flathttp: impl http server that can have a config reloaded s.t. it ma…

…y listen to one or several net.Listeners or be shut down at any time

flathttp/config.go

@@ -0,0 +1,48 @@
+package flathttp
+
+import (
+	"fmt"
+	"net/url"
+	"time"
+)
+
+type Addr struct {
+	Addr   string
+	Scheme string
+	Host   string
+}
+
+type Config struct {
+	Addrs []string
+
+	MaxHeaderBytes    int
+	ReadTimeout       time.Duration
+	WriteTimeout      time.Duration
+	IdleTimeout       time.Duration
+	ReadHeaderTimeout time.Duration
+	ShutdownTimeout   time.Duration
+
+	addrs []Addr
+}
+
+func (c *Config) Parse() error {
+	for _, addr := range c.Addrs {
+		u, err := url.Parse(addr)
+		if err != nil {
+			return fmt.Errorf("flathttp: invalid addr provided in config %q", u)
+		}
+		switch u.Scheme {
+		case "tcp", "tcp4", "tcp6", "unix", "unixpacket":
+		case "http", "https":
+			u.Scheme = "tcp"
+		default:
+			return fmt.Errorf("flathttp: invalid scheme %q in addr %q (must be http, https, tcp, tcp4, tcp6, unix, unixpacket)", u.Scheme, addr)
+		}
+		c.addrs = append(c.addrs, Addr{Addr: addr, Scheme: u.Scheme, Host: u.Host})
+	}
+	return nil
+}
+
+func (c *Config) reset() {
+	c.addrs = c.addrs[:0]
+}

flathttp/server.go

@@ -0,0 +1,208 @@
+package flathttp
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+)
+
+var DefaultShutdownTimeout = 5 * time.Second
+
+var ErrAlreadyListening = errors.New("already listening")
+
+type Server struct {
+	cfg Config
+	srv *http.Server
+
+	lns  map[string]net.Listener // all listeners
+	wg   sync.WaitGroup          // all served goroutines
+	lm   sync.Mutex              // lifecycle mutex\
+	em   sync.Mutex              // errors mutex
+	errs []error                 // errors
+}
+
+func NewServer(cfg *Config) *Server {
+	if cfg == nil {
+		cfg = &Config{}
+	}
+	srv := &Server{
+		cfg: *cfg,
+		lns: make(map[string]net.Listener),
+	}
+	return srv
+}
+
+func (s *Server) Update(cfg *Config) {
+	s.lm.Lock()
+	defer s.lm.Unlock()
+
+	if cfg == nil {
+		cfg = &Config{}
+	}
+	s.cfg = *cfg
+}
+
+func (s *Server) Start() []error {
+	s.lm.Lock()
+	defer s.lm.Unlock()
+
+	err := s.start()
+	if err != nil {
+		return append([]error{err}, s.stop()...)
+	}
+	return nil
+}
+
+func (s *Server) start() error {
+	if err := s.cfg.Parse(); err != nil {
+		return err
+	}
+
+	s.srv = &http.Server{
+		MaxHeaderBytes:    s.cfg.MaxHeaderBytes,
+		ReadTimeout:       s.cfg.ReadTimeout,
+		WriteTimeout:      s.cfg.WriteTimeout,
+		IdleTimeout:       s.cfg.IdleTimeout,
+		ReadHeaderTimeout: s.cfg.ReadHeaderTimeout,
+	}
+
+	addrs := s.cfg.addrs
+	if len(addrs) == 0 {
+		addrs = append(addrs, Addr{Addr: "tcp://:0", Scheme: "tcp", Host: ":0"})
+	}
+
+	for _, a := range addrs {
+		err := s.listen(a)
+		if err == nil {
+			continue
+		}
+		if errors.Is(err, ErrAlreadyListening) {
+			continue
+		}
+		return err
+	}
+
+	return nil
+}
+
+func (s *Server) listen(a Addr) error {
+	srv := s.srv
+
+	_, exists := s.lns[a.Addr]
+	if exists {
+		return fmt.Errorf("flathttp [%s]: %w", a.Addr, ErrAlreadyListening)
+	}
+
+	ln, err := net.Listen(a.Scheme, a.Host)
+	if err != nil {
+		return fmt.Errorf("flathttp: failed to start listener for %q: %w", a, err)
+	}
+
+	fmt.Printf("Listening %q.\n", ln.Addr())
+
+	s.lns[a.Addr] = ln
+
+	// Start serving the listener.
+
+	s.wg.Add(1)
+	go func() {
+		defer s.wg.Done()
+
+		err := eof(srv.Serve(ln))
+		if err == nil {
+			return
+		}
+
+		err = fmt.Errorf("flathttp [%s] (serve error): %w", a.Addr, err)
+
+		s.em.Lock()
+		s.errs = append(s.errs, err)
+		s.em.Unlock()
+	}()
+
+	return nil
+}
+
+func (s *Server) Stop() []error {
+	s.lm.Lock()
+	defer s.lm.Unlock()
+
+	return s.stop()
+}
+
+func (s *Server) stop() []error {
+	var errs []error
+
+	// Gracefully shutdown the server.
+
+	timeout := s.cfg.ShutdownTimeout
+	if timeout <= 0 {
+		timeout = DefaultShutdownTimeout
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+
+	err := s.srv.Shutdown(ctx)
+	if err != nil {
+		errs = append(errs, fmt.Errorf("flathttp: failed to gracefully shutdown the server: %w", err))
+	}
+
+	<-ctx.Done()
+
+	errs = append(errs, s.close()...)
+
+	if cancel != nil {
+		cancel()
+	}
+
+	// Wait until all listeners are closed, and if errors rise up, include them in the result.
+
+	s.wg.Wait()
+
+	s.cfg.reset()
+
+	s.srv = nil
+
+	for addr := range s.lns {
+		delete(s.lns, addr)
+	}
+
+	errs = append(errs, s.errs...)
+	s.errs = s.errs[:0]
+
+	return errs
+}
+
+func eof(err error) error {
+	var op *net.OpError
+
+	switch {
+	case errors.As(err, &op) && op.Err.Error() == "use of closed network connection":
+		return nil
+	case errors.Is(err, http.ErrServerClosed):
+		return nil
+	case errors.Is(err, io.EOF):
+		return nil
+	default:
+		return err
+	}
+}
+
+func (s *Server) close() []error {
+	var errs []error
+
+	for addr, ln := range s.lns {
+		err := eof(ln.Close())
+		if err != nil {
+			err = fmt.Errorf("flathttp [%s] (listener close): %w", addr, err)
+			errs = append(errs, err)
+		}
+	}
+
+	return errs
+}

flathttp/server_test.go

@@ -0,0 +1,47 @@
+package flathttp
+
+import (
+	"github.com/stretchr/testify/require"
+	"go.uber.org/goleak"
+	"net"
+	"testing"
+	"time"
+)
+
+func getAvailableAddrs(t testing.TB, scheme string, n int) []string {
+	t.Helper()
+
+	addrs := make([]string, 0, n)
+	for i := 0; i < n; i++ {
+		ln, err := net.Listen(scheme, ":0")
+		require.NoError(t, err)
+		require.NoError(t, ln.Close())
+
+		addrs = append(addrs, scheme+"://"+ln.Addr().String())
+	}
+	return addrs
+}
+
+func TestServer(t *testing.T) {
+	defer goleak.VerifyNone(t)
+
+	srv := NewServer(
+		&Config{
+			Addrs:           getAvailableAddrs(t, "tcp", 1),
+			ShutdownTimeout: 100 * time.Millisecond,
+		},
+	)
+
+	for i := 0; i < 10; i++ {
+		require.Empty(t, srv.Start())
+
+		srv.Update(
+			&Config{
+				Addrs:           append(srv.cfg.Addrs, getAvailableAddrs(t, "tcp", 1)...),
+				ShutdownTimeout: 100 * time.Millisecond,
+			},
+		)
+	}
+
+	require.Empty(t, srv.Stop())
+}

go.mod

@@ -1,3 +1,11 @@
 module github.com/lithdew/flatend
 
 go 1.14
+
+require (
+	github.com/stretchr/testify v1.4.0
+	github.com/tidwall/gjson v1.6.0 // indirect
+	go.uber.org/goleak v1.0.0
+	golang.org/x/lint v0.0.0-20200302205851-738671d3881b // indirect
+	golang.org/x/tools v0.0.0-20200522201501-cb1345f3a375 // indirect
+)

go.sum

@@ -0,0 +1,50 @@
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+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
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