adding cloud function detector

Author: patil-kshitij

detectors/gcp/cloud-function.go

@@ -0,0 +1,99 @@
+// 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"
+	"errors"
+	"os"
+	"strings"
+
+	"cloud.google.com/go/compute/metadata"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/resource"
+	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
+)
+
+var (
+	errNotOnGoogleCloudFunction = errors.New("cannot detect environment variables from Google Cloud Function")
+)
+
+const (
+	gcpFunctionNameKey = "K_SERVICE"
+)
+
+//NewResourceDetector will return an implementation for gcp cloud function resource detector
+func NewResourceDetector() resource.Detector {
+	return &CloudFunction{
+		client: &gcpClientImpl{},
+	}
+}
+
+type gcpClient interface {
+	gcpProjectID() (string, error)
+	gcpRegion() (string, error)
+}
+type gcpClientImpl struct{}
+
+func (gi *gcpClientImpl) gcpProjectID() (string, error) {
+	return metadata.ProjectID()
+}
+
+func (gi *gcpClientImpl) gcpRegion() (string, error) {
+	var region string
+	zone, err := metadata.Zone()
+	if zone != "" {
+		splitArr := strings.SplitN(zone, "-", 3)
+		if len(splitArr) == 3 {
+			region = strings.Join(splitArr[0:2], "-")
+		}
+	}
+	return region, err
+}
+
+type CloudFunction struct {
+	client gcpClient
+}
+
+// Detect detects associated resources when running in  cloud function.
+func (f *CloudFunction) Detect(ctx context.Context) (*resource.Resource, error) {
+	functionName, ok := f.googleCloudFunctionName()
+	if !ok {
+		return nil, errNotOnGoogleCloudFunction
+	}
+
+	projectID, err := f.client.gcpProjectID()
+	if err != nil {
+		return nil, err
+	}
+	region, err := f.client.gcpRegion()
+	if err != nil {
+		return nil, err
+	}
+
+	attributes := []attribute.KeyValue{
+		semconv.CloudProviderGCP,
+		semconv.CloudPlatformGCPCloudFunctions,
+		attribute.String(string(semconv.FaaSNameKey), functionName),
+		semconv.CloudAccountIDKey.String(projectID),
+		semconv.CloudRegionKey.String(region),
+	}
+	return resource.NewSchemaless(attributes...), nil
+
+}
+
+func (f *CloudFunction) googleCloudFunctionName() (string, bool) {
+	return os.LookupEnv(gcpFunctionNameKey)
+}