Added google cloud function resource detector (#1584)

* adding cloud function detector

* linting changes

* changed a function name

* using cloudrun implementation for getting projectID and region
return nil,nil when not on cloud-function

* using provided context

* adding unit test cases

* ran make pre-commit

* incorporated review comment

* incorporating review comments.

* added changelog

* Making cloudFunction struct private

* incorporating review comments

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -13,6 +13,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - DynamoDB spans created with the `go.opentelemetry.io/contrib/instrumentation/github.com/aws/aws-sdk-go-v2/otelaws` package will now have the appropriate database attributes added for the operation being performed.
   These attributes are detected automatically, but it is also now possible to provide a custom function to set attributes using `WithAttributeSetter`. (#1582)
+- Add resource detector for GCP cloud function.
 
 ### Fixed
 

detectors/gcp/cloud-function.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"
+	"os"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/resource"
+	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
+)
+
+const (
+	gcpFunctionNameKey = "K_SERVICE"
+)
+
+// NewCloudFunction will return a GCP Cloud Function resource detector.
+func NewCloudFunction() resource.Detector {
+	return &cloudFunction{
+		cloudRun: NewCloudRun(),
+	}
+}
+
+// cloudFunction collects resource information of GCP Cloud Function
+type cloudFunction struct {
+	cloudRun *CloudRun
+}
+
+// Detect detects associated resources when running in GCP Cloud Function.
+func (f *cloudFunction) Detect(ctx context.Context) (*resource.Resource, error) {
+	functionName, ok := f.googleCloudFunctionName()
+	if !ok {
+		return nil, nil
+	}
+
+	projectID, err := f.cloudRun.mc.ProjectID()
+	if err != nil {
+		return nil, err
+	}
+	region, err := f.cloudRun.cloudRegion(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	attributes := []attribute.KeyValue{
+		semconv.CloudProviderGCP,
+		semconv.CloudPlatformGCPCloudFunctions,
+		semconv.FaaSNameKey.String(functionName),
+		semconv.CloudAccountIDKey.String(projectID),
+		semconv.CloudRegionKey.String(region),
+	}
+	return resource.NewWithAttributes(semconv.SchemaURL, attributes...), nil
+
+}
+
+func (f *cloudFunction) googleCloudFunctionName() (string, bool) {
+	return os.LookupEnv(gcpFunctionNameKey)
+}

detectors/gcp/cloud-function_test.go

@@ -0,0 +1,175 @@
+// 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"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/resource"
+	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
+)
+
+var (
+	errTest = errors.New("testError")
+)
+
+const (
+	projectIDValue = "some-projectID"
+	regionValue    = "some-region"
+	functionName   = "sample-function"
+)
+
+type metaDataClientImpl struct {
+	projectID  func() (string, error)
+	get        func(string) (string, error)
+	instanceID func() (string, error)
+}
+
+func (mock *metaDataClientImpl) ProjectID() (string, error) {
+	if mock.projectID != nil {
+		return mock.projectID()
+	}
+	return "", nil
+}
+
+func (mock *metaDataClientImpl) Get(key string) (string, error) {
+	if mock.get != nil {
+		return mock.get(key)
+	}
+	return "", nil
+}
+
+func (mock *metaDataClientImpl) InstanceID() (string, error) {
+	if mock.instanceID != nil {
+		return mock.instanceID()
+	}
+	return "", nil
+}
+
+type want struct {
+	res *resource.Resource
+	err error
+}
+
+func TestCloudFunctionDetect(t *testing.T) {
+	oldValue, ok := os.LookupEnv(gcpFunctionNameKey)
+	if !ok {
+		err := os.Setenv(gcpFunctionNameKey, functionName)
+		if err != nil {
+			t.Error("unable to set environment variable ", err)
+		}
+	}
+	defer func() {
+		if !ok {
+			os.Unsetenv(gcpFunctionNameKey)
+		} else {
+			os.Setenv(gcpFunctionNameKey, oldValue)
+		}
+	}()
+	tests := []struct {
+		name     string
+		cr       *CloudRun
+		expected want
+	}{
+		{
+			name: "error in reading ProjectID",
+			cr: &CloudRun{
+				mc: &metaDataClientImpl{
+					projectID: func() (string, error) {
+						return "", errTest
+					},
+				},
+			},
+			expected: want{
+				res: nil,
+				err: errTest,
+			},
+		},
+		{
+			name: "error in reading region",
+			cr: &CloudRun{
+				mc: &metaDataClientImpl{
+					get: func(key string) (string, error) {
+						return "", errTest
+					},
+				},
+			},
+			expected: want{
+				res: nil,
+				err: errTest,
+			},
+		},
+		{
+			name: "success",
+			cr: &CloudRun{
+				mc: &metaDataClientImpl{
+					projectID: func() (string, error) {
+						return projectIDValue, nil
+					},
+					get: func(key string) (string, error) {
+						return regionValue, nil
+					},
+				},
+			},
+			expected: want{
+				res: resource.NewSchemaless([]attribute.KeyValue{
+					semconv.CloudProviderGCP,
+					semconv.CloudPlatformGCPCloudFunctions,
+					semconv.FaaSNameKey.String(functionName),
+					semconv.CloudAccountIDKey.String(projectIDValue),
+					semconv.CloudRegionKey.String(regionValue),
+				}...),
+				err: nil,
+			},
+		},
+	}
+
+	for _, test := range tests {
+		detector := cloudFunction{
+			cloudRun: test.cr,
+		}
+		res, err := detector.Detect(context.Background())
+		if err != test.expected.err {
+			t.Fatalf("got unexpected failure: %v", err)
+		} else if diff := cmp.Diff(test.expected.res, res); diff != "" {
+			t.Errorf("detected resource differ from expected (-want, +got)\n%s", diff)
+		}
+	}
+}
+
+func TestNotOnCloudFunction(t *testing.T) {
+	oldValue, ok := os.LookupEnv(gcpFunctionNameKey)
+	if ok {
+		os.Unsetenv(gcpFunctionNameKey)
+	}
+	defer func() {
+		if ok {
+			os.Setenv(gcpFunctionNameKey, oldValue)
+		}
+	}()
+	detector := NewCloudFunction()
+	res, err := detector.Detect(context.Background())
+	if err != nil {
+		t.Errorf("expected cloud function detector to return error as nil, but returned %v", err)
+	} else if res != nil {
+		t.Errorf("expected cloud function detector to return resource as nil, but returned %v", res)
+	}
+}