Add detector for Cloud Run service.

detectors/gcp/cloud-run.go

@@ -0,0 +1,86 @@
+// 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/label"
+	"go.opentelemetry.io/otel/sdk/resource"
+	"go.opentelemetry.io/otel/semconv"
+)
+
+// CloudRun collects resource information of Cloud Run instance.
+type CloudRun struct{}
+
+// compile time assertion that GCE implements the resource.Detector interface.
+var _ resource.Detector = (*CloudRun)(nil)
+
+// Detect detects associated resources when running on Cloud Run hosts.
+func (cloudrun *CloudRun) Detect(ctx context.Context) (*resource.Resource, error) {
+	// .OnGCE is actually testing whether the metadata server is available.
+	// Metadata server is supported on Cloud Run.
+	if !metadata.OnGCE() {
+		return nil, nil
+	}
+
+	labels := []label.KeyValue{
+		semconv.CloudProviderGCP,
+	}
+
+	var errInfo []string
+
+	if projectID, err := metadata.ProjectID(); hasProblem(err) {
+		errInfo = append(errInfo, err.Error())
+	} else if projectID != "" {
+		labels = append(labels, semconv.CloudAccountIDKey.String(projectID))
+	}
+
+	if region, err := metadata.Get("instance/region"); hasProblem(err) {
+		errInfo = append(errInfo, err.Error())
+	} else if region != "" {
+		labels = append(labels, semconv.CloudRegionKey.String(region))
+	}
+
+	if instanceID, err := metadata.InstanceID(); hasProblem(err) {
+		errInfo = append(errInfo, err.Error())
+	} else if instanceID != "" {
+		labels = append(labels, semconv.ServiceInstanceIDKey.String(instanceID))
+	}
+
+	// Part of Cloud Run container runtime contract.
+	// See https://cloud.google.com/run/docs/reference/container-contract
+	// The same K_SERVICE value ultimately maps to both `namespace` and
+	// `job` label of `generic_task` metric type.
+	if service := os.Getenv("K_SERVICE"); service == "" {
+		errInfo = append(errInfo, "envvar K_SERVICE contains empty string.")
+	} else {
+		labels = append(labels,
+			semconv.ServiceNamespaceKey.String(service),
+			semconv.ServiceNameKey.String(service),
+		)
+	}
+
+	var aggregatedErr error
+	if len(errInfo) > 0 {
+		aggregatedErr = fmt.Errorf("detecting Cloud Run resources: %s", errInfo)
+	}
+
+	return resource.New(labels...), aggregatedErr
+}