Auto detect GCE, GKE and AWS EC2 resources (#312)

* add gcp resource

* fix review comments

Author: mayurkale22

packages/opencensus-resource-util/package-lock.json

@@ -6,6 +6,8 @@
   "types": "build/src/index.d.ts",
   "repository": "census-instrumentation/opencensus-node",
   "scripts": {
+    "test": "nyc mocha build/test/**/*.js",
+    "codecov": "nyc report --reporter=json && codecov -f coverage/*.json",
     "clean": "rimraf build/*",
     "check": "gts check",
     "compile": "tsc -p .",
@@ -44,6 +46,7 @@
     "gts": "^0.9.0",
     "mocha": "^5.1.1",
     "nyc": "^13.0.0",
+    "nock": "^10.0.0",
     "rimraf": "^2.6.2",
     "typescript": "~3.2.0"
   },

packages/opencensus-resource-util/package.json

@@ -0,0 +1,38 @@
+/**
+ * Copyright 2019, OpenCensus 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.
+ */
+
+import {CoreResource, Resource} from '@opencensus/core';
+import {getAwsEC2Resource, getComputerEngineResource, getKubernetesEngineResource, getResourceType, ResourceType} from './resource-utils';
+
+/**
+ * Returns a Resource. Detector sequentially runs resource detection from
+ * environment variables, K8S, GCE and AWS.
+ */
+export async function detectResource(): Promise<Resource> {
+  const resources = [CoreResource.createFromEnvironmentVariables()];
+
+  const resourceType = await getResourceType();
+  if (resourceType === ResourceType.GCP_GKE_CONTAINER) {
+    resources.push(await getKubernetesEngineResource());
+  } else if (resourceType === ResourceType.GCP_GCE_INSTANCE) {
+    resources.push(await getComputerEngineResource());
+  }
+  if (resourceType === ResourceType.AWS_EC2_INSTANCE) {
+    resources.push(await getAwsEC2Resource());
+  }
+
+  return CoreResource.mergeResources(resources);
+}

packages/opencensus-resource-util/src/detect-resource.ts

@@ -13,3 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
+export * from './resource-labels';
+export * from './detect-resource';