fix: guard against zero or negative DYN_HTTP_SVC_CONFIG_METRICS_POLL_INTERVAL_SECS

- Add validation to ensure poll interval is greater than 0
- Use filter() to reject zero or negative values
- Update documentation to clarify validation requirement
- Prevents potential issues with zero-duration polling intervals

Signed-off-by: Keiven Chang <keivenchang@users.noreply.github.com>

Author: keivenchang

lib/llm/src/http/service/metrics.rs

@@ -159,7 +159,7 @@ impl Metrics {
     /// ## Runtime Config Polling Configuration
     ///
     /// The polling behavior can be configured via environment variables:
-    /// - `DYN_HTTP_SVC_CONFIG_METRICS_POLL_INTERVAL_SECS`: Poll interval in seconds
+    /// - `DYN_HTTP_SVC_CONFIG_METRICS_POLL_INTERVAL_SECS`: Poll interval in seconds (must be > 0, defaults to 8)
     ///
     /// Metrics are never removed to preserve historical data. Runtime config and MDC
     /// metrics are updated when models are discovered and their configurations are available.

lib/llm/src/http/service/service_v2.rs

@@ -205,12 +205,12 @@ impl HttpService {
         tracing::info!(protocol, address, "Starting HTTP(S) service");
 
         // Start background task to poll runtime config metrics with proper cancellation
-        let poll_interval = Duration::from_secs(
-            std::env::var("DYN_HTTP_SVC_CONFIG_METRICS_POLL_INTERVAL_SECS")
-                .ok()
-                .and_then(|s| s.parse().ok())
-                .unwrap_or(8),
-        );
+        let poll_interval_secs = std::env::var("DYN_HTTP_SVC_CONFIG_METRICS_POLL_INTERVAL_SECS")
+            .ok()
+            .and_then(|s| s.parse::<u64>().ok())
+            .filter(|&secs| secs > 0) // Guard against zero or negative values
+            .unwrap_or(8);
+        let poll_interval = Duration::from_secs(poll_interval_secs);
 
         let _polling_task = super::metrics::Metrics::start_runtime_config_polling_task(
             self.state.metrics_clone(),