Delay dropping of zenoh communication layer to ensure that stop message is sent

Zenoh seems to drop the messages in its send queue when the session is closed. The stop messages are critical, so we wait a bit to ensure that they're actually sent.

apis/rust/node/src/communication/zenoh.rs

@@ -1,6 +1,6 @@
 use super::{CommunicationLayer, Publisher, Subscriber};
 use crate::BoxError;
-use std::sync::Arc;
+use std::{sync::Arc, time::Duration};
 use zenoh::{
     prelude::{EntityFactory, Priority, Receiver as _, SplitBuffer, ZFuture},
     publication::CongestionControl,
@@ -53,6 +53,17 @@ impl CommunicationLayer for ZenohCommunicationLayer {
     }
 }
 
+impl Drop for ZenohCommunicationLayer {
+    fn drop(&mut self) {
+        // wait a bit before closing to ensure that remaining published
+        // messages are sent out
+        //
+        // TODO: create a minimal example to reproduce the dropped messages
+        // and report this issue in the zenoh repo
+        std::thread::sleep(Duration::from_secs_f32(1.0));
+    }
+}
+
 #[derive(Clone)]
 pub struct ZenohPublisher {
     publisher: zenoh::publication::Publisher<'static>,