From e008ec29da3a2f2dde4076602dbed91deba76182 Mon Sep 17 00:00:00 2001
From: Jason <xjasonlyu@gmail.com>
Date: Wed, 14 Aug 2019 00:20:18 +0800
Subject: [PATCH] upgrade session with queue

---
 common/queue/queue.go           | 71 +++++++++++++++++++++++++++++++++
 common/stats/session/session.go | 31 +++++++-------
 2 files changed, 88 insertions(+), 14 deletions(-)
 create mode 100644 common/queue/queue.go

diff --git a/common/queue/queue.go b/common/queue/queue.go
new file mode 100644
index 0000000..777b63b
--- /dev/null
+++ b/common/queue/queue.go
@@ -0,0 +1,71 @@
+package queue
+
+import (
+	"sync"
+)
+
+// Queue is a simple concurrent safe queue
+type Queue struct {
+	items []interface{}
+	lock  sync.RWMutex
+}
+
+// Put add the item to the queue.
+func (q *Queue) Put(items ...interface{}) {
+	if len(items) == 0 {
+		return
+	}
+
+	q.lock.Lock()
+	q.items = append(q.items, items...)
+	q.lock.Unlock()
+}
+
+// Pop returns the head of items.
+func (q *Queue) Pop() interface{} {
+	if len(q.items) == 0 {
+		return nil
+	}
+
+	q.lock.Lock()
+	head := q.items[0]
+	q.items = q.items[1:]
+	q.lock.Unlock()
+	return head
+}
+
+// First returns the head of items without deleting.
+func (q *Queue) First() interface{} {
+	if len(q.items) == 0 {
+		return nil
+	}
+
+	q.lock.RLock()
+	head := q.items[0]
+	q.lock.RUnlock()
+	return head
+}
+
+// Copy get the copy of queue.
+func (q *Queue) Copy() []interface{} {
+	items := make([]interface{}, 0)
+	q.lock.RLock()
+	items = append(items, q.items...)
+	q.lock.RUnlock()
+	return items
+}
+
+// Len returns the number of items in this queue.
+func (q *Queue) Len() int64 {
+	q.lock.Lock()
+	defer q.lock.Unlock()
+
+	return int64(len(q.items))
+}
+
+// New is a constructor for a new concurrent safe queue.
+func New(hint int64) *Queue {
+	return &Queue{
+		items: make([]interface{}, 0, hint),
+	}
+}
diff --git a/common/stats/session/session.go b/common/stats/session/session.go
index 1f0357d..3df7ae7 100644
--- a/common/stats/session/session.go
+++ b/common/stats/session/session.go
@@ -10,6 +10,7 @@ import (
 	"sync/atomic"
 
 	"github.com/xjasonlyu/tun2socks/common/log"
+	"github.com/xjasonlyu/tun2socks/common/queue"
 	"github.com/xjasonlyu/tun2socks/common/stats"
 )
 
@@ -23,11 +24,9 @@ var (
 )
 
 type simpleSessionStater struct {
-	sync.Mutex
-
-	server            *http.Server
-	activeSessionMap  sync.Map
-	completedSessions []*stats.Session
+	server                *http.Server
+	activeSessionMap      sync.Map
+	completedSessionQueue *queue.Queue
 }
 
 func NewSimpleSessionStater() stats.SessionStater {
@@ -40,11 +39,17 @@ func (s *simpleSessionStater) Start() {
 		// Make a snapshot.
 		var activeSessions []*stats.Session
 		s.activeSessionMap.Range(func(key, value interface{}) bool {
-			sess := value.(*stats.Session)
-			activeSessions = append(activeSessions, sess)
+			activeSessions = append(activeSessions, value.(*stats.Session))
 			return true
 		})
 
+		var completedSessions []*stats.Session
+		for _, item := range s.completedSessionQueue.Copy() {
+			if sess, ok := item.(*stats.Session); ok {
+				completedSessions = append(completedSessions, sess)
+			}
+		}
+
 		tablePrint := func(w io.Writer, sessions []*stats.Session) {
 			// Sort by session start time.
 			sort.Slice(sessions, func(i, j int) bool {
@@ -85,8 +90,8 @@ func (s *simpleSessionStater) Start() {
 		_, _ = fmt.Fprintf(w, "<p>Active sessions %d</p>", len(activeSessions))
 		tablePrint(w, activeSessions)
 		_, _ = fmt.Fprintf(w, "<br/><br/>")
-		_, _ = fmt.Fprintf(w, "<p>Recently completed sessions %d</p>", len(s.completedSessions))
-		tablePrint(w, s.completedSessions)
+		_, _ = fmt.Fprintf(w, "<p>Recently completed sessions %d</p>", len(completedSessions))
+		tablePrint(w, completedSessions)
 		_, _ = fmt.Fprintf(w, "</html>")
 		_ = w.Flush()
 	}
@@ -118,12 +123,10 @@ func (s *simpleSessionStater) GetSession(key interface{}) *stats.Session {
 func (s *simpleSessionStater) RemoveSession(key interface{}) {
 	if sess, ok := s.activeSessionMap.Load(key); ok {
 		// move to completed sessions
-		s.Lock()
-		s.completedSessions = append(s.completedSessions, sess.(*stats.Session))
-		if len(s.completedSessions) > maxCompletedSessions {
-			s.completedSessions = s.completedSessions[1:]
+		s.completedSessionQueue.Put(sess)
+		if s.completedSessionQueue.Len() > maxCompletedSessions {
+			s.completedSessionQueue.Pop()
 		}
-		s.Unlock()
 		// delete
 		s.activeSessionMap.Delete(key)
 	}