[#228] add support of multiple sockets

Signed-off-by: Pavel Pogodaev <p.pogodaev@yadro.com>

server.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+
+	"go.uber.org/zap"
+)
+
+type (
+	ServerInfo struct {
+		Address string
+		TLS     ServerTLSInfo
+	}
+
+	ServerTLSInfo struct {
+		Enabled  bool
+		CertFile string
+		KeyFile  string
+	}
+
+	Server interface {
+		Address() string
+		Listener() net.Listener
+		UpdateCert(certFile, keyFile string) error
+	}
+
+	server struct {
+		address     string
+		listener    net.Listener
+		tlsProvider *certProvider
+	}
+
+	certProvider struct {
+		Enabled bool
+
+		mu       sync.RWMutex
+		certPath string
+		keyPath  string
+		cert     *tls.Certificate
+	}
+)
+
+func (s *server) Address() string {
+	return s.address
+}
+
+func (s *server) Listener() net.Listener {
+	return s.listener
+}
+
+func (s *server) UpdateCert(certFile, keyFile string) error {
+	return s.tlsProvider.UpdateCert(certFile, keyFile)
+}
+
+func newServer(ctx context.Context, serverInfo ServerInfo, logger *zap.Logger) *server {
+	var lic net.ListenConfig
+	ln, err := lic.Listen(ctx, "tcp", serverInfo.Address)
+	if err != nil {
+		logger.Fatal("could not prepare listener", zap.String("address", serverInfo.Address), zap.Error(err))
+	}
+
+	tlsProvider := &certProvider{
+		Enabled: serverInfo.TLS.Enabled,
+	}
+
+	if serverInfo.TLS.Enabled {
+		if err = tlsProvider.UpdateCert(serverInfo.TLS.CertFile, serverInfo.TLS.KeyFile); err != nil {
+			logger.Fatal("failed to update cert", zap.Error(err))
+		}
+
+		ln = tls.NewListener(ln, &tls.Config{
+			GetCertificate: tlsProvider.GetCertificate,
+		})
+	}
+
+	return &server{
+		address:     serverInfo.Address,
+		listener:    ln,
+		tlsProvider: tlsProvider,
+	}
+}
+
+func (p *certProvider) GetCertificate(*tls.ClientHelloInfo) (*tls.Certificate, error) {
+	if !p.Enabled {
+		return nil, errors.New("cert provider: disabled")
+	}
+
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.cert, nil
+}
+
+func (p *certProvider) UpdateCert(certPath, keyPath string) error {
+	if !p.Enabled {
+		return fmt.Errorf("tls disabled")
+	}
+
+	cert, err := tls.LoadX509KeyPair(certPath, keyPath)
+	if err != nil {
+		return fmt.Errorf("cannot load TLS key pair from certFile '%s' and keyFile '%s': %w", certPath, keyPath, err)
+	}
+
+	p.mu.Lock()
+	p.certPath = certPath
+	p.keyPath = keyPath
+	p.cert = &cert
+	p.mu.Unlock()
+	return nil
+}
+
+func (p *certProvider) FilePaths() (string, string) {
+	if !p.Enabled {
+		return "", ""
+	}
+
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.certPath, p.keyPath
+}