Throttling middleware

.gitignore

@@ -0,0 +1,2 @@
+bin/
+simple-go-server

Makefile

@@ -0,0 +1,23 @@
+DOCKER_REGISTRY   ?= docker.io
+IMAGE_PREFIX      ?= enricofoltran
+SHORT_NAME        ?= simple-go-server
+
+# build options
+GO        ?= go
+TAGS      :=
+LDFLAGS   := -w -s
+GOFLAGS   :=
+BINDIR    := $(CURDIR)/bin
+
+.PHONY: all
+all: build
+
+.PHONY: build
+build:
+	GOBIN=$(BINDIR) $(GO) install $(GOFLAGS) -tags '$(TAGS)' -ldflags '$(LDFLAGS)'
+
+.PHONY: clean
+clean:
+	@rm -rf $(BINDIR)
+
+include versioning.mk

README.md

@@ -1,5 +1,5 @@
 # simple-go-server
-A simple golang web server with basic logging, tracing, health check, graceful shutdown and zero dependencies.
+A simple golang web server with basic logging, tracing, throttling, health check, graceful shutdown and zero dependencies.
 
 This repository originated from **[this](https://gist.github.com/enricofoltran/10b4a980cd07cb02836f70a4ab3e72d7)** Github gist, featured on [Hacker News](https://news.ycombinator.com/item?id=16090977).
 

main.go

@@ -18,17 +18,41 @@ const (
 	requestIDKey key = 0
 )
 
+// build info
+var (
+	Version      string = ""
+	GitTag       string = ""
+	GitCommit    string = ""
+	GitTreeState string = ""
+)
+
+// flags
 var (
 	listenAddr string
-	healthy    int32
+	rps        int
+	burst      int
+	timeout    time.Duration
 )
 
+var healthy int32
+
 func main() {
 	flag.StringVar(&listenAddr, "listen-addr", ":5000", "server listen address")
+	flag.IntVar(&rps, "rps", 425, "requests per second throttling limit")
+	flag.IntVar(&burst, "burst", 10, "concurrently handled requests before queueing")
+	flag.DurationVar(&timeout, "timeout", 75*time.Millisecond, "time after which quequed requests are dropped")
 	flag.Parse()
 
 	logger := log.New(os.Stdout, "http: ", log.LstdFlags)
+
+	logger.Println("Simple go server")
+	logger.Println("Version:", Version)
+	logger.Println("GitTag:", GitTag)
+	logger.Println("GitCommit:", GitCommit)
+	logger.Println("GitTreeState:", GitTreeState)
+
 	logger.Println("Server is starting...")
+	logger.Printf("Settings are: rps=%v burst=%v timeout=%v", rps, burst, timeout)
 
 	router := http.NewServeMux()
 	router.Handle("/", index())
@@ -39,8 +63,12 @@ func main() {
 	}
 
 	server := &http.Server{
-		Addr:         listenAddr,
-		Handler:      tracing(nextRequestID)(logging(logger)(router)),
+		Addr: listenAddr,
+		Handler: throttling(rps, burst, timeout)(
+			tracing(nextRequestID)(
+				logging(logger)(router),
+			),
+		),
 		ErrorLog:     logger,
 		ReadTimeout:  5 * time.Second,
 		WriteTimeout: 10 * time.Second,
@@ -82,6 +110,10 @@ func index() http.Handler {
 			http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
 			return
 		}
+		if r.Method != http.MethodGet {
+			http.Error(w, http.StatusText(http.StatusMethodNotAllowed), http.StatusMethodNotAllowed)
+			return
+		}
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 		w.Header().Set("X-Content-Type-Options", "nosniff")
 		w.WriteHeader(http.StatusOK)
@@ -127,3 +159,41 @@ func tracing(nextRequestID func() string) func(http.Handler) http.Handler {
 		})
 	}
 }
+
+// adapted from https://rodaine.com/2017/05/x-files-time-rate-golang/
+func throttling(rps, burst int, timeout time.Duration) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		limiter, _ := throttler(rps, burst)
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			timer := time.NewTimer(timeout)
+			select {
+			case <-limiter:
+				timer.Stop()
+			case <-timer.C:
+				http.Error(w, http.StatusText(http.StatusTooManyRequests), http.StatusTooManyRequests)
+				return
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
+func throttler(rps, burst int) (c chan time.Time, cancel func()) {
+	c = make(chan time.Time, burst)
+	for i := 0; i < burst; i++ {
+		c <- time.Now()
+	}
+
+	tick := time.NewTicker(time.Second / time.Duration(rps))
+	go func() {
+		for t := range tick.C {
+			select {
+			case c <- t:
+			default:
+			}
+		}
+		close(c)
+	}()
+
+	return c, tick.Stop
+}

rootfs/Dockerfile

@@ -0,0 +1,17 @@
+FROM alpine:3.8 as builder
+
+RUN apk update && apk add ca-certificates && rm -rf /var/cache/apk/*
+
+RUN adduser -D -g '' app
+
+# ---
+FROM scratch
+
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /etc/passwd /etc/passwd
+
+COPY simple-go-server /simple-go-server
+
+USER app
+
+ENTRYPOINT ["/simple-go-server"]

versioning.mk

@@ -0,0 +1,64 @@
+GIT_COMMIT = $(shell git rev-parse HEAD)
+GIT_SHA    = $(shell git rev-parse --short HEAD)
+GIT_TAG    = $(shell git describe --tags --abbrev=0 --exact-match 2>/dev/null)
+GIT_DIRTY  = $(shell test -n "`git status --porcelain`" && echo "dirty" || echo "clean")
+
+ifdef VERSION
+	DOCKER_VERSION = $(VERSION)
+	BINARY_VERSION = $(VERSION)
+endif
+
+MUTABLE_VERSION := canary
+DOCKER_VERSION  ?= git-${GIT_SHA}
+BINARY_VERSION  ?= ${GIT_TAG}
+
+# Only set Version if building a tag or VERSION is set
+ifneq ($(BINARY_VERSION),)
+	LDFLAGS += -X main.Version=${BINARY_VERSION}
+endif
+
+LDFLAGS += -X main.GitTag=${GIT_TAG}
+LDFLAGS += -X main.GitCommit=${GIT_SHA}
+LDFLAGS += -X main.GitTreeState=${GIT_DIRTY}
+
+IMAGE         := ${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${SHORT_NAME}:${DOCKER_VERSION}
+MUTABLE_IMAGE := ${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${SHORT_NAME}:${MUTABLE_VERSION}
+
+info:
+	@echo "Version:           ${VERSION}"
+	@echo "Git Tag:           ${GIT_TAG}"
+	@echo "Git Commit:        ${GIT_COMMIT}"
+	@echo "Git Tree State:    ${GIT_DIRTY}"
+	@echo "Docker Version:    ${DOCKER_VERSION}"
+	@echo "Registry:          ${DOCKER_REGISTRY}"
+	@echo "Immutable Image:   ${IMAGE}"
+	@echo "Mutable Image:     ${MUTABLE_IMAGE}"
+
+.PHONY: check-docker
+check-docker:
+	@if [ -z $$(which docker) ]; then \
+	  echo "Missing \`docker\` client which is required for development"; \
+	  exit 2; \
+	fi
+
+.PHONY: docker-binary
+docker-binary: BINDIR = $(CURDIR)/rootfs
+docker-binary: GOFLAGS += -a -installsuffix cgo
+docker-binary:
+	GOOS=linux GOARCH=amd64 CGO_ENABLED=0 $(GO) build -o $(BINDIR)/$(SHORT_NAME) $(GOFLAGS) -tags '$(TAGS)' -ldflags '$(LDFLAGS)'
+
+.PHONY: docker-build
+docker-build: check-docker docker-binary
+	docker build --rm -t ${IMAGE} rootfs
+	docker tag ${IMAGE} ${MUTABLE_IMAGE}
+
+.PHONY: docker-push
+docker-push: docker-mutable-push docker-immutable-push
+
+.PHONY: docker-immutable-push
+docker-immutable-push:
+	docker push ${IMAGE}
+
+.PHONY: docker-mutable-push
+docker-mutable-push:
+	docker push ${MUTABLE_IMAGE}