Add new --max-conn config

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master
 
+- Added `--max-conn` option to limit simultaneous server connections. ([@skryukov][])
+
 - Added `data_sent_bytes_total` and `data_rcvd_bytes_total` metrics. ([@palkan][])
 
 - Add `--allowed_origins` option to enable Origin check during the WebSocket upgrade. ([@skryukov][])

cli/cli.go

@@ -57,6 +57,7 @@ func NewRunner(name string, config *config.Config) *Runner {
 	// Set global HTTP params as early as possible to make sure all servers use them
 	server.SSL = &config.SSL
 	server.Host = config.Host
+	server.MaxConn = config.MaxConn
 
 	return &Runner{name: name, config: config, shutdownables: []Shutdownable{}, errChan: make(chan error)}
 }

cli/options.go

@@ -46,6 +46,7 @@ func init() {
 	// Config vars
 	fs.StringVar(&defaults.Host, "host", "localhost", "")
 	fs.IntVar(&defaults.Port, "port", portDefault, "")
+	fs.IntVar(&defaults.MaxConn, "max-conn", 0, "")
 	fs.StringVar(&defaults.Path, "path", "/cable", "")
 	fs.StringVar(&defaults.HealthPath, "health-path", "/health", "")
 
@@ -133,6 +134,7 @@ USAGE
 OPTIONS
   --host                                 Server host, default: localhost, env: ANYCABLE_HOST
   --port                                 Server port, default: 8080, env: ANYCABLE_PORT, PORT
+  --max-conn                             Limit simultaneous server connections (0 – without limit), default: 0, env: ANYCABLE_MAX_CONN
   --path                                 WebSocket endpoint path, default: /cable, env: ANYCABLE_PATH
   --health-path                          HTTP health endpoint path, default: /health, env: ANYCABLE_HEALTH_PATH
 

config/config.go

@@ -17,6 +17,7 @@ type Config struct {
 	HTTPPubSub           pubsub.HTTPConfig
 	Host                 string
 	Port                 int
+	MaxConn              int
 	BroadcastAdapter     string
 	Path                 string
 	HealthPath           string

go.mod

@@ -19,7 +19,7 @@ require (
 	github.com/pkg/errors v0.8.1 // indirect
 	github.com/stretchr/testify v1.7.0
 	github.com/syossan27/tebata v0.0.0-20180602121909-b283fe4bc5ba
-	golang.org/x/net v0.0.0-20200506145744-7e3656a0809f // indirect
+	golang.org/x/net v0.0.0-20200506145744-7e3656a0809f
 	golang.org/x/sys v0.0.0-20210420205809-ac73e9fd8988 // indirect
 	google.golang.org/genproto v0.0.0-20200511104702-f5ebc3bea380 // indirect
 	google.golang.org/grpc v1.29.1

metrics/metrics.go

@@ -59,7 +59,7 @@ func FromConfig(config *Config) (*Metrics, error) {
 
 	if config.HTTPEnabled() {
 		if config.Host != "" && config.Host != server.Host {
-			srv, err := server.NewServer(config.Host, strconv.Itoa(config.Port), server.SSL)
+			srv, err := server.NewServer(config.Host, strconv.Itoa(config.Port), server.SSL, 0)
 			if err != nil {
 				return nil, err
 			}

server/server.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 
 	"github.com/apex/log"
+	"golang.org/x/net/netutil"
 )
 
 // HTTPServer is wrapper over http.Server
@@ -19,6 +20,7 @@ type HTTPServer struct {
 	secured  bool
 	shutdown bool
 	started  bool
+	maxConn  int
 	mu       sync.Mutex
 	log      *log.Entry
 
@@ -31,12 +33,14 @@ var (
 	Host string = "localhost"
 	// SSL is a default configuration for HTTP servers
 	SSL *SSLConfig
+	// MaxConn is a default configuration for maximum connections
+	MaxConn int
 )
 
 // ForPort creates new or returns the existing server for the specified port
 func ForPort(port string) (*HTTPServer, error) {
 	if _, ok := allServers[port]; !ok {
-		server, err := NewServer(Host, port, SSL)
+		server, err := NewServer(Host, port, SSL, MaxConn)
 		if err != nil {
 			return nil, err
 		}
@@ -47,7 +51,7 @@ func ForPort(port string) (*HTTPServer, error) {
 }
 
 // NewServer builds HTTPServer from config params
-func NewServer(host string, port string, ssl *SSLConfig) (*HTTPServer, error) {
+func NewServer(host string, port string, ssl *SSLConfig, maxConn int) (*HTTPServer, error) {
 	mux := http.NewServeMux()
 	addr := net.JoinHostPort(host, port)
 
@@ -72,6 +76,7 @@ func NewServer(host string, port string, ssl *SSLConfig) (*HTTPServer, error) {
 		secured:  secured,
 		shutdown: false,
 		started:  false,
+		maxConn:  maxConn,
 		log:      log.WithField("context", "http"),
 	}, nil
 }
@@ -87,11 +92,21 @@ func (s *HTTPServer) Start() error {
 	s.started = true
 	s.mu.Unlock()
 
+	ln, err := net.Listen("tcp", s.addr)
+	if err != nil {
+		return err
+	}
+	defer ln.Close()
+
+	if s.maxConn > 0 {
+		ln = netutil.LimitListener(ln, s.maxConn)
+	}
+
 	if s.secured {
-		return s.server.ListenAndServeTLS("", "")
+		return s.server.ServeTLS(ln, "", "")
 	}
 
-	return s.server.ListenAndServe()
+	return s.server.Serve(ln)
 }
 
 // StartAndAnnounce prints server info and starts server

vendor/modules.txt

@@ -65,6 +65,7 @@ golang.org/x/net/http2
 golang.org/x/net/http2/hpack
 golang.org/x/net/idna
 golang.org/x/net/internal/timeseries
+golang.org/x/net/netutil
 golang.org/x/net/trace
 # golang.org/x/sys v0.0.0-20210420205809-ac73e9fd8988
 ## explicit