Add LivlinessSubscriber history option (#1355)

Author: OlivierHecart

examples/examples/z_sub_liveliness.rs

@@ -20,7 +20,7 @@ async fn main() {
     // Initiate logging
     zenoh::try_init_log_from_env();
 
-    let (config, key_expr) = parse_args();
+    let (config, key_expr, history) = parse_args();
 
     println!("Opening session...");
     let session = zenoh::open(config).await.unwrap();
@@ -30,6 +30,7 @@ async fn main() {
     let subscriber = session
         .liveliness()
         .declare_subscriber(&key_expr)
+        .history(history)
         .await
         .unwrap();
 
@@ -51,13 +52,16 @@ async fn main() {
 #[derive(clap::Parser, Clone, PartialEq, Eq, Hash, Debug)]
 struct Args {
     #[arg(short, long, default_value = "group1/**")]
-    /// The key expression to write to.
+    /// The key expression to subscribe to.
     key: KeyExpr<'static>,
+    #[arg(long)]
+    /// Get historical liveliness tokens.
+    history: bool,
     #[command(flatten)]
     common: CommonArgs,
 }
 
-fn parse_args() -> (Config, KeyExpr<'static>) {
+fn parse_args() -> (Config, KeyExpr<'static>, bool) {
     let args = Args::parse();
-    (args.common.into(), args.key)
+    (args.common.into(), args.key, args.history)
 }

zenoh/src/api/liveliness.rs

@@ -169,6 +169,7 @@ impl<'a> Liveliness<'a> {
             session: self.session.clone(),
             key_expr: TryIntoKeyExpr::try_into(key_expr).map_err(Into::into),
             handler: DefaultHandler::default(),
+            history: false,
         }
     }
 
@@ -439,6 +440,7 @@ pub struct LivelinessSubscriberBuilder<'a, 'b, Handler> {
     pub session: SessionRef<'a>,
     pub key_expr: ZResult<KeyExpr<'b>>,
     pub handler: Handler,
+    pub history: bool,
 }
 
 #[zenoh_macros::unstable]
@@ -473,11 +475,13 @@ impl<'a, 'b> LivelinessSubscriberBuilder<'a, 'b, DefaultHandler> {
             session,
             key_expr,
             handler: _,
+            history,
         } = self;
         LivelinessSubscriberBuilder {
             session,
             key_expr,
             handler: callback,
+            history,
         }
     }
 
@@ -544,11 +548,33 @@ impl<'a, 'b> LivelinessSubscriberBuilder<'a, 'b, DefaultHandler> {
             session,
             key_expr,
             handler: _,
+            history,
         } = self;
         LivelinessSubscriberBuilder {
             session,
             key_expr,
             handler,
+            history,
+        }
+    }
+}
+
+#[zenoh_macros::unstable]
+impl<Handler> LivelinessSubscriberBuilder<'_, '_, Handler> {
+    #[inline]
+    #[zenoh_macros::unstable]
+    pub fn history(self, history: bool) -> Self {
+        let LivelinessSubscriberBuilder {
+            session,
+            key_expr,
+            handler,
+            history: _,
+        } = self;
+        LivelinessSubscriberBuilder {
+            session,
+            key_expr,
+            handler,
+            history,
         }
     }
 }
@@ -576,7 +602,12 @@ where
         let session = self.session;
         let (callback, handler) = self.handler.into_handler();
         session
-            .declare_liveliness_subscriber_inner(&key_expr, Locality::default(), callback)
+            .declare_liveliness_subscriber_inner(
+                &key_expr,
+                Locality::default(),
+                self.history,
+                callback,
+            )
             .map(|sub_state| Subscriber {
                 subscriber: SubscriberInner {
                     session,

zenoh/src/api/session.rs

@@ -1428,6 +1428,7 @@ impl Session {
         &self,
         key_expr: &KeyExpr,
         origin: Locality,
+        history: bool,
         callback: Callback<'static, Sample>,
     ) -> ZResult<Arc<SubscriberState>> {
         let mut state = zwrite!(self.state);
@@ -1475,7 +1476,11 @@ impl Session {
 
         primitives.send_interest(Interest {
             id,
-            mode: InterestMode::Future,
+            mode: if history {
+                InterestMode::CurrentFuture
+            } else {
+                InterestMode::Future
+            },
             options: InterestOptions::KEYEXPRS + InterestOptions::TOKENS,
             wire_expr: Some(key_expr.to_wire(self).to_owned()),
             ext_qos: declare::ext::QoSType::DECLARE,