Add system.cpu.total.norm.pct

Author: mamazzol

modules/apm/src/main/java/org/elasticsearch/telemetry/apm/internal/MetricValidator.java

@@ -69,6 +69,7 @@ public class MetricValidator {
         "es.thread_pool.security-crypto.*",
         "es.thread_pool.security-token-key.*",
         // APM Java agent-compatible metric names (see https://www.elastic.co/docs/reference/apm/agents/java/metrics#metrics-jvm)
+        "system.cpu.*",
         "system.memory.*",
         "system.process.*",
         "jvm.file_descriptor.*",

server/src/main/java/org/elasticsearch/monitor/metrics/SystemMetrics.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.monitor.jvm.SunThreadInfo;
 import org.elasticsearch.monitor.os.OsProbe;
 import org.elasticsearch.monitor.process.ProcessProbe;
+import org.elasticsearch.telemetry.metric.DoubleWithAttributes;
 import org.elasticsearch.telemetry.metric.LongWithAttributes;
 import org.elasticsearch.telemetry.metric.MeterRegistry;
 
@@ -49,6 +50,7 @@ protected void doStart() {
         registerSystemMemoryMetrics();
         registerCgroupMemoryMetrics();
         registerJvmGcMetrics();
+        registerSystemCpuMetrics();
     }
 
     @Override
@@ -177,6 +179,21 @@ private void registerJvmGcMetrics() {
         );
     }
 
+    private void registerSystemCpuMetrics() {
+        short initial = OsProbe.getSystemCpuPercent();
+        if (initial < 0) {
+            return;
+        }
+        metrics.add(
+            registry.registerDoubleGauge(
+                "system.cpu.total.norm.pct",
+                "System-wide CPU usage as a ratio.",
+                "1",
+                () -> new DoubleWithAttributes(Math.max(0, OsProbe.getSystemCpuPercent() / 100.0))
+            )
+        );
+    }
+
     private void registerLongGaugeUnlessNegative(String name, String description, String unit, LongSupplier supplier) {
         long initial = supplier.getAsLong();
         if (initial < 0) {