slim_controller/

service.rs

// Copyright AGNTCY Contributors (https://github.com/agntcy)
// SPDX-License-Identifier: Apache-2.0

use std::collections::HashMap;
use std::pin::Pin;
use std::sync::Arc;

use slim_config::component::id::ID;
use slim_config::grpc::server::ServerConfig;
use tokio::sync::mpsc;
use tokio_stream::{Stream, StreamExt, wrappers::ReceiverStream};
use tokio_util::sync::CancellationToken;
use tonic::{Request, Response, Status};
use tracing::{debug, error, info};

use crate::api::proto::api::v1::control_message::Payload;
use crate::api::proto::api::v1::controller_service_server::ControllerServiceServer;
use crate::api::proto::api::v1::{
    self, ConnectionListResponse, ConnectionType, SubscriptionListResponse,
};
use crate::api::proto::api::v1::{
    Ack, ConnectionEntry, ControlMessage, SubscriptionEntry,
    controller_service_client::ControllerServiceClient,
    controller_service_server::ControllerService as GrpcControllerService,
};
use crate::errors::ControllerError;
use slim_config::grpc::client::ClientConfig;
use slim_datapath::api::ProtoMessage as PubsubMessage;
use slim_datapath::message_processing::MessageProcessor;
use slim_datapath::messages::Name;
use slim_datapath::messages::utils::SlimHeaderFlags;
use slim_datapath::tables::SubscriptionTable;

type TxChannel = mpsc::Sender<Result<ControlMessage, Status>>;
type TxChannels = HashMap<String, TxChannel>;

/// Inner structure for the controller service
/// This structure holds the internal state of the controller service,
/// including the ID, message processor, connections, and channels.
/// It is normally wrapped in an Arc to allow shared ownership across multiple threads.
#[derive(Debug)]
struct ControllerServiceInternal {
    /// ID of this SLIM instance
    id: ID,

    /// underlying message processor
    message_processor: Arc<MessageProcessor>,

    /// map of connection IDs to their configuration
    connections: Arc<parking_lot::RwLock<HashMap<String, u64>>>,

    /// channel to send messages into the datapath
    tx_slim: mpsc::Sender<Result<PubsubMessage, Status>>,

    /// channel to receive messages from the datapath
    _rx_slim: mpsc::Receiver<Result<PubsubMessage, Status>>,

    /// channels to send control messages
    tx_channels: parking_lot::RwLock<TxChannels>,

    /// cancellation token for graceful shutdown
    cancellation_tokens: parking_lot::RwLock<HashMap<String, CancellationToken>>,

    /// drain watch channel
    drain_rx: drain::Watch,
}

#[derive(Debug, Clone)]
struct ControllerService {
    /// internal service state
    inner: Arc<ControllerServiceInternal>,
}

/// The ControlPlane service is the main entry point for the controller service.
#[derive(Debug)]
pub struct ControlPlane {
    /// servers
    servers: Vec<ServerConfig>,

    /// clients
    clients: Vec<ClientConfig>,

    /// controller
    controller: ControllerService,
}

/// ControllerServiceInternal implements Drop trait to cancel all running listeners and
/// clean up resources.
impl Drop for ControlPlane {
    fn drop(&mut self) {
        // cancel all running listeners
        for (_endpoint, token) in self.controller.inner.cancellation_tokens.write().drain() {
            token.cancel();
        }
    }
}

/// ControlPlane implements the service trait for the controller service.
impl ControlPlane {
    /// Create a new ControlPlane service instance
    /// This function initializes the ControlPlane with the given ID, servers, clients, and message processor.
    /// It also sets up the internal state, including the connections and channels.
    /// # Arguments
    /// * `id` - The ID of the SLIM instance.
    /// * `servers` - A vector of server configurations.
    /// * `clients` - A vector of client configurations.
    /// * `drain_rx` - A drain watch channel for graceful shutdown.
    /// * `message_processor` - An Arc to the message processor instance.
    /// # Returns
    /// A new instance of ControlPlane.
    pub fn new(
        id: ID,
        servers: Vec<ServerConfig>,
        clients: Vec<ClientConfig>,
        drain_rx: drain::Watch,
        message_processor: Arc<MessageProcessor>,
    ) -> Self {
        // create local connection with the message processor
        let (_, tx_slim, rx_slim) = message_processor.register_local_connection();

        ControlPlane {
            servers,
            clients,
            controller: ControllerService {
                inner: Arc::new(ControllerServiceInternal {
                    id,
                    message_processor,
                    connections: Arc::new(parking_lot::RwLock::new(HashMap::new())),
                    tx_slim,
                    _rx_slim: rx_slim,
                    tx_channels: parking_lot::RwLock::new(HashMap::new()),
                    cancellation_tokens: parking_lot::RwLock::new(HashMap::new()),
                    drain_rx,
                }),
            },
        }
    }

    /// Take an existing ControlPlane instance and return a new one with the provided clients.
    pub fn with_clients(mut self, clients: Vec<ClientConfig>) -> Self {
        self.clients = clients;
        self
    }

    /// Take an existing ControlPlane instance and return a new one with the provided servers.
    pub fn with_servers(mut self, servers: Vec<ServerConfig>) -> Self {
        self.servers = servers;
        self
    }

    /// Run the clients and servers of the ControlPlane service.
    /// This function starts all the servers and clients defined in the ControlPlane.
    /// # Returns
    /// A Result indicating success or failure of the operation.
    /// # Errors
    /// If there is an error starting any of the servers or clients, it will return a ControllerError.
    pub async fn run(&mut self) -> Result<(), ControllerError> {
        info!("starting controller service");

        // Collect servers to avoid borrowing self both mutably and immutably
        let servers = self.servers.clone();
        let clients = self.clients.clone();

        // run all servers
        for server in servers {
            self.run_server(server)?;
        }

        // run all clients
        for client in clients {
            self.run_client(client).await?;
        }

        Ok(())
    }

    /// Stop the ControlPlane service.
    /// This function stops all running listeners and cancels any ongoing operations.
    /// It cleans up the internal state and ensures that all resources are released properly.
    pub fn stop(&mut self) {
        info!("stopping controller service");

        // cancel all running listeners
        for (endpoint, token) in self.controller.inner.cancellation_tokens.write().drain() {
            info!(%endpoint, "stopping");
            token.cancel();
        }
    }

    /// Run a client configuration.
    /// This function connects to the control plane using the provided client configuration.
    /// It checks if the client is already running and if not, it starts a new connection.
    async fn run_client(&mut self, client: ClientConfig) -> Result<(), ControllerError> {
        if self
            .controller
            .inner
            .cancellation_tokens
            .read()
            .contains_key(&client.endpoint)
        {
            return Err(ControllerError::ConfigError(format!(
                "client {} is already running",
                client.endpoint
            )));
        }

        let cancellation_token = CancellationToken::new();

        let tx = self
            .controller
            .connect(client.clone(), cancellation_token.clone())
            .await?;

        // Store the cancellation token in the controller service
        self.controller
            .inner
            .cancellation_tokens
            .write()
            .insert(client.endpoint.clone(), cancellation_token);

        // Store the sender in the tx_channels map
        self.controller
            .inner
            .tx_channels
            .write()
            .insert(client.endpoint.clone(), tx);

        // return the sender for control messages
        Ok(())
    }

    /// Run a server configuration.
    /// This function starts a server using the provided server configuration.
    /// It checks if the server is already running and if not, it starts a new server.
    pub fn run_server(&mut self, config: ServerConfig) -> Result<(), ControllerError> {
        info!(%config.endpoint, "starting control plane server");

        // Check if the server is already running
        if self
            .controller
            .inner
            .cancellation_tokens
            .read()
            .contains_key(&config.endpoint)
        {
            error!("server {} is already running", config.endpoint);
            return Err(ControllerError::ConfigError(format!(
                "server {} is already running",
                config.endpoint
            )));
        }

        let token = config
            .run_server(
                &[ControllerServiceServer::new(self.controller.clone())],
                self.controller.inner.drain_rx.clone(),
            )
            .map_err(|e| {
                error!("failed to run server {}: {}", config.endpoint, e);
                ControllerError::ConfigError(e.to_string())
            })?;

        // Store the cancellation token in the controller service
        self.controller
            .inner
            .cancellation_tokens
            .write()
            .insert(config.endpoint.clone(), token.clone());

        info!(%config.endpoint, "control plane server started");

        Ok(())
    }
}

impl ControllerService {
    const MAX_RETRIES: i32 = 10;

    /// Handle new control messages.
    async fn handle_new_control_message(
        &self,
        msg: ControlMessage,
        tx: &mpsc::Sender<Result<ControlMessage, Status>>,
    ) -> Result<(), ControllerError> {
        match msg.payload {
            Some(ref payload) => {
                match payload {
                    Payload::ConfigCommand(config) => {
                        for conn in &config.connections_to_create {
                            info!("received a connection to create: {:?}", conn);
                            let client_config =
                                serde_json::from_str::<ClientConfig>(&conn.config_data)
                                    .map_err(|e| ControllerError::ConfigError(e.to_string()))?;
                            let client_endpoint = &client_config.endpoint;

                            // connect to an endpoint if it's not already connected
                            if !self.inner.connections.read().contains_key(client_endpoint) {
                                match client_config.to_channel() {
                                    Err(e) => {
                                        error!("error reading channel config {:?}", e);
                                    }
                                    Ok(channel) => {
                                        let ret = self
                                            .inner
                                            .message_processor
                                            .connect(
                                                channel,
                                                Some(client_config.clone()),
                                                None,
                                                None,
                                            )
                                            .await
                                            .map_err(|e| {
                                                ControllerError::ConnectionError(e.to_string())
                                            });

                                        let conn_id = match ret {
                                            Err(e) => {
                                                error!("connection error: {:?}", e);
                                                return Err(ControllerError::ConnectionError(
                                                    e.to_string(),
                                                ));
                                            }
                                            Ok(conn_id) => conn_id.1,
                                        };

                                        self.inner
                                            .connections
                                            .write()
                                            .insert(client_endpoint.clone(), conn_id);
                                    }
                                }
                            }
                        }

                        for subscription in &config.subscriptions_to_set {
                            if !self
                                .inner
                                .connections
                                .read()
                                .contains_key(&subscription.connection_id)
                            {
                                error!("connection {} not found", subscription.connection_id);
                                continue;
                            }

                            let conn = self
                                .inner
                                .connections
                                .read()
                                .get(&subscription.connection_id)
                                .cloned()
                                .unwrap();
                            let source = Name::from_strings([
                                subscription.component_0.as_str(),
                                subscription.component_1.as_str(),
                                subscription.component_2.as_str(),
                            ])
                            .with_id(0);
                            let name = Name::from_strings([
                                subscription.component_0.as_str(),
                                subscription.component_1.as_str(),
                                subscription.component_2.as_str(),
                            ])
                            .with_id(subscription.id.unwrap_or(Name::NULL_COMPONENT));

                            let msg = PubsubMessage::new_subscribe(
                                &source,
                                &name,
                                Some(SlimHeaderFlags::default().with_recv_from(conn)),
                            );

                            if let Err(e) = self.send_control_message(msg).await {
                                error!("failed to subscribe: {}", e);
                            }
                        }

                        for subscription in &config.subscriptions_to_delete {
                            if !self
                                .inner
                                .connections
                                .read()
                                .contains_key(&subscription.connection_id)
                            {
                                error!("connection {} not found", subscription.connection_id);
                                continue;
                            }

                            let conn = self
                                .inner
                                .connections
                                .read()
                                .get(&subscription.connection_id)
                                .cloned()
                                .unwrap();
                            let source = Name::from_strings([
                                subscription.component_0.as_str(),
                                subscription.component_1.as_str(),
                                subscription.component_2.as_str(),
                            ])
                            .with_id(0);
                            let name = Name::from_strings([
                                subscription.component_0.as_str(),
                                subscription.component_1.as_str(),
                                subscription.component_2.as_str(),
                            ])
                            .with_id(subscription.id.unwrap_or(Name::NULL_COMPONENT));

                            let msg = PubsubMessage::new_unsubscribe(
                                &source,
                                &name,
                                Some(SlimHeaderFlags::default().with_recv_from(conn)),
                            );

                            if let Err(e) = self.send_control_message(msg).await {
                                error!("failed to unsubscribe: {}", e);
                            }
                        }

                        let ack = Ack {
                            original_message_id: msg.message_id.clone(),
                            success: true,
                            messages: vec![],
                        };

                        let reply = ControlMessage {
                            message_id: uuid::Uuid::new_v4().to_string(),
                            payload: Some(Payload::Ack(ack)),
                        };

                        if let Err(e) = tx.send(Ok(reply)).await {
                            error!("failed to send ACK: {}", e);
                        }
                    }
                    Payload::SubscriptionListRequest(_) => {
                        const CHUNK_SIZE: usize = 100;

                        let conn_table = self.inner.message_processor.connection_table();
                        let mut entries = Vec::new();

                        self.inner.message_processor.subscription_table().for_each(
                            |name, id, local, remote| {
                                let mut entry = SubscriptionEntry {
                                    component_0: name.components_strings().unwrap()[0].to_string(),
                                    component_1: name.components_strings().unwrap()[1].to_string(),
                                    component_2: name.components_strings().unwrap()[2].to_string(),
                                    id: Some(id),
                                    ..Default::default()
                                };

                                for &cid in local {
                                    entry.local_connections.push(ConnectionEntry {
                                        id: cid,
                                        connection_type: ConnectionType::Local as i32,
                                        config_data: "{}".to_string(),
                                    });
                                }

                                for &cid in remote {
                                    if let Some(conn) = conn_table.get(cid as usize) {
                                        entry.remote_connections.push(ConnectionEntry {
                                            id: cid,
                                            connection_type: ConnectionType::Remote as i32,
                                            config_data: match conn.config_data() {
                                                Some(data) => serde_json::to_string(data)
                                                    .unwrap_or_else(|_| "{}".to_string()),
                                                None => "{}".to_string(),
                                            },
                                        });
                                    } else {
                                        error!("no connection entry for id {}", cid);
                                    }
                                }
                                entries.push(entry);
                            },
                        );

                        for chunk in entries.chunks(CHUNK_SIZE) {
                            let resp = ControlMessage {
                                message_id: uuid::Uuid::new_v4().to_string(),
                                payload: Some(Payload::SubscriptionListResponse(
                                    SubscriptionListResponse {
                                        entries: chunk.to_vec(),
                                    },
                                )),
                            };

                            if let Err(e) = tx.try_send(Ok(resp)) {
                                error!("failed to send subscription batch: {}", e);
                            }
                        }
                    }
                    Payload::ConnectionListRequest(_) => {
                        let mut all_entries = Vec::new();
                        self.inner
                            .message_processor
                            .connection_table()
                            .for_each(|id, conn| {
                                all_entries.push(ConnectionEntry {
                                    id: id as u64,
                                    connection_type: ConnectionType::Remote as i32,
                                    config_data: match conn.config_data() {
                                        Some(data) => serde_json::to_string(data)
                                            .unwrap_or_else(|_| "{}".to_string()),
                                        None => "{}".to_string(),
                                    },
                                });
                            });

                        const CHUNK_SIZE: usize = 100;
                        for chunk in all_entries.chunks(CHUNK_SIZE) {
                            let resp = ControlMessage {
                                message_id: uuid::Uuid::new_v4().to_string(),
                                payload: Some(Payload::ConnectionListResponse(
                                    ConnectionListResponse {
                                        entries: chunk.to_vec(),
                                    },
                                )),
                            };

                            if let Err(e) = tx.try_send(Ok(resp)) {
                                error!("failed to send connection list batch: {}", e);
                            }
                        }
                    }
                    Payload::Ack(_ack) => {
                        // received an ack, do nothing - this should not happen
                    }
                    Payload::SubscriptionListResponse(_) => {
                        // received a subscription list response, do nothing - this should not happen
                    }
                    Payload::ConnectionListResponse(_) => {
                        // received a connection list response, do nothing - this should not happen
                    }
                    Payload::RegisterNodeRequest(_) => {
                        error!("received a register node request, this should not happen");
                    }
                    Payload::RegisterNodeResponse(_) => {
                        // received a register node response, do nothing
                    }
                    Payload::DeregisterNodeRequest(_) => {
                        error!("received a deregister node request, this should not happen");
                    }
                    Payload::DeregisterNodeResponse(_) => {
                        // received a deregister node response, do nothing
                    }
                }
            }
            None => {
                error!(
                    "received control message {} with no payload",
                    msg.message_id
                );
            }
        }

        Ok(())
    }

    /// Send a control message to SLIM.
    async fn send_control_message(&self, msg: PubsubMessage) -> Result<(), ControllerError> {
        self.inner.tx_slim.send(Ok(msg)).await.map_err(|e| {
            error!("error sending message into datapath: {}", e);
            ControllerError::DatapathError(e.to_string())
        })
    }

    /// Process the control message stream.
    fn process_control_message_stream(
        &self,
        config: Option<ClientConfig>,
        mut stream: impl Stream<Item = Result<ControlMessage, Status>> + Unpin + Send + 'static,
        tx: mpsc::Sender<Result<ControlMessage, Status>>,
        cancellation_token: CancellationToken,
    ) -> tokio::task::JoinHandle<()> {
        let this = self.clone();
        let drain = this.inner.drain_rx.clone();
        tokio::spawn(async move {
            // Send a register message to the control plane
            let endpoint = config
                .as_ref()
                .map(|c| c.endpoint.clone())
                .unwrap_or_else(|| "unknown".to_string());
            info!(%endpoint, "connected to control plane");

            let mut retry_connect = false;

            let register_request = ControlMessage {
                message_id: uuid::Uuid::new_v4().to_string(),
                payload: Some(Payload::RegisterNodeRequest(v1::RegisterNodeRequest {
                    node_id: this.inner.id.to_string(),
                })),
            };

            // send register request if client
            if config.is_some() {
                if let Err(e) = tx.send(Ok(register_request)).await {
                    error!("failed to send register request: {}", e);
                    return;
                }
            }

            // TODO; here we should wait for an ack

            loop {
                tokio::select! {
                    next = stream.next() => {
                        match next {
                            Some(Ok(msg)) => {
                                if let Err(e) = this.handle_new_control_message(msg, &tx).await {
                                    error!("error processing incoming control message: {:?}", e);
                                }
                            }
                            Some(Err(e)) => {
                                if let Some(io_err) = Self::match_for_io_error(&e) {
                                    if io_err.kind() == std::io::ErrorKind::BrokenPipe {
                                        info!("connection closed by peer");
                                        retry_connect = true;
                                    }
                                } else {
                                    error!(%e, "error receiving control messages");
                                }

                                break;
                            }
                            None => {
                                debug!("end of stream");
                                retry_connect = true;
                                break;
                            }
                        }
                    }
                    _ = cancellation_token.cancelled() => {
                        debug!("shutting down stream on cancellation token");
                        break;
                    }
                    _ = drain.clone().signaled() => {
                        debug!("shutting down stream on drain");
                        break;
                    }
                }
            }

            info!(%endpoint, "control plane stream closed");

            if retry_connect {
                if let Some(config) = config {
                    info!(%config.endpoint, "retrying connection to control plane");
                    this.connect(config.clone(), cancellation_token)
                        .await
                        .map_or_else(
                            |e| {
                                error!("failed to reconnect to control plane: {}", e);
                            },
                            |tx| {
                                info!(%config.endpoint, "reconnected to control plane");

                                this.inner
                                    .tx_channels
                                    .write()
                                    .insert(config.endpoint.clone(), tx);
                            },
                        )
                }
            }
        })
    }

    /// Connect to the control plane using the provided client configuration.
    /// This function attempts to establish a connection to the control plane and returns a sender for control messages.
    /// It retries the connection a specified number of times if it fails.
    async fn connect(
        &self,
        config: ClientConfig,
        cancellation_token: CancellationToken,
    ) -> Result<mpsc::Sender<Result<ControlMessage, Status>>, ControllerError> {
        info!(%config.endpoint, "connecting to control plane");

        let channel = config.to_channel().map_err(|e| {
            error!("error reading channel config: {}", e);
            ControllerError::ConfigError(e.to_string())
        })?;

        let mut client = ControllerServiceClient::new(channel);
        for i in 0..Self::MAX_RETRIES {
            let (tx, rx) = mpsc::channel::<Result<ControlMessage, Status>>(128);
            let out_stream = ReceiverStream::new(rx).map(|res| res.expect("mapping error"));
            match client.open_control_channel(Request::new(out_stream)).await {
                Ok(stream) => {
                    // process the control message stream
                    self.process_control_message_stream(
                        Some(config),
                        stream.into_inner(),
                        tx.clone(),
                        cancellation_token.clone(),
                    );

                    return Ok(tx);
                }
                Err(e) => {
                    error!(%e, "connection error, retrying {}/{}", i + 1, Self::MAX_RETRIES);
                }
            };

            // sleep 1 sec between each connection retry
            tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;
        }

        Err(ControllerError::ConfigError(format!(
            "failed to connect to control plane after {} retries",
            Self::MAX_RETRIES
        )))
    }

    fn match_for_io_error(err_status: &Status) -> Option<&std::io::Error> {
        let mut err: &(dyn std::error::Error + 'static) = err_status;

        loop {
            if let Some(io_err) = err.downcast_ref::<std::io::Error>() {
                return Some(io_err);
            }

            // h2::Error do not expose std::io::Error with `source()`
            // https://github.com/hyperium/h2/pull/462
            if let Some(h2_err) = err.downcast_ref::<h2::Error>() {
                if let Some(io_err) = h2_err.get_io() {
                    return Some(io_err);
                }
            }

            err = err.source()?;
        }
    }
}

#[tonic::async_trait]
impl GrpcControllerService for ControllerService {
    type OpenControlChannelStream =
        Pin<Box<dyn Stream<Item = Result<ControlMessage, Status>> + Send + 'static>>;

    async fn open_control_channel(
        &self,
        request: Request<tonic::Streaming<ControlMessage>>,
    ) -> Result<Response<Self::OpenControlChannelStream>, Status> {
        // Get the remote endpoint from the request metadata
        let remote_endpoint = request
            .remote_addr()
            .map(|addr| addr.to_string())
            .unwrap_or_else(|| "unknown".to_string());

        let stream = request.into_inner();
        let (tx, rx) = mpsc::channel::<Result<ControlMessage, Status>>(128);

        let cancellation_token = CancellationToken::new();

        self.process_control_message_stream(None, stream, tx.clone(), cancellation_token.clone());

        // store the sender in the tx_channels map
        self.inner
            .tx_channels
            .write()
            .insert(remote_endpoint.clone(), tx);

        // store the cancellation token in the controller service
        self.inner
            .cancellation_tokens
            .write()
            .insert(remote_endpoint.clone(), cancellation_token);

        let out_stream = ReceiverStream::new(rx);
        Ok(Response::new(
            Box::pin(out_stream) as Self::OpenControlChannelStream
        ))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use slim_config::component::id::Kind;
    use tracing_test::traced_test;

    #[tokio::test]
    #[traced_test]
    async fn test_end_to_end() {
        // Create an ID for slim instance
        let id_server =
            ID::new_with_name(Kind::new("slim").unwrap(), "test_server_instance").unwrap();
        let id_client =
            ID::new_with_name(Kind::new("slim").unwrap(), "test_client_instance").unwrap();

        // Create a server configuration
        let server_config = ServerConfig::with_endpoint("127.0.0.1:50051")
            .with_tls_settings(slim_config::tls::server::TlsServerConfig::insecure());

        // create a client configuration
        let client_config = ClientConfig::with_endpoint("http://127.0.0.1:50051")
            .with_tls_setting(slim_config::tls::client::TlsClientConfig::insecure());

        // create drain channels
        let (signal_server, watch_server) = drain::channel();
        let (signal_client, watch_client) = drain::channel();

        // Create a message processor
        let message_processor_client = MessageProcessor::with_drain_channel(watch_client.clone());
        let message_processor_server = MessageProcessor::with_drain_channel(watch_server.clone());

        // Create a control plane instance for server
        let mut control_plane_server = ControlPlane::new(
            id_server,
            vec![server_config],
            vec![],
            watch_server,
            Arc::new(message_processor_server),
        );

        let mut control_plane_client = ControlPlane::new(
            id_client,
            vec![],
            vec![client_config],
            watch_client,
            Arc::new(message_processor_client),
        );

        // Start the server
        control_plane_server.run().await.unwrap();

        // Sleep for a short duration to ensure the server is ready
        tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;

        // Start the client
        control_plane_client.run().await.unwrap();

        // Sleep for a short duration to ensure the client is ready
        tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;

        // Check if the server received the connection
        assert!(logs_contain(
            "received a register node request, this should not happen"
        ));

        // drop the server and the client. This should also cancel the running listeners
        // and close the connections gracefully.
        drop(control_plane_server);
        drop(control_plane_client);

        // Make sure there is nothing left to drain (this should not block)
        signal_server.drain().await;
        signal_client.drain().await;
    }
}