+
+    fn request_type_name(&self) -> &'static str {
+        std::any::type_name::<T>()
+    }
+
+    fn reply_type_name(&self) -> &'static str {
+        std::any::type_name::<R>()
+    }
+}
+
+/// A type-erased `EventSinkStream`.
+pub(crate) trait EventSinkStreamAny: Send + 'static {
+    /// Human-readable name of the event type, as returned by
+    /// `any::type_name()`.
+    fn event_type_name(&self) -> &'static str;
+
+    /// Starts or resumes the collection of new events.
+    fn open(&mut self);
+
+    /// Pauses the collection of new events.
+    fn close(&mut self);
+
+    /// Encode and collect all events in a vector.
+    fn collect(&mut self) -> Result<Vec<Vec<u8>>, RmpEncodeError>;
+}
+
+impl<E> EventSinkStreamAny for E
+where
+    E: EventSinkStream + Send + 'static,
+    E::Item: Serialize,
+{
+    fn event_type_name(&self) -> &'static str {
+        std::any::type_name::<E::Item>()
+    }
+
+    fn open(&mut self) {
+        self.open();
+    }
+
+    fn close(&mut self) {
+        self.close();
+    }
+
+    fn collect(&mut self) -> Result<Vec<Vec<u8>>, RmpEncodeError> {
+        EventSinkStream::try_fold(self, Vec::new(), |mut encoded_events, event| {
+            rmp_serde::to_vec_named(&event).map(|encoded_event| {
+                encoded_events.push(encoded_event);
+
+                encoded_events
+            })
+        })
+    }
+}
+
+/// A type-erased `ReplyReceiver` that returns MessagePack-encoded replies..
+pub(crate) trait ReplyReceiverAny {
+    /// Take the replies, if any, encode them and collect them in a vector.
+    fn take_collect(&mut self) -> Option<Result<Vec<Vec<u8>>, RmpEncodeError>>;
+}
+
+impl<R: Serialize + 'static> ReplyReceiverAny for ReplyReceiver<R> {
+    fn take_collect(&mut self) -> Option<Result<Vec<Vec<u8>>, RmpEncodeError>> {
+        let replies = self.take()?;
+
+        let encoded_replies = (move || {
+            let mut encoded_replies = Vec::new();
+            for reply in replies {
+                let encoded_reply = rmp_serde::to_vec_named(&reply)?;
+                encoded_replies.push(encoded_reply);
+            }
+
+            Ok(encoded_replies)
+        })();
+
+        Some(encoded_replies)
+    }
+}

asynchronix/src/rpc/generic_server.rs

@@ -0,0 +1,673 @@
+use std::time::Duration;
+
+use bytes::Buf;
+use prost::Message;
+use prost_types::Timestamp;
+use tai_time::MonotonicTime;
+
+use crate::rpc::key_registry::{KeyRegistry, KeyRegistryId};
+use crate::rpc::EndpointRegistry;
+use crate::simulation::{SimInit, Simulation};
+
+use super::codegen::custom_transport::*;
+use super::codegen::simulation::*;
+
+/// Transport-independent server implementation.
+///
+/// This implementation implements the protobuf services without any
+/// transport-specific management.
+pub(crate) struct GenericServer<F> {
+    sim_gen: F,
+    sim_context: Option<(Simulation, EndpointRegistry, KeyRegistry)>,
+}
+
+impl<F> GenericServer<F>
+where
+    F: FnMut() -> (SimInit, EndpointRegistry) + Send + 'static,
+{
+    /// Creates a new `GenericServer` without any active simulation.
+    pub(crate) fn new(sim_gen: F) -> Self {
+        Self {
+            sim_gen,
+            sim_context: None,
+        }
+    }
+
+    /// Processes an encoded `AnyRequest` message and returns an encoded
+    /// `AnyReply`.
+    #[allow(dead_code)]
+    pub(crate) fn service_request<B>(&mut self, request_buf: B) -> Vec<u8>
+    where
+        B: Buf,
+    {
+        let reply = match AnyRequest::decode(request_buf) {
+            Ok(AnyRequest { request: Some(req) }) => match req {
+                any_request::Request::InitRequest(request) => {
+                    any_reply::Reply::InitReply(self.init(request))
+                }
+                any_request::Request::TimeRequest(request) => {
+                    any_reply::Reply::TimeReply(self.time(request))
+                }
+                any_request::Request::StepRequest(request) => {
+                    any_reply::Reply::StepReply(self.step(request))
+                }
+                any_request::Request::StepUntilRequest(request) => {
+                    any_reply::Reply::StepUntilReply(self.step_until(request))
+                }
+                any_request::Request::ScheduleEventRequest(request) => {
+                    any_reply::Reply::ScheduleEventReply(self.schedule_event(request))
+                }
+                any_request::Request::CancelEventRequest(request) => {
+                    any_reply::Reply::CancelEventReply(self.cancel_event(request))
+                }
+                any_request::Request::ProcessEventRequest(request) => {
+                    any_reply::Reply::ProcessEventReply(self.process_event(request))
+                }
+                any_request::Request::ProcessQueryRequest(request) => {
+                    any_reply::Reply::ProcessQueryReply(self.process_query(request))
+                }
+                any_request::Request::ReadEventsRequest(request) => {
+                    any_reply::Reply::ReadEventsReply(self.read_events(request))
+                }
+                any_request::Request::OpenSinkRequest(request) => {
+                    any_reply::Reply::OpenSinkReply(self.open_sink(request))
+                }
+                any_request::Request::CloseSinkRequest(request) => {
+                    any_reply::Reply::CloseSinkReply(self.close_sink(request))
+                }
+            },
+            Ok(AnyRequest { request: None }) => any_reply::Reply::Error(ServerError {
+                code: ServerErrorCode::EmptyRequest as i32,
+                message: "the message did not contain any request".to_string(),
+            }),
+            Err(err) => any_reply::Reply::Error(ServerError {
+                code: ServerErrorCode::UnknownRequest as i32,
+                message: format!("bad request: {}", err),
+            }),
+        };
+
+        let reply = AnyReply { reply: Some(reply) };
+
+        reply.encode_to_vec()
+    }
+
+    /// Initialize a simulation with the provided time.
+    ///
+    /// If a simulation is already active, it is destructed and replaced with a
+    /// new simulation.
+    ///
+    /// If the initialization time is not provided, it is initialized with the
+    /// epoch of `MonotonicTime` (1970-01-01 00:00:00 TAI).
+    pub(crate) fn init(&mut self, request: InitRequest) -> InitReply {
+        let start_time = request.time.unwrap_or_default();
+        let reply = if let Some(start_time) = timestamp_to_monotonic(start_time) {
+            let (sim_init, endpoint_registry) = (self.sim_gen)();
+            let simulation = sim_init.init(start_time);
+            self.sim_context = Some((simulation, endpoint_registry, KeyRegistry::default()));
+
+            init_reply::Result::Empty(())
+        } else {
+            init_reply::Result::Error(Error {
+                code: ErrorCode::InvalidTime as i32,
+                message: "out-of-range nanosecond field".to_string(),
+            })
+        };
+
+        InitReply {
+            result: Some(reply),
+        }
+    }
+
+    /// Returns the current simulation time.
+    pub(crate) fn time(&mut self, _request: TimeRequest) -> TimeReply {
+        let reply = match &self.sim_context {
+            Some((simulation, ..)) => {
+                if let Some(timestamp) = monotonic_to_timestamp(simulation.time()) {
+                    time_reply::Result::Time(timestamp)
+                } else {
+                    time_reply::Result::Error(Error {
+                        code: ErrorCode::SimulationTimeOutOfRange as i32,
+                        message: "the final simulation time is out of range".to_string(),
+                    })
+                }
+            }
+            None => time_reply::Result::Error(Error {
+                code: ErrorCode::SimulationNotStarted as i32,
+                message: "the simulation was not started".to_string(),
+            }),
+        };
+
+        TimeReply {
+            result: Some(reply),
+        }
+    }
+
+    /// Advances simulation time to that of the next scheduled event, processing
+    /// that event as well as all other event scheduled for the same time.
+    ///
+    /// Processing is gated by a (possibly blocking) call to
+    /// [`Clock::synchronize()`](crate::time::Clock::synchronize) on the
+    /// configured simulation clock. This method blocks until all newly
+    /// processed events have completed.
+    pub(crate) fn step(&mut self, _request: StepRequest) -> StepReply {
+        let reply = match &mut self.sim_context {
+            Some((simulation, ..)) => {
+                simulation.step();
+                if let Some(timestamp) = monotonic_to_timestamp(simulation.time()) {
+                    step_reply::Result::Time(timestamp)
+                } else {
+                    step_reply::Result::Error(Error {
+                        code: ErrorCode::SimulationTimeOutOfRange as i32,
+                        message: "the final simulation time is out of range".to_string(),
+                    })
+                }
+            }
+            None => step_reply::Result::Error(Error {
+                code: ErrorCode::SimulationNotStarted as i32,
+                message: "the simulation was not started".to_string(),
+            }),
+        };
+
+        StepReply {
+            result: Some(reply),
+        }
+    }
+
+    /// Iteratively advances the simulation time until the specified deadline,
+    /// as if by calling
+    /// [`Simulation::step()`](crate::simulation::Simulation::step) repeatedly.
+    ///
+    /// This method blocks until all events scheduled up to the specified target
+    /// time have completed. The simulation time upon completion is equal to the
+    /// specified target time, whether or not an event was scheduled for that
+    /// time.
+    pub(crate) fn step_until(&mut self, request: StepUntilRequest) -> StepUntilReply {
+        let reply = move || -> Result<Timestamp, (ErrorCode, &str)> {
+            let deadline = request
+                .deadline
+                .ok_or((ErrorCode::MissingArgument, "missing deadline argument"))?;
+
+            let simulation = match deadline {
+                step_until_request::Deadline::Time(time) => {
+                    let time = timestamp_to_monotonic(time)
+                        .ok_or((ErrorCode::InvalidTime, "out-of-range nanosecond field"))?;
+
+                    let (simulation, ..) = self.sim_context.as_mut().ok_or((
+                        ErrorCode::SimulationNotStarted,
+                        "the simulation was not started",
+                    ))?;
+
+                    simulation.step_until(time).map_err(|_| {
+                        (
+                            ErrorCode::InvalidTime,
+                            "the specified deadline lies in the past",
+                        )
+                    })?;
+
+                    simulation
+                }
+
+                step_until_request::Deadline::Duration(duration) => {
+                    let duration = to_positive_duration(duration).ok_or((
+                        ErrorCode::InvalidDuration,
+                        "the specified deadline lies in the past",
+                    ))?;
+
+                    let (simulation, ..) = self.sim_context.as_mut().ok_or((
+                        ErrorCode::SimulationNotStarted,
+                        "the simulation was not started",
+                    ))?;
+
+                    simulation.step_by(duration);
+
+                    simulation
+                }
+            };
+
+            let timestamp = monotonic_to_timestamp(simulation.time()).ok_or((
+                ErrorCode::SimulationTimeOutOfRange,
+                "the final simulation time is out of range",
+            ))?;
+
+            Ok(timestamp)
+        }();
+
+        StepUntilReply {
+            result: Some(match reply {
+                Ok(timestamp) => step_until_reply::Result::Time(timestamp),
+                Err((code, message)) => step_until_reply::Result::Error(Error {
+                    code: code as i32,
+                    message: message.to_string(),
+                }),
+            }),
+        }
+    }
+
+    /// Schedules an event at a future time.
+    pub(crate) fn schedule_event(&mut self, request: ScheduleEventRequest) -> ScheduleEventReply {
+        let reply = move || -> Result<Option<KeyRegistryId>, (ErrorCode, String)> {
+            let source_name = &request.source_name;
+            let msgpack_event = &request.event;
+            let with_key = request.with_key.unwrap_or_default();
+            let period = request
+                .period
+                .map(|period| {
+                    to_strictly_positive_duration(period).ok_or((
+                        ErrorCode::InvalidDuration,
+                        "the specified event period is not strictly positive".to_string(),
+                    ))
+                })
+                .transpose()?;
+
+            let (simulation, endpoint_registry, key_registry) =
+                self.sim_context.as_mut().ok_or((
+                    ErrorCode::SimulationNotStarted,
+                    "the simulation was not started".to_string(),
+                ))?;
+
+            let deadline = request.deadline.ok_or((
+                ErrorCode::MissingArgument,
+                "missing deadline argument".to_string(),
+            ))?;
+
+            let deadline = match deadline {
+                schedule_event_request::Deadline::Time(time) => timestamp_to_monotonic(time)
+                    .ok_or((
+                        ErrorCode::InvalidTime,
+                        "out-of-range nanosecond field".to_string(),
+                    ))?,
+                schedule_event_request::Deadline::Duration(duration) => {
+                    let duration = to_strictly_positive_duration(duration).ok_or((
+                        ErrorCode::InvalidDuration,
+                        "the specified scheduling deadline is not in the future".to_string(),
+                    ))?;
+
+                    simulation.time() + duration
+                }
+            };
+
+            let source = endpoint_registry.get_event_source_mut(source_name).ok_or((
+                ErrorCode::SourceNotFound,
+                "no event source is registered with the name '{}'".to_string(),
+            ))?;
+
+            let (action, action_key) = match (with_key, period) {
+                (false, None) => source.event(msgpack_event).map(|action| (action, None)),
+                (false, Some(period)) => source
+                    .periodic_event(period, msgpack_event)
+                    .map(|action| (action, None)),
+                (true, None) => source
+                    .keyed_event(msgpack_event)
+                    .map(|(action, key)| (action, Some(key))),
+                (true, Some(period)) => source
+                    .keyed_periodic_event(period, msgpack_event)
+                    .map(|(action, key)| (action, Some(key))),
+            }
+            .map_err(|_| {
+                (
+                    ErrorCode::InvalidMessage,
+                    format!(
+                        "the event could not be deserialized as type '{}'",
+                        source.event_type_name()
+                    ),
+                )
+            })?;
+
+            let key_id = action_key.map(|action_key| {
+                // Free stale keys from the registry.
+                key_registry.remove_expired_keys(simulation.time());
+
+                if period.is_some() {
+                    key_registry.insert_eternal_key(action_key)
+                } else {
+                    key_registry.insert_key(action_key, deadline)
+                }
+            });
+
+            simulation.process(action);
+
+            Ok(key_id)
+        }();
+
+        ScheduleEventReply {
+            result: Some(match reply {
+                Ok(Some(key_id)) => {
+                    let (subkey1, subkey2) = key_id.into_raw_parts();
+                    schedule_event_reply::Result::Key(EventKey {
+                        subkey1: subkey1
+                            .try_into()
+                            .expect("action key index is too large to be serialized"),
+                        subkey2,
+                    })
+                }
+                Ok(None) => schedule_event_reply::Result::Empty(()),
+                Err((code, message)) => schedule_event_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                }),
+            }),
+        }
+    }
+
+    /// Cancels a keyed event.
+    pub(crate) fn cancel_event(&mut self, request: CancelEventRequest) -> CancelEventReply {
+        let reply = move || -> Result<(), (ErrorCode, String)> {
+            let key = request.key.ok_or((
+                ErrorCode::MissingArgument,
+                "missing key argument".to_string(),
+            ))?;
+            let subkey1: usize = key
+                .subkey1
+                .try_into()
+                .map_err(|_| (ErrorCode::InvalidKey, "invalid event key".to_string()))?;
+            let subkey2 = key.subkey2;
+
+            let (simulation, _, key_registry) = self.sim_context.as_mut().ok_or((
+                ErrorCode::SimulationNotStarted,
+                "the simulation was not started".to_string(),
+            ))?;
+
+            let key_id = KeyRegistryId::from_raw_parts(subkey1, subkey2);
+
+            key_registry.remove_expired_keys(simulation.time());
+            let key = key_registry.extract_key(key_id).ok_or((
+                ErrorCode::InvalidKey,
+                "invalid or expired event key".to_string(),
+            ))?;
+
+            key.cancel();
+
+            Ok(())
+        }();
+
+        CancelEventReply {
+            result: Some(match reply {
+                Ok(()) => cancel_event_reply::Result::Empty(()),
+                Err((code, message)) => cancel_event_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                }),
+            }),
+        }
+    }
+
+    /// Broadcasts an event from an event source immediately, blocking until
+    /// completion.
+    ///
+    /// Simulation time remains unchanged.
+    pub(crate) fn process_event(&mut self, request: ProcessEventRequest) -> ProcessEventReply {
+        let reply = move || -> Result<(), (ErrorCode, String)> {
+            let source_name = &request.source_name;
+            let msgpack_event = &request.event;
+
+            let (simulation, registry, _) = self.sim_context.as_mut().ok_or((
+                ErrorCode::SimulationNotStarted,
+                "the simulation was not started".to_string(),
+            ))?;
+
+            let source = registry.get_event_source_mut(source_name).ok_or((
+                ErrorCode::SourceNotFound,
+                "no source is registered with the name '{}'".to_string(),
+            ))?;
+
+            let event = source.event(msgpack_event).map_err(|_| {
+                (
+                    ErrorCode::InvalidMessage,
+                    format!(
+                        "the event could not be deserialized as type '{}'",
+                        source.event_type_name()
+                    ),
+                )
+            })?;
+
+            simulation.process(event);
+
+            Ok(())
+        }();
+
+        ProcessEventReply {
+            result: Some(match reply {
+                Ok(()) => process_event_reply::Result::Empty(()),
+                Err((code, message)) => process_event_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                }),
+            }),
+        }
+    }
+
+    /// Broadcasts an event from an event source immediately, blocking until
+    /// completion.
+    ///
+    /// Simulation time remains unchanged.
+    pub(crate) fn process_query(&mut self, request: ProcessQueryRequest) -> ProcessQueryReply {
+        let reply = move || -> Result<Vec<Vec<u8>>, (ErrorCode, String)> {
+            let source_name = &request.source_name;
+            let msgpack_request = &request.request;
+
+            let (simulation, registry, _) = self.sim_context.as_mut().ok_or((
+                ErrorCode::SimulationNotStarted,
+                "the simulation was not started".to_string(),
+            ))?;
+
+            let source = registry.get_query_source_mut(source_name).ok_or((
+                ErrorCode::SourceNotFound,
+                "no source is registered with the name '{}'".to_string(),
+            ))?;
+
+            let (query, mut promise) = source.query(msgpack_request).map_err(|_| {
+                (
+                    ErrorCode::InvalidMessage,
+                    format!(
+                        "the request could not be deserialized as type '{}'",
+                        source.request_type_name()
+                    ),
+                )
+            })?;
+
+            simulation.process(query);
+
+            let replies = promise.take_collect().ok_or((
+                ErrorCode::InternalError,
+                "a reply to the query was expected but none was available".to_string(),
+            ))?;
+
+            replies.map_err(|_| {
+                (
+                    ErrorCode::InvalidMessage,
+                    format!(
+                        "the reply could not be serialized as type '{}'",
+                        source.reply_type_name()
+                    ),
+                )
+            })
+        }();
+
+        match reply {
+            Ok(replies) => ProcessQueryReply {
+                replies,
+                result: Some(process_query_reply::Result::Empty(())),
+            },
+            Err((code, message)) => ProcessQueryReply {
+                replies: Vec::new(),
+                result: Some(process_query_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                })),
+            },
+        }
+    }
+
+    /// Read all events from an event sink.
+    pub(crate) fn read_events(&mut self, request: ReadEventsRequest) -> ReadEventsReply {
+        let reply = move || -> Result<Vec<Vec<u8>>, (ErrorCode, String)> {
+            let sink_name = &request.sink_name;
+
+            let (_, registry, _) = self.sim_context.as_mut().ok_or((
+                ErrorCode::SimulationNotStarted,
+                "the simulation was not started".to_string(),
+            ))?;
+
+            let sink = registry.get_sink_mut(sink_name).ok_or((
+                ErrorCode::SinkNotFound,
+                "no sink is registered with the name '{}'".to_string(),
+            ))?;
+
+            sink.collect().map_err(|_| {
+                (
+                    ErrorCode::InvalidMessage,
+                    format!(
+                        "the event could not be serialized from type '{}'",
+                        sink.event_type_name()
+                    ),
+                )
+            })
+        }();
+
+        match reply {
+            Ok(events) => ReadEventsReply {
+                events,
+                result: Some(read_events_reply::Result::Empty(())),
+            },
+            Err((code, message)) => ReadEventsReply {
+                events: Vec::new(),
+                result: Some(read_events_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                })),
+            },
+        }
+    }
+
+    /// Opens an event sink.
+    pub(crate) fn open_sink(&mut self, request: OpenSinkRequest) -> OpenSinkReply {
+        let reply = move || -> Result<(), (ErrorCode, String)> {
+            let sink_name = &request.sink_name;
+
+            let (_, registry, _) = self.sim_context.as_mut().ok_or((
+                ErrorCode::SimulationNotStarted,
+                "the simulation was not started".to_string(),
+            ))?;
+
+            let sink = registry.get_sink_mut(sink_name).ok_or((
+                ErrorCode::SinkNotFound,
+                "no sink is registered with the name '{}'".to_string(),
+            ))?;
+
+            sink.open();
+
+            Ok(())
+        }();
+
+        match reply {
+            Ok(()) => OpenSinkReply {
+                result: Some(open_sink_reply::Result::Empty(())),
+            },
+            Err((code, message)) => OpenSinkReply {
+                result: Some(open_sink_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                })),
+            },
+        }
+    }
+
+    /// Closes an event sink.
+    pub(crate) fn close_sink(&mut self, request: CloseSinkRequest) -> CloseSinkReply {
+        let reply = move || -> Result<(), (ErrorCode, String)> {
+            let sink_name = &request.sink_name;
+
+            let (_, registry, _) = self.sim_context.as_mut().ok_or((
+                ErrorCode::SimulationNotStarted,
+                "the simulation was not started".to_string(),
+            ))?;
+
+            let sink = registry.get_sink_mut(sink_name).ok_or((
+                ErrorCode::SinkNotFound,
+                "no sink is registered with the name '{}'".to_string(),
+            ))?;
+
+            sink.close();
+
+            Ok(())
+        }();
+
+        match reply {
+            Ok(()) => CloseSinkReply {
+                result: Some(close_sink_reply::Result::Empty(())),
+            },
+            Err((code, message)) => CloseSinkReply {
+                result: Some(close_sink_reply::Result::Error(Error {
+                    code: code as i32,
+                    message,
+                })),
+            },
+        }
+    }
+}
+
+/// Attempts a cast from a `MonotonicTime` to a protobuf `Timestamp`.
+///
+/// This will fail if the time is outside the protobuf-specified range for
+/// timestamps (0001-01-01 00:00:00 to 9999-12-31 23:59:59).
+fn monotonic_to_timestamp(monotonic_time: MonotonicTime) -> Option<Timestamp> {
+    // Unix timestamp for 0001-01-01 00:00:00, the minimum accepted by
+    // protobuf's specification for the `Timestamp` type.
+    const MIN_SECS: i64 = -62135596800;
+    // Unix timestamp for 9999-12-31 23:59:59, the maximum accepted by
+    // protobuf's specification for the `Timestamp` type.
+    const MAX_SECS: i64 = 253402300799;
+
+    let secs = monotonic_time.as_secs();
+    if !(MIN_SECS..=MAX_SECS).contains(&secs) {
+        return None;
+    }
+
+    Some(Timestamp {
+        seconds: secs,
+        nanos: monotonic_time.subsec_nanos() as i32,
+    })
+}
+
+/// Attempts a cast from a protobuf `Timestamp` to a `MonotonicTime`.
+///
+/// This should never fail provided that the `Timestamp` complies with the
+/// protobuf specification. It can only fail if the nanosecond part is negative
+/// or greater than 999'999'999.
+fn timestamp_to_monotonic(timestamp: Timestamp) -> Option<MonotonicTime> {
+    let nanos: u32 = timestamp.nanos.try_into().ok()?;
+
+    MonotonicTime::new(timestamp.seconds, nanos)
+}
+
+/// Attempts a cast from a protobuf `Duration` to a `std::time::Duration`.
+///
+/// If the `Duration` complies with the protobuf specification, this can only
+/// fail if the duration is negative.
+fn to_positive_duration(duration: prost_types::Duration) -> Option<Duration> {
+    if duration.seconds < 0 || duration.nanos < 0 {
+        return None;
+    }
+
+    Some(Duration::new(
+        duration.seconds as u64,
+        duration.nanos as u32,
+    ))
+}
+
+/// Attempts a cast from a protobuf `Duration` to a strictly positive
+/// `std::time::Duration`.
+///
+/// If the `Duration` complies with the protobuf specification, this can only
+/// fail if the duration is negative or null.
+fn to_strictly_positive_duration(duration: prost_types::Duration) -> Option<Duration> {
+    if duration.seconds < 0 || duration.nanos < 0 || (duration.seconds == 0 && duration.nanos == 0)
+    {
+        return None;
+    }
+
+    Some(Duration::new(
+        duration.seconds as u64,
+        duration.nanos as u32,
+    ))
+}

asynchronix/src/rpc/grpc.rs

@@ -0,0 +1,146 @@
+//! GRPC simulation server.
+
+use std::net::SocketAddr;
+use std::sync::Mutex;
+use std::sync::MutexGuard;
+
+use tonic::{transport::Server, Request, Response, Status};
+
+use crate::rpc::EndpointRegistry;
+use crate::simulation::SimInit;
+
+use super::codegen::simulation::*;
+use super::generic_server::GenericServer;
+
+/// Runs a GRPC simulation server.
+///
+/// The first argument is a closure that is called every time the simulation is
+/// started by the remote client. It must create a new `SimInit` object
+/// complemented by a registry that exposes the public event and query
+/// interface.
+pub fn run<F>(sim_gen: F, addr: SocketAddr) -> Result<(), Box<dyn std::error::Error>>
+where
+    F: FnMut() -> (SimInit, EndpointRegistry) + Send + 'static,
+{
+    // Use a single-threaded server.
+    let rt = tokio::runtime::Builder::new_current_thread().build()?;
+
+    let sim_manager = GrpcServer::new(sim_gen);
+
+    rt.block_on(async move {
+        Server::builder()
+            .add_service(simulation_server::SimulationServer::new(sim_manager))
+            .serve(addr)
+            .await?;
+
+        Ok(())
+    })
+}
+
+struct GrpcServer<F>
+where
+    F: FnMut() -> (SimInit, EndpointRegistry) + Send + 'static,
+{
+    inner: Mutex<GenericServer<F>>,
+}
+
+impl<F> GrpcServer<F>
+where
+    F: FnMut() -> (SimInit, EndpointRegistry) + Send + 'static,
+{
+    fn new(sim_gen: F) -> Self {
+        Self {
+            inner: Mutex::new(GenericServer::new(sim_gen)),
+        }
+    }
+
+    fn inner(&self) -> MutexGuard<'_, GenericServer<F>> {
+        self.inner.lock().unwrap()
+    }
+}
+
+#[tonic::async_trait]
+impl<F> simulation_server::Simulation for GrpcServer<F>
+where
+    F: FnMut() -> (SimInit, EndpointRegistry) + Send + 'static,
+{
+    async fn init(&self, request: Request<InitRequest>) -> Result<Response<InitReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().init(request)))
+    }
+    async fn time(&self, request: Request<TimeRequest>) -> Result<Response<TimeReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().time(request)))
+    }
+    async fn step(&self, request: Request<StepRequest>) -> Result<Response<StepReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().step(request)))
+    }
+    async fn step_until(
+        &self,
+        request: Request<StepUntilRequest>,
+    ) -> Result<Response<StepUntilReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().step_until(request)))
+    }
+    async fn schedule_event(
+        &self,
+        request: Request<ScheduleEventRequest>,
+    ) -> Result<Response<ScheduleEventReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().schedule_event(request)))
+    }
+    async fn cancel_event(
+        &self,
+        request: Request<CancelEventRequest>,
+    ) -> Result<Response<CancelEventReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().cancel_event(request)))
+    }
+    async fn process_event(
+        &self,
+        request: Request<ProcessEventRequest>,
+    ) -> Result<Response<ProcessEventReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().process_event(request)))
+    }
+    async fn process_query(
+        &self,
+        request: Request<ProcessQueryRequest>,
+    ) -> Result<Response<ProcessQueryReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().process_query(request)))
+    }
+    async fn read_events(
+        &self,
+        request: Request<ReadEventsRequest>,
+    ) -> Result<Response<ReadEventsReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().read_events(request)))
+    }
+    async fn open_sink(
+        &self,
+        request: Request<OpenSinkRequest>,
+    ) -> Result<Response<OpenSinkReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().open_sink(request)))
+    }
+    async fn close_sink(
+        &self,
+        request: Request<CloseSinkRequest>,
+    ) -> Result<Response<CloseSinkReply>, Status> {
+        let request = request.into_inner();
+
+        Ok(Response::new(self.inner().close_sink(request)))
+    }
+}

asynchronix/src/rpc/key_registry.rs

@@ -0,0 +1,47 @@
+use crate::time::{ActionKey, MonotonicTime};
+use crate::util::indexed_priority_queue::{IndexedPriorityQueue, InsertKey};
+
+pub(crate) type KeyRegistryId = InsertKey;
+
+/// A collection of `ActionKey`s indexed by a unique identifier.
+#[derive(Default)]
+pub(crate) struct KeyRegistry {
+    keys: IndexedPriorityQueue<MonotonicTime, ActionKey>,
+}
+
+impl KeyRegistry {
+    /// Inserts an `ActionKey` into the registry.
+    ///
+    /// The provided expiration deadline is the latest time at which the key may
+    /// still be active.
+    pub(crate) fn insert_key(
+        &mut self,
+        action_key: ActionKey,
+        expiration: MonotonicTime,
+    ) -> KeyRegistryId {
+        self.keys.insert(expiration, action_key)
+    }
+
+    /// Inserts a non-expiring `ActionKey` into the registry.
+    pub(crate) fn insert_eternal_key(&mut self, action_key: ActionKey) -> KeyRegistryId {
+        self.keys.insert(MonotonicTime::MAX, action_key)
+    }
+
+    /// Removes an `ActionKey` from the registry and returns it.
+    ///
+    /// Returns `None` if the key was not found in the registry.
+    pub(crate) fn extract_key(&mut self, key_id: KeyRegistryId) -> Option<ActionKey> {
+        self.keys.extract(key_id).map(|(_, key)| key)
+    }
+
+    /// Remove keys with an expiration deadline strictly predating the argument.
+    pub(crate) fn remove_expired_keys(&mut self, now: MonotonicTime) {
+        while let Some(expiration) = self.keys.peek_key() {
+            if *expiration >= now {
+                return;
+            }
+
+            self.keys.pull();
+        }
+    }
+}