signal-upgrade close of closed channel (easegress-io#1190)

* use sync.once make sure channel is closed once when meet signal-upgrade

* update

pkg/api/dynamicmux.go

@@ -20,6 +20,7 @@ package api
 import (
  "net/http"
  "sort"
+ "sync"
  "sync/atomic"
 
  "github.com/go-chi/chi/v5"
@@ -32,8 +33,10 @@ import (
 type (
  dynamicMux struct {
  server *Server
- done chan struct{}
  router atomic.Value
+
+ done chan struct{}
+ closeOnce sync.Once
  }
 )
 
@@ -136,5 +139,12 @@ func (m *dynamicMux) reloadAPIs() {
 }
 
 func (m *dynamicMux) close() {
- close(m.done)
+ // make sure to close channel only once.
+ // when use "signal-upgrade", easegress will start a new process gracefully,
+ // which may cause the old process be closed twice.
+ // here we use sync.Once to make sure the channel is closed only once.
+ // more discussion here: https://github.com/easegress-io/easegress/issues/1170
+ m.closeOnce.Do(func() {
+ close(m.done)
+ })
 }