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.

src/frontend/rpc.go

@@ -16,6 +16,7 @@ package main
 
 import (
 	"context"
+	"time"
 
 	pb "github.com/GoogleCloudPlatform/microservices-demo/src/frontend/genproto"
 
@@ -116,20 +117,11 @@ func (fe *frontendServer) getRecommendations(ctx context.Context, userID string,
 }
 
 func (fe *frontendServer) getAd(ctx context.Context) ([]*pb.Ad, error) {
-	return []*pb.Ad{
-		&pb.Ad{
-			Text:        "Try this OG insta camera from 1960s!",
-			RedirectUrl: "https://en.wikipedia.org/wiki/Instant_camera#Polaroid_cameras",
-		},
-		&pb.Ad{
-			Text:        "Check out the new instagrammy vacation destinations!",
-			RedirectUrl: "https://en.wikipedia.org/wiki/Italy",
-		},
-	}, nil
+	ctx, cancel := context.WithTimeout(ctx, time.Millisecond*100)
+	defer cancel()
 
-	// TODO(rghetia): uncomment below and revove the code above
-	// resp, err := pb.NewAdsServiceClient(fe.adSvcConn).GetAds(ctx, &pb.AdsRequest{
-	// 	ContextKeys: nil,
-	// })
-	// return resp.GetAds(), errors.Wrap(err, "failed to get ads")
+	resp, err := pb.NewAdServiceClient(fe.adSvcConn).GetAds(ctx, &pb.AdRequest{
+		ContextKeys: nil,
+	})
+	return resp.GetAds(), errors.Wrap(err, "failed to get ads")
 }