Implement simple networking layer for RaftMetadataStore

This fixes restatedev#1803.

crates/metadata-store/Cargo.toml

@@ -23,6 +23,7 @@ async-trait = { workspace = true }
 bytes = { workspace = true }
 bytestring = { workspace = true }
 derive_builder = { workspace = true }
+derive_more = { workspace = true }
 futures = { workspace = true }
 http = { workspace = true }
 humantime = { workspace = true }

crates/metadata-store/build.rs

@@ -21,5 +21,11 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .protoc_arg("--experimental_allow_proto3_optional")
         .compile_protos(&["./proto/metadata_store_svc.proto"], &["proto"])?;
 
+    tonic_build::configure()
+        .bytes(["."])
+        .file_descriptor_set_path(out_dir.join("raft_metadata_store_svc.bin"))
+        .protoc_arg("--experimental_allow_proto3_optional")
+        .compile_protos(&["./proto/raft_metadata_store_svc.proto"], &["proto"])?;
+
     Ok(())
 }

crates/metadata-store/proto/raft_metadata_store_svc.proto

@@ -0,0 +1,24 @@
+// Copyright (c) 2024 - Restate Software, Inc., Restate GmbH
+//
+// This file is part of the Restate service protocol, which is
+// released under the MIT license.
+//
+// You can find a copy of the license in file LICENSE in the root
+// directory of this repository or package, or at
+// https://github.com/restatedev/proto/blob/main/LICENSE
+
+syntax = "proto3";
+
+import "google/protobuf/empty.proto";
+
+package dev.restate.raft_metadata_store_svc;
+
+// Grpc service definition for the RaftMetadataStore implementation.
+service RaftMetadataStoreSvc {
+  rpc Raft(stream RaftMessage) returns (stream RaftMessage);
+}
+
+message RaftMessage {
+  bytes message = 1;
+}
+

crates/metadata-store/src/raft/connection_manager.rs

@@ -0,0 +1,188 @@
+// Copyright (c) 2024 - Restate Software, Inc., Restate GmbH.
+// All rights reserved.
+//
+// Use of this software is governed by the Business Source License
+// included in the LICENSE file.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0.
+
+use crate::raft::grpc_svc::RaftMessage;
+use futures::StreamExt;
+use protobuf::Message as ProtobufMessage;
+use raft::prelude::Message;
+use restate_core::{cancellation_watcher, ShutdownError, TaskCenter, TaskKind};
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+use tokio::sync::mpsc;
+use tokio::sync::mpsc::error::TrySendError;
+use tokio_stream::wrappers::ReceiverStream;
+use tonic::codegen::BoxStream;
+use tracing::{debug, instrument};
+
+#[derive(Debug, thiserror::Error)]
+pub enum ConnectionError {
+    #[error("internal error: {0}")]
+    Internal(String),
+    #[error(transparent)]
+    Shutdown(#[from] ShutdownError),
+}
+
+#[derive(Clone, derive_more::Debug)]
+pub struct ConnectionManager {
+    inner: Arc<ConnectionManagerInner>,
+}
+
+impl ConnectionManager {
+    pub fn new(identity: u64, router: mpsc::Sender<Message>) -> Self {
+        ConnectionManager {
+            inner: Arc::new(ConnectionManagerInner::new(identity, router)),
+        }
+    }
+
+    pub fn identity(&self) -> u64 {
+        self.inner.identity
+    }
+
+    pub fn accept_connection(
+        &self,
+        raft_peer: u64,
+        incoming_rx: tonic::Streaming<RaftMessage>,
+    ) -> Result<BoxStream<RaftMessage>, ConnectionError> {
+        let (outgoing_tx, outgoing_rx) = mpsc::channel(128);
+        self.run_connection(raft_peer, outgoing_tx, incoming_rx)?;
+
+        let outgoing_stream = ReceiverStream::new(outgoing_rx)
+            .map(Result::<_, tonic::Status>::Ok)
+            .boxed();
+        Ok(outgoing_stream)
+    }
+
+    pub fn run_connection(
+        &self,
+        remote_peer: u64,
+        outgoing_tx: mpsc::Sender<RaftMessage>,
+        incoming_rx: tonic::Streaming<RaftMessage>,
+    ) -> Result<(), ConnectionError> {
+        let mut guard = self.inner.connections.lock().unwrap();
+
+        if guard.contains_key(&remote_peer) {
+            // we already have a connection established to remote peer
+            return Ok(());
+        }
+
+        let connection = Connection::new(outgoing_tx);
+        guard.insert(remote_peer, connection);
+
+        let reactor = ConnectionReactor {
+            remote_peer,
+            connection_manager: Arc::clone(&self.inner),
+        };
+
+        let _task_id = TaskCenter::spawn_child(
+            TaskKind::ConnectionReactor,
+            "raft-connection-reactor",
+            reactor.run(incoming_rx),
+        )?;
+
+        Ok(())
+    }
+
+    pub fn get_connection(&self, target: u64) -> Option<Connection> {
+        self.inner.connections.lock().unwrap().get(&target).cloned()
+    }
+}
+
+struct ConnectionReactor {
+    remote_peer: u64,
+    connection_manager: Arc<ConnectionManagerInner>,
+}
+
+impl ConnectionReactor {
+    #[instrument(level = "debug", skip_all, fields(remote_peer = %self.remote_peer))]
+    async fn run(self, mut incoming_rx: tonic::Streaming<RaftMessage>) -> anyhow::Result<()> {
+        let mut shutdown = std::pin::pin!(cancellation_watcher());
+        debug!("Run connection reactor");
+
+        loop {
+            tokio::select! {
+                _ = &mut shutdown => {
+                    break;
+                },
+                message = incoming_rx.next() => {
+                    match message {
+                        Some(message) => {
+                            match message {
+                                Ok(message) => {
+                                    let message = Message::parse_from_carllerche_bytes(&message.message)?;
+
+                                    assert_eq!(message.to, self.connection_manager.identity, "Expect to only receive messages for peer '{}'", self.connection_manager.identity);
+
+                                    if self.connection_manager.router.send(message).await.is_err() {
+                                        // system is shutting down
+                                        debug!("System is shutting down; closing connection");
+                                        break;
+                                    }
+                                }
+                                Err(err) => {
+                                    debug!("Closing connection because received error: {err}");
+                                    break;
+                                }
+                            }
+                        }
+                        None => {
+                            debug!("Remote peer closed connection");
+                            break
+                        },
+                    }
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl Drop for ConnectionReactor {
+    fn drop(&mut self) {
+        debug!(remote_peer = %self.remote_peer, "Close connection");
+        self.connection_manager
+            .connections
+            .lock()
+            .expect("shouldn't be poisoned")
+            .remove(&self.remote_peer);
+    }
+}
+
+#[derive(Debug)]
+struct ConnectionManagerInner {
+    identity: u64,
+    connections: Mutex<HashMap<u64, Connection>>,
+    router: mpsc::Sender<Message>,
+}
+
+impl ConnectionManagerInner {
+    pub fn new(identity: u64, router: mpsc::Sender<Message>) -> Self {
+        ConnectionManagerInner {
+            identity,
+            router,
+            connections: Mutex::default(),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Connection {
+    tx: mpsc::Sender<RaftMessage>,
+}
+
+impl Connection {
+    pub fn new(tx: mpsc::Sender<RaftMessage>) -> Self {
+        Connection { tx }
+    }
+
+    pub fn try_send(&self, message: RaftMessage) -> Result<(), TrySendError<RaftMessage>> {
+        self.tx.try_send(message)
+    }
+}

crates/metadata-store/src/raft/grpc_svc.rs

@@ -0,0 +1,14 @@
+// Copyright (c) 2024 - Restate Software, Inc., Restate GmbH.
+// All rights reserved.
+//
+// Use of this software is governed by the Business Source License
+// included in the LICENSE file.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0.
+
+tonic::include_proto!("dev.restate.raft_metadata_store_svc");
+
+pub const FILE_DESCRIPTOR_SET: &[u8] =
+    tonic::include_file_descriptor_set!("raft_metadata_store_svc");

crates/metadata-store/src/raft/handler.rs

@@ -0,0 +1,67 @@
+// Copyright (c) 2024 - Restate Software, Inc., Restate GmbH.
+// All rights reserved.
+//
+// Use of this software is governed by the Business Source License
+// included in the LICENSE file.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0.
+
+use crate::raft::connection_manager::{ConnectionError, ConnectionManager};
+use crate::raft::grpc_svc::raft_metadata_store_svc_server::RaftMetadataStoreSvc;
+use crate::raft::grpc_svc::RaftMessage;
+use std::str::FromStr;
+use tonic::codegen::BoxStream;
+use tonic::{Request, Response, Status, Streaming};
+
+pub const RAFT_PEER_METADATA_KEY: &str = "x-restate-raft-peer";
+
+#[derive(Debug)]
+pub struct RaftMetadataStoreHandler {
+    connection_manager: ConnectionManager,
+}
+
+impl RaftMetadataStoreHandler {
+    pub fn new(connection_manager: ConnectionManager) -> Self {
+        Self { connection_manager }
+    }
+}
+
+#[async_trait::async_trait]
+impl RaftMetadataStoreSvc for RaftMetadataStoreHandler {
+    type RaftStream = BoxStream<RaftMessage>;
+
+    async fn raft(
+        &self,
+        request: Request<Streaming<RaftMessage>>,
+    ) -> Result<Response<Self::RaftStream>, Status> {
+        let raft_peer_metadata =
+            request
+                .metadata()
+                .get(RAFT_PEER_METADATA_KEY)
+                .ok_or(Status::invalid_argument(format!(
+                    "'{}' is missing",
+                    RAFT_PEER_METADATA_KEY
+                )))?;
+        let raft_peer = u64::from_str(
+            raft_peer_metadata
+                .to_str()
+                .map_err(|err| Status::invalid_argument(err.to_string()))?,
+        )
+        .map_err(|err| Status::invalid_argument(err.to_string()))?;
+        let outgoing_rx = self
+            .connection_manager
+            .accept_connection(raft_peer, request.into_inner())?;
+        Ok(Response::new(outgoing_rx))
+    }
+}
+
+impl From<ConnectionError> for Status {
+    fn from(value: ConnectionError) -> Self {
+        match value {
+            ConnectionError::Internal(err) => Status::internal(err),
+            ConnectionError::Shutdown(err) => Status::aborted(err.to_string()),
+        }
+    }
+}

crates/metadata-store/src/raft/mod.rs

@@ -8,6 +8,10 @@
 // the Business Source License, use of this software will be governed
 // by the Apache License, Version 2.0.
 
+mod connection_manager;
+pub mod grpc_svc;
+mod handler;
+mod networking;
 pub mod service;
 mod storage;
 mod store;