Merge pull request #78 from jszafran/add_s3_fallback_on_app_startup

Use S3 as fallback source upon application startup.

backend/cmd/api/main.go

@@ -52,7 +52,18 @@ func initializeDataSnapshot() (eurostat.DataSnapshot, error) {
 	case "production":
 		log.Println("DEPLOY_ENV=production; reading live snapshot from Eurostat.")
 		snapshot, err = eurostat.DataSnapshotFromEurostat()
-		if err != nil {
+		if err != nil && os.Getenv("USE_S3_AS_FALLBACK") == "true" {
+			log.Printf("Reading live snapshot from Eurostat failed because of: %s\n", err)
+			sm, err := eurostat.NewSnapshotManager(os.Getenv("S3_BUCKET"))
+			if err != nil {
+				return snapshot, err
+			}
+
+			snapshot, err = sm.LatestSnapshotFromS3()
+			if err != nil {
+				return snapshot, err
+			}
+		} else {
 			return snapshot, err
 		}
 	}

backend/cmd/api/models.go

@@ -15,7 +15,7 @@ type WeeklyDeathsResponse struct {
 	WeeklyDeaths []eurostat.WeekYearDeaths `json:"weekly_deaths"`
 }
 
-// MetadataLabel is a represenation of label data
+// MetadataLabel is a representation of label data
 // that is returned by /api/labels endpoint.
 type MetadataLabel struct {
 	Value string `json:"value"`

backend/fly.toml

@@ -13,6 +13,7 @@ primary_region = "cdg"
   PORT = "8080"
   PRIMARY_REGION = "cdg"
   S3_BUCKET = "eurostat-weekly-deaths-snapshots"
+  USE_S3_AS_FALLBACK = "true"
 
 [[services]]
   protocol = "tcp"

backend/internal/eurostat/snapshots.go

@@ -140,6 +140,8 @@ func latestKey(keys []string) (string, error) {
 
 func (sm *SnapshotManager) LatestSnapshotFromS3() (DataSnapshot, error) {
 	var ds DataSnapshot
+
+	log.Println("Attempting to fetch latest snapshot from S3.")
 	obj := make([]string, 0)
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
 	defer cancel()
@@ -169,6 +171,6 @@ func (sm *SnapshotManager) LatestSnapshotFromS3() (DataSnapshot, error) {
 	if err != nil {
 		return ds, err
 	}
-
+	log.Printf("Successfully fetched S3 snapshot (timestamp: %s)\n", ds.Timestamp)
 	return ds, nil
 }