added activity_fairing for webserver

src/activity_fairing.rs

@@ -0,0 +1,46 @@
+use std::time::Duration;
+
+use log::error;
+use rocket::{
+    Data, Request,
+    fairing::{Fairing, Info, Kind},
+};
+use tokio::{sync::mpsc, time::timeout};
+
+pub struct ActivityNotifier {
+    pub sender: mpsc::Sender<()>,
+}
+
+#[rocket::async_trait]
+impl Fairing for ActivityNotifier {
+    fn info(&self) -> Info {
+        Info {
+            name: "Keeps track of time since the last request",
+            kind: Kind::Request | Kind::Response,
+        }
+    }
+
+    async fn on_request(&self, _: &mut Request<'_>, _: &mut Data<'_>) {
+        error!("on_request");
+        let _ = self.sender.try_send(());
+    }
+}
+
+pub fn spawn_idle_watcher<F>(idle_duration: Duration, mut on_idle: F) -> mpsc::Sender<()>
+where
+    F: FnMut() + Send + 'static,
+{
+    let (tx, mut rx) = mpsc::channel::<()>(100);
+
+    tokio::spawn(async move {
+        loop {
+            let idle = timeout(idle_duration, rx.recv()).await;
+            if idle.is_err() {
+                // No activity received in the duration
+                on_idle();
+            }
+        }
+    });
+
+    tx
+}