Resource API (open-telemetry#59)

* Resource: Add merge function

* Add merge operation on Resource

* use shorthand syntax

packages/opentelemetry-core/package.json

@@ -49,5 +49,7 @@
     "ts-node": "^8.0.0",
     "typescript": "^3.4.5"
   },
-  "dependencies": {}
+  "dependencies": {
+    "@opentelemetry/types": "^0.0.1"
+  }
 }

packages/opentelemetry-core/src/index.ts

@@ -13,3 +13,5 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
+export * from './resources/Resource';

packages/opentelemetry-core/src/resources/Resource.ts

@@ -0,0 +1,32 @@
+/**
+ * Copyright 2019, 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
+ *
+ *      https://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.
+ */
+
+import * as types from '@opentelemetry/types';
+
+export class Resource implements types.Resource {
+  constructor(
+    // TODO: Consider to add check/validation on labels.
+    readonly labels: { [key: string]: string }
+  ) {}
+
+  merge(other: types.Resource | null): types.Resource {
+    if (!other || !Object.keys(other.labels).length) return this;
+
+    // Labels from resource overwrite labels from other resource.
+    const mergedLabels = Object.assign({}, other.labels, this.labels);
+    return new Resource(mergedLabels);
+  }
+}

packages/opentelemetry-core/test/resource.test.ts

@@ -0,0 +1,78 @@
+/**
+ * Copyright 2019, 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
+ *
+ *      https://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.
+ */
+
+import * as assert from 'assert';
+import { Resource } from '../src/resources/Resource';
+
+describe('Resource', () => {
+  const resource1 = new Resource({
+    'k8s.io/container/name': 'c1',
+    'k8s.io/namespace/name': 'default',
+    'k8s.io/pod/name': 'pod-xyz-123',
+  });
+  const resource2 = new Resource({
+    'k8s.io/zone': 'zone1',
+    'k8s.io/location': 'location',
+  });
+  const resource3 = new Resource({
+    'k8s.io/container/name': 'c2',
+    'k8s.io/location': 'location1',
+  });
+  const emptyResource = new Resource({});
+
+  it('should return merged resource', () => {
+    const expectedResource = new Resource({
+      'k8s.io/container/name': 'c1',
+      'k8s.io/namespace/name': 'default',
+      'k8s.io/pod/name': 'pod-xyz-123',
+      'k8s.io/zone': 'zone1',
+      'k8s.io/location': 'location',
+    });
+    const actualResource = resource1.merge(resource2);
+    assert.strictEqual(Object.keys(actualResource.labels).length, 5);
+    assert.deepStrictEqual(actualResource, expectedResource);
+  });
+
+  it('should return merged resource when collision in labels', () => {
+    const expectedResource = new Resource({
+      'k8s.io/container/name': 'c1',
+      'k8s.io/namespace/name': 'default',
+      'k8s.io/pod/name': 'pod-xyz-123',
+      'k8s.io/location': 'location1',
+    });
+    const actualResource = resource1.merge(resource3);
+    assert.strictEqual(Object.keys(actualResource.labels).length, 4);
+    assert.deepStrictEqual(actualResource, expectedResource);
+  });
+
+  it('should return merged resource when first resource is empty', () => {
+    const actualResource = emptyResource.merge(resource2);
+    assert.strictEqual(Object.keys(actualResource.labels).length, 2);
+    assert.deepStrictEqual(actualResource, resource2);
+  });
+
+  it('should return merged resource when other resource is empty', () => {
+    const actualResource = resource1.merge(emptyResource);
+    assert.strictEqual(Object.keys(actualResource.labels).length, 3);
+    assert.deepStrictEqual(actualResource, resource1);
+  });
+
+  it('should return merged resource when other resource is null', () => {
+    const actualResource = resource1.merge(null);
+    assert.strictEqual(Object.keys(actualResource.labels).length, 3);
+    assert.deepStrictEqual(actualResource, resource1);
+  });
+});

packages/opentelemetry-types/src/index.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+export * from './resources/Resource';
 export * from './trace/span';
 export * from './trace/span_context';
 export * from './trace/span_kind';

packages/opentelemetry-types/src/resources/Resource.ts

@@ -14,11 +14,24 @@
  * limitations under the License.
  */
 
-/** A Resource describes the entity for which a signal was collected. */
+/**
+ * A Resource describes the entity for which a signals (metrics or trace) are
+ * collected.
+ */
 export interface Resource {
   /**
    * A dictionary of labels with string keys and values that provide information
    * about the entity.
    */
   readonly labels: { [key: string]: string };
+
+  /**
+   * Returns a new, merged {@link Resource} by merging the current Resource
+   * with the other Resource. In case of a collision, current Resource takes
+   * precedence.
+   *
+   * @param other the Resource that will be merged with this.
+   * @returns the newly merged Resource.
+   */
+  merge(other: Resource | null): Resource;
 }