fix(proxy): fail fast on HTTP bind errors

Co-Authored-By: Virgil <virgil@lethean.io>

http_auth_test.go

@@ -1,7 +1,9 @@
 package proxy
 
 import (
+	"net"
 	"net/http"
+	"strconv"
 	"testing"
 )
 
@@ -69,3 +71,53 @@ func TestProxy_allowHTTP_Ugly(t *testing.T) {
 		t.Fatalf("expected status %d, got %d", http.StatusUnauthorized, status)
 	}
 }
+
+func TestProxy_startHTTP_Good(t *testing.T) {
+	p := &Proxy{
+		config: &Config{
+			HTTP: HTTPConfig{
+				Enabled: true,
+				Host:    "127.0.0.1",
+				Port:    0,
+			},
+		},
+		done: make(chan struct{}),
+	}
+
+	if ok := p.startHTTP(); !ok {
+		t.Fatal("expected HTTP server to start on a free port")
+	}
+	p.Stop()
+}
+
+func TestProxy_startHTTP_Bad(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen on ephemeral port: %v", err)
+	}
+	defer listener.Close()
+
+	host, port, err := net.SplitHostPort(listener.Addr().String())
+	if err != nil {
+		t.Fatalf("split listener addr: %v", err)
+	}
+	portNum, err := strconv.Atoi(port)
+	if err != nil {
+		t.Fatalf("parse listener port: %v", err)
+	}
+
+	p := &Proxy{
+		config: &Config{
+			HTTP: HTTPConfig{
+				Enabled: true,
+				Host:    host,
+				Port:    uint16(portNum),
+			},
+		},
+		done: make(chan struct{}),
+	}
+
+	if ok := p.startHTTP(); ok {
+		t.Fatal("expected HTTP server start to fail when the port is already in use")
+	}
+}

state_impl.go

@@ -220,7 +220,10 @@ func (p *Proxy) Start() {
 		p.watcher.Start()
 	}
 	if p.config.HTTP.Enabled {
-		p.startHTTP()
+		if !p.startHTTP() {
+			p.Stop()
+			return
+		}
 	}
 	p.ticker = time.NewTicker(time.Second)
 	go func() {
@@ -585,7 +588,10 @@ func parseTLSVersion(value string) uint16 {
 	}
 }
 
-func (p *Proxy) startHTTP() {
+func (p *Proxy) startHTTP() bool {
+	if p == nil || !p.config.HTTP.Enabled {
+		return true
+	}
 	mux := http.NewServeMux()
 	mux.HandleFunc("/1/summary", func(w http.ResponseWriter, r *http.Request) {
 		if status, ok := p.allowHTTP(r); !ok {
@@ -618,10 +624,18 @@ func (p *Proxy) startHTTP() {
 		p.writeJSON(w, p.minersDocument())
 	})
 	addr := net.JoinHostPort(p.config.HTTP.Host, strconv.Itoa(int(p.config.HTTP.Port)))
+	listener, err := net.Listen("tcp", addr)
+	if err != nil {
+		return false
+	}
 	p.httpServer = &http.Server{Addr: addr, Handler: mux}
 	go func() {
-		_ = p.httpServer.ListenAndServe()
+		err := p.httpServer.Serve(listener)
+		if err != nil && !errors.Is(err, http.ErrServerClosed) {
+			p.Stop()
+		}
 	}()
+	return true
 }
 
 func (p *Proxy) allowHTTP(r *http.Request) (int, bool) {