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|
// Package gracehttp provides easy to use graceful restart
// functionality for HTTP server.
package gracehttp
import (
"bytes"
"crypto/tls"
"fmt"
"log"
"net"
"net/http"
"os"
"os/signal"
"sync"
"syscall"
"github.com/facebookgo/grace/gracenet"
"github.com/facebookgo/httpdown"
)
var (
logger *log.Logger
didInherit = os.Getenv("LISTEN_FDS") != ""
ppid = os.Getppid()
)
// An app contains one or more servers and associated configuration.
type app struct {
servers []*http.Server
http *httpdown.HTTP
net *gracenet.Net
listeners []net.Listener
sds []httpdown.Server
errors chan error
}
func newApp(servers []*http.Server) *app {
return &app{
servers: servers,
http: &httpdown.HTTP{},
net: &gracenet.Net{},
listeners: make([]net.Listener, 0, len(servers)),
sds: make([]httpdown.Server, 0, len(servers)),
// 2x num servers for possible Close or Stop errors + 1 for possible
// StartProcess error.
errors: make(chan error, 1+(len(servers)*2)),
}
}
func (a *app) listen() error {
for _, s := range a.servers {
// TODO: default addresses
l, err := a.net.Listen("tcp", s.Addr)
if err != nil {
return err
}
if s.TLSConfig != nil {
l = tls.NewListener(l, s.TLSConfig)
}
a.listeners = append(a.listeners, l)
}
return nil
}
func (a *app) serve() {
for i, s := range a.servers {
a.sds = append(a.sds, a.http.Serve(s, a.listeners[i]))
}
}
func (a *app) wait() {
var wg sync.WaitGroup
wg.Add(len(a.sds) * 2) // Wait & Stop
go a.signalHandler(&wg)
for _, s := range a.sds {
go func(s httpdown.Server) {
defer wg.Done()
if err := s.Wait(); err != nil {
a.errors <- err
}
}(s)
}
wg.Wait()
}
func (a *app) term(wg *sync.WaitGroup) {
for _, s := range a.sds {
go func(s httpdown.Server) {
defer wg.Done()
if err := s.Stop(); err != nil {
a.errors <- err
}
}(s)
}
}
func (a *app) signalHandler(wg *sync.WaitGroup) {
ch := make(chan os.Signal, 10)
signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM, syscall.SIGUSR2)
for {
sig := <-ch
switch sig {
case syscall.SIGINT, syscall.SIGTERM:
// this ensures a subsequent INT/TERM will trigger standard go behaviour of
// terminating.
signal.Stop(ch)
a.term(wg)
return
case syscall.SIGUSR2:
// we only return here if there's an error, otherwise the new process
// will send us a TERM when it's ready to trigger the actual shutdown.
if _, err := a.net.StartProcess(); err != nil {
a.errors <- err
}
}
}
}
// Serve will serve the given http.Servers and will monitor for signals
// allowing for graceful termination (SIGTERM) or restart (SIGUSR2).
func Serve(servers ...*http.Server) error {
a := newApp(servers)
// Acquire Listeners
if err := a.listen(); err != nil {
return err
}
// Some useful logging.
if logger != nil {
if didInherit {
if ppid == 1 {
logger.Printf("Listening on init activated %s", pprintAddr(a.listeners))
} else {
const msg = "Graceful handoff of %s with new pid %d and old pid %d"
logger.Printf(msg, pprintAddr(a.listeners), os.Getpid(), ppid)
}
} else {
const msg = "Serving %s with pid %d"
logger.Printf(msg, pprintAddr(a.listeners), os.Getpid())
}
}
// Start serving.
a.serve()
// Close the parent if we inherited and it wasn't init that started us.
if didInherit && ppid != 1 {
if err := syscall.Kill(ppid, syscall.SIGTERM); err != nil {
return fmt.Errorf("failed to close parent: %s", err)
}
}
waitdone := make(chan struct{})
go func() {
defer close(waitdone)
a.wait()
}()
select {
case err := <-a.errors:
if err == nil {
panic("unexpected nil error")
}
return err
case <-waitdone:
if logger != nil {
logger.Printf("Exiting pid %d.", os.Getpid())
}
return nil
}
}
// Used for pretty printing addresses.
func pprintAddr(listeners []net.Listener) []byte {
var out bytes.Buffer
for i, l := range listeners {
if i != 0 {
fmt.Fprint(&out, ", ")
}
fmt.Fprint(&out, l.Addr())
}
return out.Bytes()
}
// SetLogger sets logger to be able to grab some useful logs
func SetLogger(l *log.Logger) {
logger = l
}
|
