Fix default merging of resource attributes from environment variable (#1785)

* updated controller to merge default resource with environment resource

* updated TracerProvider to merge default resource with environment resource

* Added Changelog entry

* Added resource.Environment(), modified resource.Default() for environment vairable and WithResource() configuration for TracerProvider and Controller

* Update CHANGELOG.md

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

* Moved environment detector to defaultResource initialization, added test cases

* Changes to default resource initialization

* made changes to the test cases

* added merging of resource with environment resource

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Added
 
+- - Extract resource attributes from the `OTEL_RESOURCE_ATTRIBUTES` environment variable and merge them with the `resource.Default` resource as well as resources provided to the `TracerProvider` and metric `Controller`. (#1785)
 - Added Jaeger Environment variables: `OTEL_EXPORTER_JAEGER_AGENT_HOST`, `OTEL_EXPORTER_JAEGER_AGENT_PORT`
   These environment variables can be used to override Jaeger agent hostname and port (#1752)
 - The OTLP exporter now has two new convenience functions, `NewExportPipeline` and `InstallNewPipeline`, setup and install the exporter in tracing and metrics pipelines. (#1373)

sdk/metric/controller/basic/config.go

@@ -64,9 +64,11 @@ type Option interface {
 	Apply(*Config)
 }
 
-// WithResource sets the Resource configuration option of a Config.
+// WithResource sets the Resource configuration option of a Config by merging it
+// with the Resource configuration in the environment.
 func WithResource(r *resource.Resource) Option {
-	return resourceOption{r}
+	res := resource.Merge(resource.Environment(), r)
+	return resourceOption{res}
 }
 
 type resourceOption struct{ *resource.Resource }

sdk/metric/controller/basic/controller_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/attribute"
+	ottest "go.opentelemetry.io/otel/internal/internaltest"
 	"go.opentelemetry.io/otel/metric"
 	export "go.opentelemetry.io/otel/sdk/export/metric"
 	"go.opentelemetry.io/otel/sdk/export/metric/aggregation"
@@ -34,6 +35,8 @@ import (
 	"go.opentelemetry.io/otel/sdk/resource"
 )
 
+const envVar = "OTEL_RESOURCE_ATTRIBUTES"
+
 func getMap(t *testing.T, cont *controller.Controller) map[string]float64 {
 	out := processortest.NewOutput(attribute.DefaultEncoder())
 
@@ -58,6 +61,12 @@ func checkTestContext(t *testing.T, ctx context.Context) {
 }
 
 func TestControllerUsesResource(t *testing.T) {
+	store, err := ottest.SetEnvVariables(map[string]string{
+		envVar: "key=value,T=U",
+	})
+	require.NoError(t, err)
+	defer func() { require.NoError(t, store.Restore()) }()
+
 	cases := []struct {
 		name    string
 		options []controller.Option
@@ -66,7 +75,7 @@ func TestControllerUsesResource(t *testing.T) {
 		{
 			name:    "explicitly empty resource",
 			options: []controller.Option{controller.WithResource(resource.Empty())},
-			wanted:  ""},
+			wanted:  resource.Environment().Encoded(attribute.DefaultEncoder())},
 		{
 			name:    "uses default if no resource option",
 			options: nil,
@@ -74,15 +83,18 @@ func TestControllerUsesResource(t *testing.T) {
 		{
 			name:    "explicit resource",
 			options: []controller.Option{controller.WithResource(resource.NewWithAttributes(attribute.String("R", "S")))},
-			wanted:  "R=S"},
+			wanted:  "R=S,T=U,key=value"},
 		{
 			name: "last resource wins",
 			options: []controller.Option{
 				controller.WithResource(resource.Default()),
 				controller.WithResource(resource.NewWithAttributes(attribute.String("R", "S"))),
 			},
-			wanted: "R=S",
-		},
+			wanted: "R=S,T=U,key=value"},
+		{
+			name:    "overlapping attributes with environment resource",
+			options: []controller.Option{controller.WithResource(resource.NewWithAttributes(attribute.String("T", "V")))},
+			wanted:  "T=V,key=value"},
 	}
 	for _, c := range cases {
 		t.Run(fmt.Sprintf("case-%s", c.name), func(t *testing.T) {

sdk/resource/resource.go

@@ -40,7 +40,7 @@ var (
 			otel.Handle(err)
 		}
 		return r
-	}(Detect(context.Background(), defaultServiceNameDetector{}, TelemetrySDK{}))
+	}(Detect(context.Background(), defaultServiceNameDetector{}, FromEnv{}, TelemetrySDK{}))
 )
 
 // NewWithAttributes creates a resource from attrs. If attrs contains
@@ -144,6 +144,17 @@ func Default() *Resource {
 	return defaultResource
 }
 
+// Environment returns an instance of Resource with attributes
+// extracted from the OTEL_RESOURCE_ATTRIBUTES environment variable.
+func Environment() *Resource {
+	detector := &FromEnv{}
+	resource, err := detector.Detect(context.Background())
+	if err == nil {
+		otel.Handle(err)
+	}
+	return resource
+}
+
 // Equivalent returns an object that can be compared for equality
 // between two resources.  This value is suitable for use as a key in
 // a map.

sdk/trace/provider.go

@@ -262,9 +262,7 @@ func WithSpanProcessor(sp SpanProcessor) TracerProviderOption {
 // resource.Default() Resource by default.
 func WithResource(r *resource.Resource) TracerProviderOption {
 	return func(opts *TracerProviderConfig) {
-		if r != nil {
-			opts.resource = r
-		}
+		opts.resource = resource.Merge(resource.Environment(), r)
 	}
 }
 

sdk/trace/trace_test.go

@@ -43,6 +43,8 @@ import (
 	"go.opentelemetry.io/otel/sdk/resource"
 )
 
+const envVar = "OTEL_RESOURCE_ATTRIBUTES"
+
 type storingHandler struct {
 	errs []error
 }
@@ -1203,6 +1205,12 @@ func TestWithSpanKind(t *testing.T) {
 }
 
 func TestWithResource(t *testing.T) {
+	store, err := ottest.SetEnvVariables(map[string]string{
+		envVar: "key=value,rk5=7",
+	})
+	require.NoError(t, err)
+	defer func() { require.NoError(t, store.Restore()) }()
+
 	cases := []struct {
 		name    string
 		options []TracerProviderOption
@@ -1212,7 +1220,7 @@ func TestWithResource(t *testing.T) {
 		{
 			name:    "explicitly empty resource",
 			options: []TracerProviderOption{WithResource(resource.Empty())},
-			want:    resource.Empty(),
+			want:    resource.Environment(),
 		},
 		{
 			name:    "uses default if no resource option",
@@ -1222,14 +1230,19 @@ func TestWithResource(t *testing.T) {
 		{
 			name:    "explicit resource",
 			options: []TracerProviderOption{WithResource(resource.NewWithAttributes(attribute.String("rk1", "rv1"), attribute.Int64("rk2", 5)))},
-			want:    resource.NewWithAttributes(attribute.String("rk1", "rv1"), attribute.Int64("rk2", 5)),
+			want:    resource.Merge(resource.Environment(), resource.NewWithAttributes(attribute.String("rk1", "rv1"), attribute.Int64("rk2", 5))),
 		},
 		{
 			name: "last resource wins",
 			options: []TracerProviderOption{
 				WithResource(resource.NewWithAttributes(attribute.String("rk1", "vk1"), attribute.Int64("rk2", 5))),
 				WithResource(resource.NewWithAttributes(attribute.String("rk3", "rv3"), attribute.Int64("rk4", 10)))},
-			want: resource.NewWithAttributes(attribute.String("rk3", "rv3"), attribute.Int64("rk4", 10)),
+			want: resource.Merge(resource.Environment(), resource.NewWithAttributes(attribute.String("rk3", "rv3"), attribute.Int64("rk4", 10))),
+		},
+		{
+			name:    "overlapping attributes with environment resource",
+			options: []TracerProviderOption{WithResource(resource.NewWithAttributes(attribute.String("rk1", "rv1"), attribute.Int64("rk5", 10)))},
+			want:    resource.Merge(resource.Environment(), resource.NewWithAttributes(attribute.String("rk1", "rv1"), attribute.Int64("rk5", 10))),
 		},
 	}
 	for _, tc := range cases {