mixnode: graceful shutdown on ctrl-c (#1304)

* mixnode: add graceful notification to most tasks

* Add note about remaining work

* task/shutdown: add shutdown timer

* changelog: add entry for shutdown

* mixnode: revert some temp changes

* common/task: make sure to use latest tokio

mixnode/src/node/packet_delayforwarder.rs

@@ -9,6 +9,8 @@ use nymsphinx::forwarding::packet::MixPacket;
 use std::io;
 use tokio::time::Instant;
 
+use super::ShutdownListener;
+
 // Delay + MixPacket vs Instant + MixPacket
 
 // rather than using Duration directly, we use an Instant, this way we minimise skew due to
@@ -26,13 +28,18 @@ where
     packet_sender: PacketDelayForwardSender,
     packet_receiver: PacketDelayForwardReceiver,
     node_stats_update_sender: UpdateSender,
+    shutdown: ShutdownListener,
 }
 
 impl<C> DelayForwarder<C>
 where
     C: mixnet_client::SendWithoutResponse,
 {
-    pub(crate) fn new(client: C, node_stats_update_sender: UpdateSender) -> DelayForwarder<C> {
+    pub(crate) fn new(
+        client: C,
+        node_stats_update_sender: UpdateSender,
+        shutdown: ShutdownListener,
+    ) -> DelayForwarder<C> {
         let (packet_sender, packet_receiver) = mpsc::unbounded();
 
         DelayForwarder::<C> {
@@ -41,6 +48,7 @@ where
             packet_sender,
             packet_receiver,
             node_stats_update_sender,
+            shutdown,
         }
     }
 
@@ -97,6 +105,7 @@ where
     }
 
     pub(crate) async fn run(&mut self) {
+        log::trace!("Starting DelayForwarder");
         loop {
             tokio::select! {
                 delayed = self.delay_queue.next() => {
@@ -107,8 +116,13 @@ where
                     // and hence it can't happen that ALL senders are dropped
                     self.handle_new_packet(new_packet.unwrap())
                 }
+                _ = self.shutdown.recv() => {
+                    log::trace!("DelayForwarder: Received shutdown");
+                    break;
+                }
             }
         }
+        log::trace!("DelayForwarder: Exiting");
     }
 }
 
@@ -120,6 +134,8 @@ mod tests {
     use std::sync::{Arc, Mutex};
     use std::time::Duration;
 
+    use task::ShutdownNotifier;
+
     use nymsphinx::addressing::nodes::NymNodeRoutingAddress;
     use nymsphinx_params::packet_sizes::PacketSize;
     use nymsphinx_params::PacketMode;
@@ -189,7 +205,9 @@ mod tests {
         let node_stats_update_sender = UpdateSender::new(stats_sender);
         let client = TestClient::default();
         let client_packets_sent = client.packets_sent.clone();
-        let mut delay_forwarder = DelayForwarder::new(client, node_stats_update_sender);
+        let shutdown = ShutdownNotifier::default();
+        let mut delay_forwarder =
+            DelayForwarder::new(client, node_stats_update_sender, shutdown.subscribe());
         let packet_sender = delay_forwarder.sender();
 
         // Spawn the worker, listening on packet_sender channel