[processor/k8sattributes] Automatic resource attributes - annotation prefix (open-telemetry#38825)

This is the first part of
open-telemetry#37114
- the ability to use an annotation prefix to define a resource attribute

---------

Co-authored-by: Christos Markou <[email protected]>

Author: 2 people

.chloggen/operator-resource-attributes.yaml

@@ -0,0 +1,15 @@
+change_type: enhancement
+
+component: k8sattributesprocessor
+
+note: Add option to configure automatic resource attributes - with annotation prefix
+
+issues: [37114]
+
+subtext: |
+  Implements [Specify resource attributes using Kubernetes annotations](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/non-normative/k8s-attributes.md#specify-resource-attributes-using-kubernetes-annotations).
+  
+  If you are using the file log receiver, you can now create the same resource attributes as traces (via OTLP) received
+  from an application instrumented with the OpenTelemetry Operator -
+  simply by adding the `extract: { otel_annotations: true }` configuration to the `k8sattributesprocessor` processor.
+  See the [documentation](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/processor/k8sattributesprocessor/README.md#config-example) for more details.

processor/k8sattributesprocessor/README.md

@@ -251,6 +251,18 @@ extract:
       from: node
 ```
 
+## Configuring recommended resource attributes 
+
+The processor can be configured to set the 
+[recommended resource attributes](https://opentelemetry.io/docs/specs/semconv/non-normative/k8s-attributes/):
+
+- `otel_annotations` will translate `resource.opentelemetry.io/foo` to the `foo` resource attribute, etc.
+
+```yaml
+  extract:
+    otel_annotations: true 
+```
+
 ### Config example
 
 ```yaml
@@ -271,10 +283,11 @@ k8sattributes/2:
       - k8s.node.name
       - k8s.pod.start_time
     labels:
-     # This label extraction rule takes the value 'app.kubernetes.io/component' label and maps it to the 'app.label.component' attribute which will be added to the associated resources
-     - tag_name: app.label.component
-       key: app.kubernetes.io/component
-       from: pod
+      # This label extraction rule takes the value 'app.kubernetes.io/component' label and maps it to the 'app.label.component' attribute which will be added to the associated resources
+      - tag_name: app.label.component
+        key: app.kubernetes.io/component
+        from: pod
+    otel_annotations: true 
   pod_association:
     - sources:
         # This rule associates all resources containing the 'k8s.pod.ip' attribute with the matching pods. If this attribute is not present in the resource, this rule will not be able to find the matching pod.

processor/k8sattributesprocessor/config.go

@@ -166,6 +166,10 @@ type ExtractConfig struct {
 	// It is a list of FieldExtractConfig type. See FieldExtractConfig
 	// documentation for more details.
 	Labels []FieldExtractConfig `mapstructure:"labels"`
+
+	// OtelAnnotations extracts all pod annotations with the prefix "resource.opentelemetry.io" as resource attributes
+	// E.g. "resource.opentelemetry.io/foo" becomes "foo"
+	OtelAnnotations bool `mapstructure:"otel_annotations"`
 }
 
 // FieldExtractConfig allows specifying an extraction rule to extract a resource attribute from pod (or namespace)

processor/k8sattributesprocessor/factory.go

@@ -192,6 +192,7 @@ func createProcessorOpts(cfg component.Config) []option {
 	opts = append(opts, withExtractMetadata(oCfg.Extract.Metadata...))
 	opts = append(opts, withExtractLabels(oCfg.Extract.Labels...))
 	opts = append(opts, withExtractAnnotations(oCfg.Extract.Annotations...))
+	opts = append(opts, withOtelAnnotations(oCfg.Extract.OtelAnnotations))
 
 	// filters
 	opts = append(opts, withFilterNode(oCfg.Filter.Node, oCfg.Filter.NodeFromEnvVar))

processor/k8sattributesprocessor/options.go

@@ -198,6 +198,20 @@ func withExtractMetadata(fields ...string) option {
 	}
 }
 
+func withOtelAnnotations(enabled bool) option {
+	return func(p *kubernetesprocessor) error {
+		if enabled {
+			p.rules.Annotations = append(p.rules.Annotations, kube.FieldExtractionRule{
+				Name:                 "$1",
+				KeyRegex:             regexp.MustCompile(`^resource\.opentelemetry\.io/(.+)$`),
+				HasKeyRegexReference: true,
+				From:                 kube.MetadataFromPod,
+			})
+		}
+		return nil
+	}
+}
+
 // withExtractLabels allows specifying options to control extraction of pod labels.
 func withExtractLabels(labels ...FieldExtractConfig) option {
 	return func(p *kubernetesprocessor) error {

processor/k8sattributesprocessor/options_test.go

@@ -746,3 +746,36 @@ func TestWithExcludes(t *testing.T) {
 		})
 	}
 }
+
+func TestOtelAnnotations(t *testing.T) {
+	tests := []struct {
+		name            string
+		enabled         bool
+		wantAnnotations []kube.FieldExtractionRule
+	}{
+		{
+			name: "no automatic rules",
+		},
+		{
+			name:    "default automatic rules",
+			enabled: true,
+			wantAnnotations: []kube.FieldExtractionRule{
+				{
+					Name:                 "$1",
+					KeyRegex:             regexp.MustCompile(`^resource\.opentelemetry\.io/(.+)$`),
+					HasKeyRegexReference: true,
+					From:                 kube.MetadataFromPod,
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			p := kubernetesprocessor{}
+			rules := withOtelAnnotations(tt.enabled)
+			err := rules(&p)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.wantAnnotations, p.rules.Annotations)
+		})
+	}
+}