GKE detector (#154)

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Added
 
+- Create a detector that collects resources from GKE machines. (#139)
 - Create a detector that collects resources from GCE machines. (#132)
 - Add instrumentation for Kafka (github.com/Shopify/sarama). (#134)
 - Add links and status message for mock span. (#134)

detectors/gcp/gke.go

@@ -0,0 +1,71 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package gcp
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"cloud.google.com/go/compute/metadata"
+
+	"go.opentelemetry.io/otel/api/kv"
+	"go.opentelemetry.io/otel/api/standard"
+	"go.opentelemetry.io/otel/sdk/resource"
+)
+
+// GKE collects resource information of GKE computing instances
+type GKE struct{}
+
+// compile time assertion that GCE implements the resource.Detector interface.
+var _ resource.Detector = (*GKE)(nil)
+
+// Detect detects associated resources when running in GKE environment.
+func (gke *GKE) Detect(ctx context.Context) (*resource.Resource, error) {
+	gcpDetecor := GCE{}
+	gceLablRes, err := gcpDetecor.Detect(ctx)
+
+	if os.Getenv("KUBERNETES_SERVICE_HOST") == "" {
+		return gceLablRes, err
+	}
+
+	var errInfo []string
+	if err != nil {
+		errInfo = append(errInfo, err.Error())
+	}
+
+	labels := []kv.KeyValue{
+		standard.K8SNamespaceNameKey.String(os.Getenv("NAMESPACE")),
+		standard.K8SPodNameKey.String(os.Getenv("HOSTNAME")),
+	}
+
+	if containerName := os.Getenv("CONTAINER_NAME"); containerName != "" {
+		labels = append(labels, standard.ContainerNameKey.String(containerName))
+	}
+
+	if clusterName, err := metadata.InstanceAttributeValue("cluster-name"); hasProblem(err) {
+		errInfo = append(errInfo, err.Error())
+	} else if clusterName != "" {
+		labels = append(labels, standard.K8SClusterNameKey.String(clusterName))
+	}
+
+	k8sLabelRes := resource.New(labels...)
+	var aggregatedErr error
+	if len(errInfo) > 0 {
+		aggregatedErr = fmt.Errorf("detecting GKE resources: %s", errInfo)
+	}
+
+	return resource.Merge(gceLablRes, k8sLabelRes), aggregatedErr
+}