refactor: move uptime tracking from system_status_server(HTTP) to DRT level (#2587)

Co-authored-by: Keiven Chang <keivenchang@users.noreply.github.com>

Author: keivenchang

lib/runtime/src/distributed.rs

@@ -117,6 +117,13 @@ impl DistributedRuntime {
         });
         distributed_runtime.register_metrics_callback(drt_hierarchies, nats_client_callback);
 
+        // Initialize the uptime gauge in SystemHealth
+        distributed_runtime
+            .system_health
+            .lock()
+            .unwrap()
+            .initialize_uptime_gauge(&distributed_runtime)?;
+
         // Handle system status server initialization
         if let Some(cancel_token) = cancel_token {
             // System server is enabled - start both the state and HTTP server
@@ -153,17 +160,7 @@ impl DistributedRuntime {
                 }
             }
         } else {
-            // System server HTTP is disabled, but still create the state for metrics
-            // This ensures uptime_seconds metric is always registered
-            let system_status_state = crate::system_status_server::SystemStatusState::new(
-                Arc::new(distributed_runtime.clone()),
-            )?;
-
-            // Initialize the start time for uptime tracking
-            if let Err(e) = system_status_state.initialize_start_time() {
-                tracing::warn!("Failed to initialize system status start time: {}", e);
-            }
-
+            // System server HTTP is disabled, but uptime metrics are still being tracked via SystemHealth
             tracing::debug!(
                 "System status server HTTP endpoints disabled, but uptime metrics are being tracked"
             );
@@ -349,7 +346,7 @@ impl DistributedConfig {
 }
 
 #[cfg(test)]
-pub mod test_helpers {
+pub mod distributed_test_utils {
     //! Common test helper functions for DistributedRuntime tests
     // TODO: Use in-memory DistributedRuntime for tests instead of full runtime when available.
 
@@ -364,3 +361,61 @@ pub mod test_helpers {
             .unwrap()
     }
 }
+
+#[cfg(feature = "integration")]
+#[cfg(test)]
+mod tests {
+    use super::distributed_test_utils::create_test_drt_async;
+
+    #[tokio::test]
+    async fn test_drt_uptime_after_delay_system_disabled() {
+        // Test uptime with system status server disabled
+        temp_env::async_with_vars([("DYN_SYSTEM_ENABLED", Some("false"))], async {
+            // Start a DRT
+            let drt = create_test_drt_async().await;
+
+            // Wait 50ms
+            tokio::time::sleep(tokio::time::Duration::from_millis(50)).await;
+
+            // Check that uptime is 50+ ms
+            let uptime = drt.system_health.lock().unwrap().uptime();
+            assert!(
+                uptime >= std::time::Duration::from_millis(50),
+                "Expected uptime to be at least 50ms, but got {:?}",
+                uptime
+            );
+
+            println!(
+                "✓ DRT uptime test passed (system disabled): uptime = {:?}",
+                uptime
+            );
+        })
+        .await;
+    }
+
+    #[tokio::test]
+    async fn test_drt_uptime_after_delay_system_enabled() {
+        // Test uptime with system status server enabled
+        temp_env::async_with_vars([("DYN_SYSTEM_ENABLED", Some("true"))], async {
+            // Start a DRT
+            let drt = create_test_drt_async().await;
+
+            // Wait 50ms
+            tokio::time::sleep(tokio::time::Duration::from_millis(50)).await;
+
+            // Check that uptime is 50+ ms
+            let uptime = drt.system_health.lock().unwrap().uptime();
+            assert!(
+                uptime >= std::time::Duration::from_millis(50),
+                "Expected uptime to be at least 50ms, but got {:?}",
+                uptime
+            );
+
+            println!(
+                "✓ DRT uptime test passed (system enabled): uptime = {:?}",
+                uptime
+            );
+        })
+        .await;
+    }
+}

lib/runtime/src/lib.rs

@@ -21,6 +21,7 @@
 use std::{
     collections::HashMap,
     sync::{Arc, OnceLock, Weak},
+    time::Instant,
 };
 use tokio::sync::Mutex;
 
@@ -90,6 +91,8 @@ pub struct SystemHealth {
     use_endpoint_health_status: Vec<String>,
     health_path: String,
     live_path: String,
+    start_time: Instant,
+    uptime_gauge: OnceLock<prometheus::Gauge>,
 }
 
 impl SystemHealth {
@@ -109,6 +112,8 @@ impl SystemHealth {
             use_endpoint_health_status,
             health_path,
             live_path,
+            start_time: Instant::now(),
+            uptime_gauge: OnceLock::new(),
         }
     }
     pub fn set_health_status(&mut self, status: HealthStatus) {
@@ -145,6 +150,34 @@ impl SystemHealth {
 
         (healthy, endpoints)
     }
+
+    /// Initialize the uptime gauge using the provided metrics registry
+    pub fn initialize_uptime_gauge<T: crate::metrics::MetricsRegistry>(
+        &self,
+        registry: &T,
+    ) -> anyhow::Result<()> {
+        let gauge = registry.create_gauge(
+            "uptime_seconds",
+            "Total uptime of the DistributedRuntime in seconds",
+            &[],
+        )?;
+        self.uptime_gauge
+            .set(gauge)
+            .map_err(|_| anyhow::anyhow!("uptime_gauge already initialized"))?;
+        Ok(())
+    }
+
+    /// Get the current uptime as a Duration
+    pub fn uptime(&self) -> std::time::Duration {
+        self.start_time.elapsed()
+    }
+
+    /// Update the uptime gauge with the current uptime value
+    pub fn update_uptime_gauge(&self) {
+        if let Some(gauge) = self.uptime_gauge.get() {
+            gauge.set(self.uptime().as_secs_f64());
+        }
+    }
 }
 
 /// Type alias for runtime callback functions to reduce complexity

lib/runtime/src/metrics.rs

@@ -913,7 +913,7 @@ mod test_metricsregistry_units {
 #[cfg(test)]
 mod test_metricsregistry_prefixes {
     use super::*;
-    use crate::distributed::test_helpers::create_test_drt_async;
+    use crate::distributed::distributed_test_utils::create_test_drt_async;
     use prometheus::core::Collector;
 
     #[tokio::test]
@@ -1047,7 +1047,7 @@ mod test_metricsregistry_prometheus_fmt_outputs {
     use super::prometheus_names::{COMPONENT_NATS_METRICS, DRT_NATS_METRICS};
     use super::prometheus_names::{nats_client, nats_service};
     use super::*;
-    use crate::distributed::test_helpers::create_test_drt_async;
+    use crate::distributed::distributed_test_utils::create_test_drt_async;
     use prometheus::Counter;
     use std::sync::Arc;
 
@@ -1308,7 +1308,7 @@ mod test_metricsregistry_nats {
     use super::prometheus_names::{COMPONENT_NATS_METRICS, DRT_NATS_METRICS};
     use super::prometheus_names::{nats_client, nats_service};
     use super::*;
-    use crate::distributed::test_helpers::create_test_drt_async;
+    use crate::distributed::distributed_test_utils::create_test_drt_async;
     use crate::pipeline::PushRouter;
     use crate::{DistributedRuntime, Runtime};
     use tokio::time::{Duration, sleep};