add shutdown hook

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

docs/content/otel/jvm-runtime-metrics.md

@@ -93,7 +93,13 @@ OpenTelemetrySdk openTelemetry =
                 .build())
         .build();
 
-RuntimeMetrics.builder(openTelemetry).build();
+RuntimeMetrics runtimeMetrics =
+    RuntimeMetrics.builder(openTelemetry).build();
+
+// Close on shutdown to stop JMX metric collection
+Runtime.getRuntime()
+    .addShutdownHook(new Thread(runtimeMetrics::close));
+
 // Scrape at http://localhost:9464/metrics
 ```
 
@@ -134,7 +140,10 @@ OpenTelemetrySdk openTelemetry =
                 .build())
         .build();
 
-RuntimeMetrics.builder(openTelemetry).build();
+RuntimeMetrics runtimeMetrics =
+    RuntimeMetrics.builder(openTelemetry).build();
+Runtime.getRuntime()
+    .addShutdownHook(new Thread(runtimeMetrics::close));
 
 // Expose everything on one endpoint
 HTTPServer.builder()

examples/example-otel-jvm-runtime-metrics/src/main/java/io/prometheus/metrics/examples/otelruntimemetrics/Main.java

@@ -50,9 +50,13 @@ public static void main(String[] args) throws IOException, InterruptedException
     //    - captureGcCause() adds a jvm.gc.cause attribute to jvm.gc.duration
     //    - emitExperimentalTelemetry() enables buffer pools, extended CPU,
     //      extended memory pools, and file descriptor metrics
-    RuntimeMetrics.builder(openTelemetry).captureGcCause().emitExperimentalTelemetry().build();
+    RuntimeMetrics runtimeMetrics =
+        RuntimeMetrics.builder(openTelemetry).captureGcCause().emitExperimentalTelemetry().build();
 
-    // 5. Expose both Prometheus and OTel metrics on a single endpoint.
+    // 5. Close RuntimeMetrics on shutdown to stop JMX metric collection.
+    Runtime.getRuntime().addShutdownHook(new Thread(runtimeMetrics::close));
+
+    // 6. Expose both Prometheus and OTel metrics on a single endpoint.
     HTTPServer server = HTTPServer.builder().port(9400).registry(registry).buildAndStart();
 
     System.out.println(