fix(telemetry): schedule ExtendedHeartbeat on worker start

libdd-telemetry/src/worker/mod.rs

@@ -427,6 +427,11 @@ impl TelemetryWorker {
                     self.deadlines
                         .schedule_event(LifecycleAction::FlushData)
                         .unwrap();
+
+                    #[allow(clippy::unwrap_used)]
+                    self.deadlines
+                        .schedule_event(LifecycleAction::ExtendedHeartbeat)
+                        .unwrap();
                     self.data.started = true;
                 }
             }
@@ -494,15 +499,13 @@ impl TelemetryWorker {
                     Ok(()) => self.payload_sent_success(&extended_hb),
                     Err(err) => self.log_err(&err),
                 }
+                // Only re-schedule self. Resetting `FlushData` here would replace its
+                // existing deadline with `now + heartbeat_interval`, starving FlushData
+                // when `extended_heartbeat_interval < heartbeat_interval` because each
+                // ExtendedHeartbeat firing pushes FlushData out before it can fire.
                 #[allow(clippy::unwrap_used)]
                 self.deadlines
-                    .schedule_events(
-                        &mut [
-                            LifecycleAction::FlushData,
-                            LifecycleAction::ExtendedHeartbeat,
-                        ]
-                        .into_iter(),
-                    )
+                    .schedule_event(LifecycleAction::ExtendedHeartbeat)
                     .unwrap();
             }
             Lifecycle(Stop) => {
@@ -1283,7 +1286,10 @@ mod tests {
     use crate::worker::http_client::header::{
         DD_PARENT_SESSION_ID, DD_ROOT_SESSION_ID, DD_SESSION_ID,
     };
-    use crate::worker::{TelemetryWorker, TelemetryWorkerBuilder, TelemetryWorkerHandle};
+    use crate::worker::{
+        LifecycleAction, TelemetryActions, TelemetryWorker, TelemetryWorkerBuilder,
+        TelemetryWorkerFlavor, TelemetryWorkerHandle,
+    };
     use libdd_common::{http_common, Endpoint};
     use tokio::runtime::Runtime;
 
@@ -1436,6 +1442,111 @@ mod tests {
         );
     }
 
+    fn build_test_worker_with_flavor(flavor: TelemetryWorkerFlavor) -> TelemetryWorker {
+        let mut b = TelemetryWorkerBuilder::new(
+            "h".into(),
+            "svc".into(),
+            "lang".into(),
+            "1".into(),
+            "tv".into(),
+        );
+        b.config
+            .set_endpoint(Endpoint::from_slice("http://127.0.0.1:1"))
+            .unwrap();
+        b.runtime_id = Some("rid".into());
+        b.flavor = flavor;
+        b.build_worker(Some(tokio::runtime::Handle::current())).1
+    }
+
+    /// Every event with a delay must be scheduled on Start; otherwise it sits in
+    /// `delays` forever and its handler never fires. Walking `delays` (rather than
+    /// enumerating variants) guards against future periodic actions regressing.
+    #[tokio::test]
+    #[cfg_attr(miri, ignore)] // reqwest in dispatch_action
+    async fn full_flavor_start_schedules_every_periodic_action() {
+        let mut worker = build_test_worker_with_flavor(TelemetryWorkerFlavor::Full);
+
+        let _ = worker
+            .dispatch_action(TelemetryActions::Lifecycle(LifecycleAction::Start))
+            .await;
+
+        let delays: Vec<LifecycleAction> =
+            worker.deadlines.delays.iter().map(|(_, k)| *k).collect();
+        let scheduled: Vec<LifecycleAction> =
+            worker.deadlines.deadlines.iter().map(|(_, k)| *k).collect();
+
+        assert!(!delays.is_empty(), "scheduler should have periodic actions");
+        for ev in &delays {
+            assert!(
+                scheduled.contains(ev),
+                "{ev:?} has a delay but was not scheduled on Start; scheduled={scheduled:?}",
+            );
+        }
+    }
+
+    /// `MetricsLogs` flavor intentionally excludes lifecycle events. Negative guard
+    /// so any future change emitting them from this flavor has to update the test.
+    #[tokio::test]
+    #[cfg_attr(miri, ignore)] // reqwest in build_worker
+    async fn metrics_logs_flavor_start_does_not_schedule_extended_heartbeat() {
+        let mut worker = build_test_worker_with_flavor(TelemetryWorkerFlavor::MetricsLogs);
+
+        let _ = worker
+            .dispatch_metrics_logs_action(TelemetryActions::Lifecycle(LifecycleAction::Start))
+            .await;
+
+        let scheduled: Vec<LifecycleAction> =
+            worker.deadlines.deadlines.iter().map(|(_, k)| *k).collect();
+
+        assert!(scheduled.contains(&LifecycleAction::FlushMetricAggr));
+        assert!(scheduled.contains(&LifecycleAction::FlushData));
+        assert!(
+            !scheduled.contains(&LifecycleAction::ExtendedHeartbeat),
+            "MetricsLogs should not schedule ExtendedHeartbeat; scheduled={scheduled:?}",
+        );
+    }
+
+    /// Regression: when `extended_heartbeat_interval < heartbeat_interval`, the
+    /// ExtendedHeartbeat handler must not reset FlushData's deadline. If it did, each
+    /// firing would push FlushData to `now + heartbeat_interval` and the next
+    /// (sooner) ExtendedHeartbeat would push it again — starving FlushData forever.
+    #[tokio::test]
+    #[cfg_attr(miri, ignore)] // reqwest in dispatch_action
+    async fn extended_heartbeat_does_not_reset_flush_data() {
+        let mut worker = build_test_worker_with_flavor(TelemetryWorkerFlavor::Full);
+
+        let _ = worker
+            .dispatch_action(TelemetryActions::Lifecycle(LifecycleAction::Start))
+            .await;
+
+        let flush_data_before = worker
+            .deadlines
+            .deadlines
+            .iter()
+            .find(|(_, k)| *k == LifecycleAction::FlushData)
+            .map(|(d, _)| *d)
+            .expect("FlushData scheduled on Start");
+
+        let _ = worker
+            .dispatch_action(TelemetryActions::Lifecycle(
+                LifecycleAction::ExtendedHeartbeat,
+            ))
+            .await;
+
+        let flush_data_after = worker
+            .deadlines
+            .deadlines
+            .iter()
+            .find(|(_, k)| *k == LifecycleAction::FlushData)
+            .map(|(d, _)| *d)
+            .expect("FlushData should still be scheduled after ExtendedHeartbeat fires");
+
+        assert_eq!(
+            flush_data_before, flush_data_after,
+            "ExtendedHeartbeat must not reset FlushData's deadline",
+        );
+    }
+
     mod reset {
         use super::super::*;
         use crate::data::{