Update demo (#16)

* dockerfile cache dependencies

* reward service handle JSON errors correctly

* refactor bandit error handling, update rewards

examples/superstream_demo/Dockerfile

@@ -3,9 +3,10 @@ FROM golang:1.16 AS build
 ARG service_name
 
 WORKDIR /go/src/app
-COPY . .
-
+COPY go.* .
 RUN go mod download
+
+COPY . .
 RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -installsuffix cgo -o /app ./${service_name}
 
 FROM scratch

examples/superstream_demo/bandit/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"log"
 	"net/http"
@@ -15,58 +16,74 @@ import (
 	"github.com/stitchfix/mab/numint"
 )
 
-type randomizeRequest struct {
+func main() {
+	cli := &http.Client{Timeout: time.Second}
+	url := "http://reward-service/rewards"
+	parser := mab.ParseFunc(mab.BetaFromJSON)
+	marshaler := mab.MarshalFunc(json.Marshal)
+
+	bandit := mab.Bandit{
+		RewardSource: mab.NewHTTPSource(cli, url, parser, mab.WithContextMarshaler(marshaler)),
+		Strategy:     mab.NewThompson(numint.NewQuadrature()),
+		Sampler:      mab.NewSha1Sampler(),
+	}
+
+	r := mux.NewRouter()
+	r.HandleFunc("/select_arm", handler{bandit}.selectArm).Methods("POST")
+
+	server := &http.Server{
+		Handler: handlers.LoggingHandler(os.Stdout, r),
+		Addr:    "0.0.0.0:80",
+	}
+
+	log.Fatal(server.ListenAndServe())
+}
+
+type handler struct {
+	bandit mab.Bandit
+}
+
+type selectArmRequest struct {
 	Unit    string          `json:"unit"`
 	Context json.RawMessage `json:"context"`
 }
 
-var bandit mab.Bandit
+func (h handler) selectArm(w http.ResponseWriter, r *http.Request) {
+
+	defer r.Body.Close()
 
-func handler(w http.ResponseWriter, r *http.Request) {
-	var req randomizeRequest
+	var req selectArmRequest
 
-	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+	if err := h.decodeRequestBody(r.Body, &req); err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
 
-	result, err := bandit.SelectArm(r.Context(), req.Unit, req.Context)
+	result, err := h.bandit.SelectArm(r.Context(), req.Unit, req.Context)
+
 	if err != nil {
-		var non200 *mab.ErrRewardNon2XX
-		if errors.As(err, &non200) {
-			http.Error(w, err.Error(), err.(*mab.ErrRewardNon2XX).StatusCode)
-			return
-		}
-		http.Error(w, err.Error(), http.StatusInternalServerError)
+		h.writeError(w, err)
 		return
 	}
 
 	_ = json.NewEncoder(w).Encode(result)
 }
 
-func main() {
-	cli := &http.Client{Timeout: time.Second}
-	url := "http://reward-service/rewards"
-	parser := mab.ParseFunc(mab.BetaFromJSON)
-	marshaler := mab.MarshalFunc(json.Marshal)
-
-	bandit = mab.Bandit{
-		RewardSource: mab.NewHTTPSource(cli, url, parser, mab.WithContextMarshaler(marshaler)),
-		Strategy:     mab.NewThompson(numint.NewQuadrature()),
-		Sampler:      mab.NewSha1Sampler(),
+func (h handler) decodeRequestBody(b io.Reader, req *selectArmRequest) error {
+	if err := json.NewDecoder(b).Decode(req); err == io.EOF {
+		return fmt.Errorf("request body empty")
+	} else if err != nil {
+		return err
 	}
+	return nil
+}
 
-	r := mux.NewRouter()
-	r.HandleFunc("/randomize", handler).Methods("POST")
-	r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		io.WriteString(w, `{"alive": true}`)
-	})
-
-	server := &http.Server{
-		Handler: handlers.LoggingHandler(os.Stdout, r),
-		Addr:    "0.0.0.0:80",
+func (h handler) writeError(w http.ResponseWriter, err error) {
+	var non200 *mab.ErrRewardNon2XX
+	if errors.As(err, &non200) {
+		http.Error(w, err.Error(), err.(*mab.ErrRewardNon2XX).StatusCode)
+		return
 	}
-
-	log.Fatal(server.ListenAndServe())
+	http.Error(w, err.Error(), http.StatusInternalServerError)
+	return
 }

examples/superstream_demo/reward/main.go

@@ -20,28 +20,31 @@ func init() {
 
 	campaignRewards[1] = []struct{ Alpha, Beta float64 }{
 		{10, 125},
-		{4, 130},
-		{16, 80},
+		{34, 130},
+		{26, 95},
 		{25, 99},
 	}
 
 	campaignRewards[2] = []struct{ Alpha, Beta float64 }{
 		{25, 125},
-		{5, 50},
-		{7, 90},
-		{13, 200},
+		{10, 50},
+		{7, 35},
+		{57, 200},
 	}
 }
 
 // This function handles incoming post requests to the /rewards endpoint
 func handler(w http.ResponseWriter, r *http.Request) {
-	
+
 	// The request body must contain a JSON object with at least a "campaign_id" key and and integer value
 	var req struct {
 		CampaignID *int `json:"campaign_id"`
 	}
 
-	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+	if err := json.NewDecoder(r.Body).Decode(&req); err == io.EOF {
+		http.Error(w, "request body empty", http.StatusBadRequest)
+		return
+	} else if err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
@@ -54,7 +57,7 @@ func handler(w http.ResponseWriter, r *http.Request) {
 	// get the context-dependent reward estimates
 	rewards, ok := campaignRewards[*req.CampaignID]
 	if !ok {
-		http.Error(w, fmt.Sprintf("no rewards for campaign ID %d", req.CampaignID), http.StatusBadRequest)
+		http.Error(w, fmt.Sprintf("no rewards for campaign ID %d", *req.CampaignID), http.StatusBadRequest)
 		return
 	}