pkg/otlp/metrics: fix otel.* namespaced metrics

.chloggen/gbbr_fix-otel-namespace.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component (e.g. pkg/quantile)
+component: pkg/otlp
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: System (and process.*) metrics were remapped with otel.*, overwriting the original metric and losing it. This change fixes that, keeping the original metric.
+
+# The PR related to this change
+issues: [141]
+
+# (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:

pkg/otlp/metrics/metrics_remapping.go

@@ -69,7 +69,12 @@ func remapSystemMetrics(all pmetric.MetricSlice, m pmetric.Metric) {
 	case "system.filesystem.utilization":
 		copyMetric(all, m, "system.disk.in_use", 1)
 	}
-	// process.* and system.* metrics need to be prepended with the otel.* namespace
+	if strings.HasPrefix(name, "system.") {
+		// we keep the original metric for system.* metrics
+		newm := all.AppendEmpty()
+		m.CopyTo(newm)
+	}
+	// and we prepend all of them with the otel.* namespace namespace
 	m.SetName("otel." + m.Name())
 }
 

pkg/otlp/metrics/metrics_remapping_test.go

@@ -275,16 +275,27 @@ func TestRemapMetrics(t *testing.T) {
 			out: []pmetric.Metric{metric("container.net.rcvd.packets", point{f: 15})},
 		},
 	} {
-		lena := dest.Len()
-		checkprefix := strings.HasPrefix(tt.in.Name(), "system.") || strings.HasPrefix(tt.in.Name(), "process.")
-		remapMetrics(dest, tt.in)
-		if checkprefix {
-			require.True(t, strings.HasPrefix(tt.in.Name(), "otel."), "system.* and process.* metrics need to be prepended with the otel.* namespace")
-		}
-		require.Equal(t, dest.Len()-lena, len(tt.out), "unexpected number of metrics added")
-		for i, out := range tt.out {
-			require.Equal(t, out, dest.At(dest.Len()-len(tt.out)+i))
-		}
+		t.Run("", func(t *testing.T) {
+			lenin := dest.Len()
+			issystem := strings.HasPrefix(tt.in.Name(), "system.")
+			out := tt.out
+			if issystem {
+				// the original system.* metrics need to be preserved
+				newm := pmetric.NewMetric()
+				tt.in.CopyTo(newm)
+				out = append(out, newm)
+			}
+			isprocess := strings.HasPrefix(tt.in.Name(), "process.")
+			remapMetrics(dest, tt.in)
+			if issystem || isprocess {
+				// system.* and process.* metrics have been prepended with the otel.* namespace
+				require.True(t, strings.HasPrefix(tt.in.Name(), "otel."), "system.* and process.* metrics need to be prepended with the otel.* namespace")
+			}
+			require.Equal(t, dest.Len()-lenin, len(out), "unexpected number of metrics added")
+			for i, o := range out {
+				require.Equal(t, o, dest.At(dest.Len()-len(out)+i))
+			}
+		})
 	}
 
 }