[processor/resourcedetection] Detect Azure Kubernetes Service cluster…

… name (open-telemetry#29328)

**Description:**

Added best effort support for detecting Azure Kubernetes Service cluster
name: `k8s.cluster.name`.

The cluster name can be extracted from the cluster's "resource group
name" which is retrieved using existing functionality. The
`parseClusterName` function has comments explaining the limitations.

**Link to tracking Issue:**

open-telemetry#26794

**Testing:**

I added unit tests for each scenario, and have tested against live AKS
clusters that fit each scenario. I am happy to spin these up if anyone
has any questions.

Added `k8s.cluster.name` to the list of AKS resource attributes.

.chloggen/resourcedetectionprocessor-azure-cluster-name.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: processor/resourcedetectionprocessor
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Detect Azure cluster name from IMDS metadata
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [26794]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

processor/resourcedetectionprocessor/README.md

@@ -400,6 +400,7 @@ processors:
 
   * cloud.provider ("azure")
   * cloud.platform ("azure_aks")
+  * k8s.cluster.name
 
 ```yaml
 processors:
@@ -409,6 +410,34 @@ processors:
     override: false
 ```
 
+#### Cluster Name
+
+Cluster name detection is disabled by default, and can be enabled with the
+following configuration:
+
+```yaml
+processors:
+  resourcedetection/aks:
+    detectors: [aks]
+    timeout: 2s
+    override: false
+    aks:
+      resource_attributes:
+        k8s.cluster.name: true
+```
+
+Azure AKS cluster name is derived from the Azure Instance Metadata Service's (IMDS) infrastructure resource group field. This field contains the resource group and name of the cluster, separated by underscores. e.g: `MC_<resource group>_<cluster name>_<location>`.
+
+Example:
+  - Resource group: my-resource-group
+  - Cluster name:   my-cluster
+  - Location:       eastus
+  - Generated name: MC_my-resource-group_my-cluster_eastus
+
+The cluster name is detected if it does not contain underscores and if a custom infrastructure resource group name was not used.
+
+If accurate parsing cannot be performed, the infrastructure resource group value is returned. This value can be used to uniquely identify the cluster, as Azure will not allow users to create multiple clusters with the same infrastructure resource group name.
+
 ### Consul
 
 Queries a [consul agent](https://www.consul.io/docs/agent) and reads its' [configuration endpoint](https://www.consul.io/api-docs/agent#read-configuration) to retrieve the following resource attributes:

processor/resourcedetectionprocessor/internal/azure/aks/aks.go

@@ -6,6 +6,7 @@ package aks // import "github.com/open-telemetry/opentelemetry-collector-contrib
 import (
 	"context"
 	"os"
+	"strings"
 
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/processor"
@@ -42,8 +43,9 @@ func (d *Detector) Detect(ctx context.Context) (resource pcommon.Resource, schem
 		return res, "", nil
 	}
 
+	m, err := d.provider.Metadata(ctx)
 	// If we can't get a response from the metadata endpoint, we're not running in Azure
-	if !azureMetadataAvailable(ctx, d.provider) {
+	if err != nil {
 		return res, "", nil
 	}
 
@@ -54,6 +56,9 @@ func (d *Detector) Detect(ctx context.Context) (resource pcommon.Resource, schem
 	if d.resourceAttributes.CloudPlatform.Enabled {
 		attrs.PutStr(conventions.AttributeCloudPlatform, conventions.AttributeCloudPlatformAzureAKS)
 	}
+	if d.resourceAttributes.K8sClusterName.Enabled {
+		attrs.PutStr(conventions.AttributeK8SClusterName, parseClusterName(m.ResourceGroupName))
+	}
 
 	return res, conventions.SchemaURL, nil
 }
@@ -62,7 +67,38 @@ func onK8s() bool {
 	return os.Getenv(kubernetesServiceHostEnvVar) != ""
 }
 
-func azureMetadataAvailable(ctx context.Context, p azure.Provider) bool {
-	_, err := p.Metadata(ctx)
-	return err == nil
+// parseClusterName parses the cluster name from the infrastructure
+// resource group name. AKS IMDS returns the resource group name in
+// the following formats:
+//
+// 1. Generated group: MC_<resource group>_<cluster name>_<location>
+//   - Example:
+//   - Resource group: my-resource-group
+//   - Cluster name:   my-cluster
+//   - Location:       eastus
+//   - Generated name: MC_my-resource-group_my-cluster_eastus
+//
+// 2. Custom group: custom-infra-resource-group-name
+//
+// When using the generated infrastructure resource group, the resource
+// group will include the cluster name. If the cluster's resource group
+// or cluster name contains underscores, parsing will fall back on the
+// unparsed infrastructure resource group name.
+//
+// When using a custom infrastructure resource group, the resource group name
+// does not contain the cluster name. The custom infrastructure resource group
+// name is returned instead.
+//
+// It is safe to use the infrastructure resource group name as a unique identifier
+// because Azure will not allow the user to create multiple AKS clusters with the same
+// infrastructure resource group name.
+func parseClusterName(resourceGroup string) string {
+	// Code inspired by https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/exporter/datadogexporter/internal/hostmetadata/internal/azure/provider.go#L36
+	splitAll := strings.Split(resourceGroup, "_")
+
+	if len(splitAll) == 4 && strings.ToLower(splitAll[0]) == "mc" {
+		return splitAll[len(splitAll)-2]
+	}
+
+	return resourceGroup
 }

processor/resourcedetectionprocessor/internal/azure/aks/aks_test.go

@@ -64,3 +64,52 @@ func mockProvider() *azure.MockProvider {
 	mp.On("Metadata").Return(&azure.ComputeMetadata{}, nil)
 	return mp
 }
+
+func TestParseClusterName(t *testing.T) {
+	cases := []struct {
+		name          string
+		resourceGroup string
+		expected      string
+	}{
+		{
+			name:          "Return cluster name",
+			resourceGroup: "MC_myResourceGroup_AKSCluster_eastus",
+			expected:      "AKSCluster",
+		},
+		{
+			name:          "Return resource group name, resource group contains underscores",
+			resourceGroup: "MC_Resource_Group_AKSCluster_eastus",
+			expected:      "MC_Resource_Group_AKSCluster_eastus",
+		},
+		{
+			name:          "Return resource group name, cluster name contains underscores",
+			resourceGroup: "MC_myResourceGroup_AKS_Cluster_eastus",
+			expected:      "MC_myResourceGroup_AKS_Cluster_eastus",
+		},
+		{
+			name:          "Custom infrastructure resource group name, return resource group name",
+			resourceGroup: "infra-group_name",
+			expected:      "infra-group_name",
+		},
+		{
+			name:          "Custom infrastructure resource group name with four underscores, return resource group name",
+			resourceGroup: "dev_infra_group_name",
+			expected:      "dev_infra_group_name",
+		},
+		// This case is unlikely because it would require the user to create
+		// a custom infrastructure resource group with the MC prefix and the
+		// correct number of underscores.
+		{
+			name:          "Custom infrastructure resource group name with MC prefix",
+			resourceGroup: "MC_group_name_location",
+			expected:      "name",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			actual := parseClusterName(tc.resourceGroup)
+			assert.Equal(t, tc.expected, actual)
+		})
+	}
+}

processor/resourcedetectionprocessor/internal/azure/aks/internal/metadata/testdata/config.yaml

@@ -5,9 +5,13 @@ all_set:
       enabled: true
     cloud.provider:
       enabled: true
+    k8s.cluster.name:
+      enabled: true
 none_set:
   resource_attributes:
     cloud.platform:
       enabled: false
     cloud.provider:
       enabled: false
+    k8s.cluster.name:
+      enabled: false

processor/resourcedetectionprocessor/internal/azure/aks/metadata.yaml

@@ -10,4 +10,8 @@ resource_attributes:
   cloud.platform:
     description: The cloud.platform
     type: string
-    enabled: true
+    enabled: true
+  k8s.cluster.name:
+    description: The k8s.cluster.name parsed from the Azure Instance Metadata Service's infrastructure resource group field
+    type: string
+    enabled: false