From a01e21663fc632d560c42d5e996824a89ea26e23 Mon Sep 17 00:00:00 2001
From: Juergen Kunz <juergen@foss.global>
Date: Mon, 23 Mar 2026 14:51:14 +0000
Subject: [PATCH] fix(prometheus): clean up default Prometheus metric
 collectors on stop

---
 changelog.md                            |  6 +++++
 ts/00_commitinfo_data.ts                |  2 +-
 ts/smartmetrics.classes.smartmetrics.ts |  7 +++++-
 ts/smartmetrics.prom.ts                 | 32 ++++++++++++++++++++-----
 4 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/changelog.md b/changelog.md
index cfffa4d..91d375b 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## 2026-03-23 - 3.0.3 - fix(prometheus)
+clean up default Prometheus metric collectors on stop
+
+- Return cleanup handlers from default metric registration for event loop and GC observers.
+- Dispose registered Prometheus default metric collectors when stopping Smartmetrics to prevent lingering observers.
+
 ## 2026-03-02 - 3.0.2 - fix(pidusage)
 prune history entries for PIDs not present in the requested set to avoid stale data and memory growth
 
diff --git a/ts/00_commitinfo_data.ts b/ts/00_commitinfo_data.ts
index c627098..fa13cad 100644
--- a/ts/00_commitinfo_data.ts
+++ b/ts/00_commitinfo_data.ts
@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartmetrics',
-  version: '3.0.2',
+  version: '3.0.3',
   description: 'A package for easy collection and reporting of system and process metrics.'
 }
diff --git a/ts/smartmetrics.classes.smartmetrics.ts b/ts/smartmetrics.classes.smartmetrics.ts
index b69b94e..e99efa1 100644
--- a/ts/smartmetrics.classes.smartmetrics.ts
+++ b/ts/smartmetrics.classes.smartmetrics.ts
@@ -22,10 +22,11 @@ export class SmartMetrics {
   // HTTP server for Prometheus endpoint
   private prometheusServer?: plugins.http.Server;
   private prometheusPort?: number;
+  private cleanupDefaultMetrics?: () => void;
 
   public setup() {
     this.registry = new plugins.prom.Registry();
-    plugins.prom.collectDefaultMetrics(this.registry);
+    this.cleanupDefaultMetrics = plugins.prom.collectDefaultMetrics(this.registry);
 
     // Initialize custom gauges
     this.cpuPercentageGauge = new plugins.prom.Gauge({
@@ -295,5 +296,9 @@ export class SmartMetrics {
   public stop() {
     this.started = false;
     this.disablePrometheusEndpoint();
+    if (this.cleanupDefaultMetrics) {
+      this.cleanupDefaultMetrics();
+      this.cleanupDefaultMetrics = undefined;
+    }
   }
 }
diff --git a/ts/smartmetrics.prom.ts b/ts/smartmetrics.prom.ts
index 09d5fd4..3411360 100644
--- a/ts/smartmetrics.prom.ts
+++ b/ts/smartmetrics.prom.ts
@@ -288,20 +288,25 @@ export class Histogram implements IMetric {
 
 // ── Default Metrics Collectors ──────────────────────────────────────────────
 
-export function collectDefaultMetrics(registry: Registry): void {
+export function collectDefaultMetrics(registry: Registry): () => void {
   registerProcessCpuTotal(registry);
   registerProcessStartTime(registry);
   registerProcessMemory(registry);
   registerProcessOpenFds(registry);
   registerProcessMaxFds(registry);
-  registerEventLoopLag(registry);
+  const cleanupEventLoop = registerEventLoopLag(registry);
   registerProcessHandles(registry);
   registerProcessRequests(registry);
   registerProcessResources(registry);
   registerHeapSizeAndUsed(registry);
   registerHeapSpaces(registry);
   registerVersion(registry);
-  registerGc(registry);
+  const cleanupGc = registerGc(registry);
+
+  return () => {
+    cleanupEventLoop();
+    cleanupGc();
+  };
 }
 
 function registerProcessCpuTotal(registry: Registry): void {
@@ -420,7 +425,7 @@ function registerProcessMaxFds(registry: Registry): void {
   });
 }
 
-function registerEventLoopLag(registry: Registry): void {
+function registerEventLoopLag(registry: Registry): () => void {
   let histogram: ReturnType<typeof monitorEventLoopDelay> | null = null;
   try {
     histogram = monitorEventLoopDelay({ resolution: 10 });
@@ -496,6 +501,13 @@ function registerEventLoopLag(registry: Registry): void {
       },
     });
   }
+
+  return () => {
+    if (histogram) {
+      histogram.disable();
+      histogram = null;
+    }
+  };
 }
 
 function registerProcessHandles(registry: Registry): void {
@@ -632,7 +644,7 @@ function registerVersion(registry: Registry): void {
   });
 }
 
-function registerGc(registry: Registry): void {
+function registerGc(registry: Registry): () => void {
   const gcHistogram = new Histogram({
     name: 'nodejs_gc_duration_seconds',
     help: 'Garbage collection duration by kind, in seconds.',
@@ -649,8 +661,9 @@ function registerGc(registry: Registry): void {
     15: 'All',
   };
 
+  let obs: PerformanceObserver | null = null;
   try {
-    const obs = new PerformanceObserver((list) => {
+    obs = new PerformanceObserver((list) => {
       for (const entry of list.getEntries()) {
         const gcEntry = entry as any;
         const kind = kindLabels[gcEntry.detail?.kind ?? gcEntry.kind] || 'Unknown';
@@ -661,6 +674,13 @@ function registerGc(registry: Registry): void {
   } catch {
     // GC observation not available
   }
+
+  return () => {
+    if (obs) {
+      obs.disconnect();
+      obs = null;
+    }
+  };
 }
 
 // ── Helpers ─────────────────────────────────────────────────────────────────