mirror of
https://github.com/crazybber/go-pattern-examples.git
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159 lines
3.7 KiB
Go
159 lines
3.7 KiB
Go
package messaging
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import (
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"context"
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"errors"
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"fmt"
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"time"
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)
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//Message for msg in Message bus
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type Message struct {
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Seq int
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Text string
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From Session //消息来源
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}
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//User for user
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type User struct {
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ID uint64
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Name string
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}
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//Session inherit user
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type Session struct {
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User
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Timestamp time.Time
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}
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//Subscription for user
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//Subscription is a session
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type Subscription struct {
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Session
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topicName string
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ctx context.Context
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cancel context.CancelFunc
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Ch chan<- Message //发送队列
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Inbox chan Message //接收消息的队列
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}
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func newSubscription(uid uint64, topicName string, UserQueueSize int) Subscription {
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ctx, cancel := context.WithCancel(context.Background())
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return Subscription{
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Session: Session{User{ID: uid}, time.Now()},
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ctx: ctx,
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cancel: cancel,
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Ch: make(chan<- Message, UserQueueSize), //用于跟单个用户通信的消息队列，用户发送消息
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Inbox: make(chan Message, UserQueueSize), //用于跟单个用户通信的消息队列,用户接收消息
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}
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}
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//Cancel Message
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func (s *Subscription) Cancel() {
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s.cancel()
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}
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//Publish 这个表示用户订阅到感兴趣的主题的时候，同时也可以发送消息，
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//Publish 但是，示例中不演示这个用途
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//Publish 只有当channel无数据，且channel被close了，才会返回ok=false
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//Publish a message to subscription queue
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func (s *Subscription) Publish(msg Message) error {
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select {
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case <-s.ctx.Done():
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return errors.New("Topic has been closed")
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default:
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s.Ch <- msg
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}
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return nil
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}
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//Receive message
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func (s *Subscription) Receive(out *Message) error {
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select {
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case <-s.ctx.Done():
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return errors.New("Topic has been closed")
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case <-time.After(time.Millisecond * 100):
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return errors.New("time out error")
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case *out = <-s.Inbox:
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return nil
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}
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}
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//Topic that user is interested in
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//Topic should locate in MQ
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type Topic struct {
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UserQueueSize int
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Name string
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Subscribers map[uint64]Subscription //user list
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MessageHistory []Message //当前主题的消息历史,实际项目中可能需要限定大小并设置过期时间
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}
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//Publish 只有当channel无数据，且channel被close了，才会返回ok=false
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//Publish a message to subscription queue
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func (t *Topic) Publish(msg Message) error {
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//将消息发布给当前Topic的所有人
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for usersID, subscription := range t.Subscribers {
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if subscription.ID == usersID {
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subscription.Inbox <- msg
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}
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}
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//save message history
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t.MessageHistory = append(t.MessageHistory, msg)
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fmt.Println("current histroy message count: ", len(t.MessageHistory))
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return nil
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}
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func (t *Topic) findUserSubscription(uid uint64, topicName string) (Subscription, bool) {
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// Get session or create one if it's the first
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if topicName != t.Name || t.Subscribers == nil || len(t.Subscribers) == 0 {
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return Subscription{}, false
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}
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if subscription, found := t.Subscribers[uid]; found {
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return subscription, true
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}
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return Subscription{}, false
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}
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//Subscribe a spec topic
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func (t *Topic) Subscribe(uid uint64, topicName string) (Subscription, bool) {
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if t.Name != topicName {
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return Subscription{}, false
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}
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// Get session or create one if it's the first
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if _, found := t.findUserSubscription(uid, topicName); !found {
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if t.Subscribers == nil {
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t.Subscribers = make(map[uint64]Subscription)
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}
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t.Subscribers[uid] = newSubscription(uid, topicName, t.UserQueueSize)
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}
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return t.Subscribers[uid], true
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}
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//Unsubscribe remove Subscription
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func (t *Topic) Unsubscribe(s Subscription) error {
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if _, found := t.findUserSubscription(s.ID, s.topicName); found {
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delete(t.Subscribers, s.ID)
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}
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return nil
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}
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//Delete topic
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func (t *Topic) Delete() error {
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t.Subscribers = nil
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t.Name = ""
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t.MessageHistory = nil
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return nil
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}
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