Add system uptime metric

.chloggen/add-system-uptime.yaml

@@ -0,0 +1,17 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the area of concern in the attributes-registry, (e.g. http, cloud, db)
+component: system
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add system uptime metric
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+# The values here must be integers.
+issues: [648]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

docs/system/system-metrics.md

@@ -1159,3 +1159,22 @@ See also the [Slab allocator](https://blogs.oracle.com/linux/post/understanding-
 <!-- prettier-ignore-end -->
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 <!-- endsemconv -->
+
+### Metric: `system.uptime`
+
+This metric is [recommended][MetricRecommended].
+
+<!-- semconv metric.system.uptime -->
+<!-- NOTE: THIS TEXT IS AUTOGENERATED. DO NOT EDIT BY HAND. -->
+<!-- see templates/registry/markdown/snippet.md.j2 -->
+<!-- prettier-ignore-start -->
+<!-- markdownlint-capture -->
+<!-- markdownlint-disable -->
+
+| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
+| -------- | --------------- | ----------- | -------------- | --------- |
+| `system.uptime` | Counter | `s` | The time the system has been running | ![Experimental](https://img.shields.io/badge/-experimental-blue) |
+
+<!-- markdownlint-restore -->
+<!-- prettier-ignore-end -->
+<!-- END AUTOGENERATED TEXT -->

model/system/metrics.yaml

@@ -394,3 +394,13 @@ groups:
     unit: "By"
     attributes:
       - ref: linux.memory.slab.state
+
+  # system.uptime metric
+  - id: metric.system.uptime
+    type: metric
+    metric_name: system.uptime
+    stability: experimental
+    brief: "The time the system has been running"
+    instrument: counter
+    unit: "s"
+    attributes: []