Initial commit for Ads Service. (#21)

* Initial commit for Ads Service.

* update comments for AdsService and AdsServiceClient

* Refactor Ads to Ad
Move building AdService to Docker
Use default setting for Stackdriver Exporter.
Add license text.

* Revert the projectId

- also remove commented code from frontend/rpc.go

* Add adservie to skaffold.yaml

* Remove skaffold-adservice.yaml

* Replace personal projectId with demo projectId.

* Fix the crash in adservice when ran in locally.

* Ignore .skaffold*yaml file and .kubernetes-manifests-*/ dir for easy ProjectID switch.

* Fixed review comments.
1. Changed Ad redirect urls to products.
2. Removed leftovers from Dockerfile/kub*manifests*yaml
3. Added retry for StackDriver.
4. Added log for Ad request.
5. Added comment for gradle caching.
6. Added README.md to src/adservice.

* Added GRPC Health service to Ad Service
Also added
1. timeout to getAd RPC call in frontend.
2. Async thread for stackdriver init.

kubernetes-manifests/adservice.yaml

@@ -0,0 +1,63 @@
+# Copyright 2018 Google LLC
+#
+# 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.
+
+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: adservice
+spec:
+  template:
+    metadata:
+      labels:
+        app: adservice
+    spec:
+      terminationGracePeriodSeconds: 5
+      containers:
+      - name: server
+        image: gcr.io/microservices-demo-app/adservice
+        ports:
+        - containerPort: 9555
+        env:
+        - name: PORT
+          value: "9555"
+        resources:
+          requests:
+            cpu: 200m
+            memory: 64Mi
+          limits:
+            cpu: 300m
+            memory: 128Mi
+        readinessProbe:
+          tcpSocket:
+            port: 9555
+          initialDelaySeconds: 5
+          periodSeconds: 10
+        livenessProbe:
+          tcpSocket:
+            port: 9555
+          initialDelaySeconds: 10
+          periodSeconds: 10
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: adservice
+spec:
+  type: ClusterIP
+  selector:
+    app: adservice
+  ports:
+  - name: grpc
+    port: 9555
+    targetPort: 9555