Add jvm.cpu.count metric (#52)

Co-authored-by: Armin Ruech <armin.ruech@dynatrace.com>

CHANGELOG.md

@@ -48,6 +48,8 @@ release.
 - Clarify that `http/dup` has higher precedence than `http` in case both values are present
   in `OTEL_SEMCONV_STABILITY_OPT_IN`
   ([#249](https://github.com/open-telemetry/semantic-conventions/pull/249))
+- Add `jvm.cpu.count` metric.
+  ([#52](https://github.com/open-telemetry/semantic-conventions/pull/52))
 
 ## v1.21.0 (2023-07-13)
 

docs/system/runtime-environment-metrics.md

@@ -30,6 +30,7 @@ semantic conventions when instrumenting runtime environments.
   * [Metric: `jvm.classes.unloaded`](#metric-jvmclassesunloaded)
   * [Metric: `jvm.classes.current_loaded`](#metric-jvmclassescurrent_loaded)
   * [Metric: `jvm.cpu.time`](#metric-jvmcputime)
+  * [Metric: `jvm.cpu.count`](#metric-jvmcpucount)
   * [Metric: `jvm.cpu.recent_utilization`](#metric-jvmcpurecent_utilization)
 - [JVM Metrics (Experimental)](#jvm-metrics-experimental)
   * [Metric: `jvm.memory.init`](#metric-jvmmemoryinit)
@@ -289,6 +290,21 @@ and [`com.ibm.lang.management.OperatingSystemMXBean#getProcessCpuTime()`](https:
 <!-- semconv metric.jvm.cpu.time(full) -->
 <!-- endsemconv -->
 
+### Metric: `jvm.cpu.count`
+
+This metric is [recommended][MetricRecommended].
+This metric is obtained from [`Runtime#availableProcessors()`](https://docs.oracle.com/javase/8/docs/api/java/lang/Runtime.html#availableProcessors--).
+Note that this is always an integer value (i.e. fractional or millicores are not represented).
+
+<!-- semconv metric.jvm.cpu.count(metric_table) -->
+| Name     | Instrument Type | Unit (UCUM) | Description    |
+| -------- | --------------- | ----------- | -------------- |
+| `jvm.cpu.count` | UpDownCounter | `{cpu}` | Number of processors available to the Java virtual machine. |
+<!-- endsemconv -->
+
+<!-- semconv metric.jvm.cpu.count(full) -->
+<!-- endsemconv -->
+
 ### Metric: `jvm.cpu.recent_utilization`
 
 This metric is [recommended][MetricRecommended].

model/metrics/process-runtime-jvm-metrics.yaml

@@ -114,6 +114,13 @@ groups:
     instrument: updowncounter
     unit: "{class}"
 
+  - id: metric.jvm.cpu.count
+    type: metric
+    metric_name: jvm.cpu.count
+    brief: "Number of processors available to the Java virtual machine."
+    instrument: updowncounter
+    unit: "{cpu}"
+
   - id: metric.jvm.cpu.time
     type: metric
     metric_name: jvm.cpu.time