add resource type. (#528)

* add resource type.

* sort attributes in test to fix ci.

* add resource keys and update test.

sdk/resource/resource.go

@@ -0,0 +1,72 @@
+// Copyright 2020, 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 resource provides functionality for resource, which capture
+// identifying information about the entities for which signals are exported.
+package resource
+
+import (
+	"go.opentelemetry.io/otel/api/core"
+)
+
+// Resource describes an entity about which identifying information and metadata is exposed.
+type Resource struct {
+	labels map[core.Key]core.Value
+}
+
+// New creates a resource from a set of attributes.
+// If there are duplicates keys then the first value of the key is preserved.
+func New(kvs ...core.KeyValue) *Resource {
+	res := &Resource{
+		labels: map[core.Key]core.Value{},
+	}
+	for _, kv := range kvs {
+		if _, ok := res.labels[kv.Key]; !ok {
+			res.labels[kv.Key] = kv.Value
+		}
+	}
+	return res
+}
+
+// Merge creates a new resource by combining resource a and b.
+// If there are common key between resource a and b then value from resource a is preserved.
+// If one of the resources is nil then the other resource is returned without creating a new one.
+func Merge(a, b *Resource) *Resource {
+	if a == nil {
+		return b
+	}
+	if b == nil {
+		return a
+	}
+	res := &Resource{
+		labels: map[core.Key]core.Value{},
+	}
+	for k, v := range b.labels {
+		res.labels[k] = v
+	}
+	// labels from resource a overwrite labels from resource b.
+	for k, v := range a.labels {
+		res.labels[k] = v
+	}
+	return res
+}
+
+// Attributes returns a copy of attributes from the resource.
+func (r Resource) Attributes() []core.KeyValue {
+	attrs := make([]core.KeyValue, 0, len(r.labels))
+	for k, v := range r.labels {
+		attrs = append(attrs, core.KeyValue{Key: k, Value: v})
+	}
+	return attrs
+}

sdk/resource/resource_test.go

@@ -0,0 +1,126 @@
+// Copyright 2020, 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 resource_test
+
+import (
+	"fmt"
+	"sort"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+
+	"go.opentelemetry.io/otel/api/core"
+	"go.opentelemetry.io/otel/sdk/resource"
+)
+
+var (
+	kv11 = core.Key("k1").String("v11")
+	kv12 = core.Key("k1").String("v12")
+	kv21 = core.Key("k2").String("v21")
+	kv31 = core.Key("k3").String("v31")
+	kv41 = core.Key("k4").String("v41")
+)
+
+func TestNew(t *testing.T) {
+	cases := []struct {
+		name string
+		in   []core.KeyValue
+		want []core.KeyValue
+	}{
+		{
+			name: "New with common key order1",
+			in:   []core.KeyValue{kv11, kv12, kv21},
+			want: []core.KeyValue{kv11, kv21},
+		},
+		{
+			name: "New with common key order2",
+			in:   []core.KeyValue{kv12, kv11, kv21},
+			want: []core.KeyValue{kv12, kv21},
+		},
+		{
+			name: "New with nil",
+			in:   nil,
+			want: []core.KeyValue{},
+		},
+	}
+	for _, c := range cases {
+		t.Run(fmt.Sprintf("case-%s", c.name), func(t *testing.T) {
+			res := resource.New(c.in...)
+			if diff := cmp.Diff(
+				sortedAttributes(res.Attributes()),
+				sortedAttributes(c.want),
+				cmp.AllowUnexported(core.Value{})); diff != "" {
+				t.Fatalf("unwanted result: diff %+v,", diff)
+			}
+		})
+	}
+}
+
+func TestMerge(t *testing.T) {
+	cases := []struct {
+		name string
+		a, b *resource.Resource
+		want []core.KeyValue
+	}{
+		{
+			name: "Merge with no overlap, no nil",
+			a:    resource.New(kv11, kv31),
+			b:    resource.New(kv21, kv41),
+			want: []core.KeyValue{kv11, kv21, kv31, kv41},
+		},
+		{
+			name: "Merge with common key order1",
+			a:    resource.New(kv11),
+			b:    resource.New(kv12, kv21),
+			want: []core.KeyValue{kv21, kv11},
+		},
+		{
+			name: "Merge with common key order2",
+			a:    resource.New(kv12, kv21),
+			b:    resource.New(kv11),
+			want: []core.KeyValue{kv12, kv21},
+		},
+		{
+			name: "Merge with first resource nil",
+			a:    nil,
+			b:    resource.New(kv21),
+			want: []core.KeyValue{kv21},
+		},
+		{
+			name: "Merge with second resource nil",
+			a:    resource.New(kv11),
+			b:    nil,
+			want: []core.KeyValue{kv11},
+		},
+	}
+	for _, c := range cases {
+		t.Run(fmt.Sprintf("case-%s", c.name), func(t *testing.T) {
+			res := resource.Merge(c.a, c.b)
+			if diff := cmp.Diff(
+				sortedAttributes(res.Attributes()),
+				sortedAttributes(c.want),
+				cmp.AllowUnexported(core.Value{})); diff != "" {
+				t.Fatalf("unwanted result: diff %+v,", diff)
+			}
+		})
+	}
+}
+
+func sortedAttributes(attrs []core.KeyValue) []core.KeyValue {
+	sort.Slice(attrs[:], func(i, j int) bool {
+		return attrs[i].Key < attrs[j].Key
+	})
+	return attrs
+}

sdk/resource/resourcekeys/const.go

@@ -0,0 +1,80 @@
+// Copyright 2020, 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 resourcekeys contains well known type and label keys for resources.
+package resourcekeys // import "go.opentelemetry.io/otel/sdk/resource/resourcekeys"
+
+// Constants for Service resources.
+const (
+	// A uniquely identifying name for a Service.
+	ServiceKeyName       = "service.name"
+	ServiceKeyNamespace  = "service.namespace"
+	ServiceKeyInstanceID = "service.instance.id"
+	ServiceKeyVersion    = "service.version"
+)
+
+// Constants for Library resources.
+const (
+	// A uniquely identifying name for a Library.
+	LibraryKeyName     = "library.name"
+	LibraryKeyLanguage = "library.language"
+	LibraryKeyVersion  = "library.version"
+)
+
+// Constants for Kubernetes resources.
+const (
+	// A uniquely identifying name for the Kubernetes cluster. Kubernetes
+	// does not have cluster names as an internal concept so this may be
+	// set to any meaningful value within the environment. For example,
+	// GKE clusters have a name which can be used for this label.
+	K8SKeyClusterName    = "k8s.cluster.name"
+	K8SKeyNamespaceName  = "k8s.namespace.name"
+	K8SKeyPodName        = "k8s.pod.name"
+	K8SKeyDeploymentName = "k8s.deployment.name"
+)
+
+// Constants for Container resources.
+const (
+	// A uniquely identifying name for the Container.
+	ContainerKeyName      = "container.name"
+	ContainerKeyImageName = "container.image.name"
+	ContainerKeyImageTag  = "container.image.tag"
+)
+
+// Constants for Cloud resources.
+const (
+	CloudKeyProvider  = "cloud.provider"
+	CloudKeyAccountID = "cloud.account.id"
+	CloudKeyRegion    = "cloud.region"
+	CloudKeyZone      = "cloud.zone"
+
+	// Cloud Providers
+	CloudProviderAWS   = "aws"
+	CloudProviderGCP   = "gcp"
+	CloudProviderAZURE = "azure"
+)
+
+// Constants for Host resources.
+const (
+	// A uniquely identifying name for the host.
+	HostKeyName = "host.name"
+
+	// A hostname as returned by the 'hostname' command on host machine.
+	HostKeyHostName     = "host.hostname"
+	HostKeyID           = "host.id"
+	HostKeyType         = "host.type"
+	HostKeyImageName    = "host.image.name"
+	HostKeyImageID      = "host.image.id"
+	HostKeyImageVersion = "host.image.version"
+)