Finishing basic implementation

src/shutdown.rs

@@ -0,0 +1,49 @@
+use tokio::sync::broadcast;
+
+/// Listens for the server shutdown signal.
+///
+/// Shutdown is signalled using a `broadcast::Receiver`. Only a single value is
+/// ever sent. Once a value has been sent via the broadcast channel, the server
+/// should shutdown.
+///
+/// The `Shutdown` struct listens for the signal and tracks that the signal has
+/// been received. Callers may query for whether the shutdown signal has been
+/// received or not.
+#[derive(Debug)]
+pub(crate) struct Shutdown {
+   /// `true` if the shutdown signal has been received
+   shutdown: bool,
+
+   /// The receive half of the channel used to listen for shutdown.
+   notify: broadcast::Receiver<()>,
+}
+
+impl Shutdown {
+   /// Create a new `Shutdown` backed by the given `broadcast::Receiver`.
+   pub(crate) fn new(notify: broadcast::Receiver<()>) -> Shutdown {
+      Shutdown {
+         shutdown: false,
+         notify,
+      }
+   }
+
+   /// Returns `true` if the shutdown signal has been received.
+   pub(crate) fn is_shutdown(&self) -> bool {
+      self.shutdown
+   }
+
+   /// Receive the shutdown notice, waiting if necessary.
+   pub(crate) async fn recv(&mut self) {
+      // If the shutdown signal has already been received, then return
+      // immediately.
+      if self.shutdown {
+         return;
+      }
+
+      // Cannot receive a "lag error" as only one value is ever sent.
+      let _ = self.notify.recv().await;
+
+      // Remember that the signal has been received.
+      self.shutdown = true;
+   }
+}