make

.gitignore

@@ -2,3 +2,4 @@
 /gtfs.zip
 /pretend-feed.bin
 /tmp/
+/bin

Makefile

@@ -1,3 +1,8 @@
+all: bin
+
+bin: cmd/main.go proto/*.go
+	go build -o bin cmd/main.go
+
 proto: proto/schema.pb.go proto/gtfs-realtime.pb.go
 
 proto/gtfs-realtime.pb.go: proto/gtfs-realtime.proto

cmd/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -10,6 +11,7 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	pb "github.com/cjdenio/uta-trax-api/proto"
 	"google.golang.org/protobuf/proto"
@@ -19,6 +21,8 @@ import (
 
 var scheduleDb *sql.DB
 
+var gtfsRtCache []byte
+
 func distance(lat1 float64, lng1 float64, lat2 float64, lng2 float64) float64 {
 	radlat1 := float64(math.Pi * lat1 / 180)
 	radlat2 := float64(math.Pi * lat2 / 180)
@@ -94,13 +98,21 @@ func fetchVehicleFeed() ([]byte, error) {
 }
 
 func getVehicles() ([]*pb.VehiclePosition, *pb.FeedHeader, error) {
-	bytes, err := fetchVehicleFeed()
-	if err != nil {
-		return nil, nil, err
+	var bytes []byte
+
+	if len(gtfsRtCache) > 0 {
+		bytes = gtfsRtCache
+	} else {
+		return nil, nil, errors.New("no cache")
+		var err error
+		bytes, err = fetchVehicleFeed()
+		if err != nil {
+			return nil, nil, err
+		}
 	}
 
 	feed := pb.FeedMessage{}
-	err = proto.Unmarshal(bytes, &feed)
+	err := proto.Unmarshal(bytes, &feed)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -211,6 +223,19 @@ func main() {
 
 	scheduleDb = _db
 
+	go func() {
+		for {
+			feed, err := fetchVehicleFeed()
+			if err == nil {
+				gtfsRtCache = feed
+				log.Println("refreshed cache")
+			} else {
+				log.Println(err)
+			}
+			time.Sleep(1 * time.Second)
+		}
+	}()
+
 	http.Handle("/", http.FileServer(http.Dir("./static")))
 
 	http.HandleFunc("/schema.proto", func(w http.ResponseWriter, r *http.Request) {