共计 4000 个字符,预计需要花费 10 分钟才能阅读完成。
上一篇文章咱们定义了音讯体和根底工具,这一篇咱们开始着手客户端的处理函数和 channel 的根底设计。
客户端处理函数
这里所谓的客户端指的是消费者,处理函数也就是解决消费者同咱们服务之间的 tcp 连贯。咱们定义一个构造体 Client,外面蕴含有连贯和状态字段,而后就是编写读写状态和 tcp 连贯的相干函数。
client.go
package server
import (
"encoding/binary"
"io"
"log"
)
type Client struct {
conn io.ReadWriteCloser
name string
state int
}
func NewClient(conn io.ReadWriteCloser, name string) *Client {return &Client{conn, name, -1}
}
func (c *Client) String() string {return c.name}
func (c *Client) GetState() int {return c.state}
func (c *Client) SetState(state int) {c.state = state}
func (c *Client) Read(data []byte) (int, error) {return c.conn.Read(data)
}
func (c *Client) Write(data []byte) (int, error) {
var err error
err = binary.Write(c.conn, binary.BigEndian, int32(len(data)))
if err != nil {return 0, err}
n, err := c.conn.Write(data)
if err != nil {return 0, err}
return n + 4, nil
}
func (c *Client) Close() {log.Printf("CLIENT(%s): closing", c.String())
c.conn.Close()}
这里的逻辑比较简单,惟一值得一提的是 Write 办法。在给消费者写音讯之前,咱们先往连贯中写入音讯体的长度,固定为 4 个字节,这样客户端读取的时候就能够先读取长度,而后按长度读取音讯。
channel
从上篇文章中咱们能够晓得,channel 是咱们这个音讯队列中的外围数据结构之一,因而它的设计尤为重要。
保护消费者信息
首先,因为咱们的消费者是从 channel 中读取音讯的,所以 channel 中须要保护消费者的信息,并且能够增删消费者。因而咱们先在 channel 构造中保护一个 consumer 数组和两个管道用来接管增删 consumer 的音讯:
type Consumer interface {Close()
}
type Channel struct {
name string
addClientChan chan util.ChanReq
removeClientChan chan util.ChanReq
clients []Consumer}
func (c *Channel) AddClient(client Consumer) {log.Printf("Channel(%s): adding client...", c.name)
doneChan := make(chan interface{})
c.addClientChan <- util.ChanReq{
Variable: client,
RetChan: doneChan,
}
<-doneChan
}
func (c *Channel) RemoveClient(client Consumer) {log.Printf("Channel(%s): removing client...", c.name)
doneChan := make(chan interface{})
c.removeClientChan <- util.ChanReq{
Variable: client,
RetChan: doneChan,
}
<-doneChan
}
值得注意的是,这里咱们没有间接绑定下面的 Client 构造体,而是形象出了一个 Consumer 接口。这样做的益处是倒转依赖关系,而且能够防止包循环援用。
既然有了接管音讯的管道,那么咱们须要一个常驻后盾的 goroutine 来解决这些音讯,能够称之为事件处理循环,也就是一个 for + select 组合:
// Router handles the events of Channel
func (c *Channel) Router() {
var clientReq util.ChanReq
for {
select {
case clientReq = <-c.addClientChan:
client := clientReq.Variable.(Consumer)
c.clients = append(c.clients, client)
log.Printf("CHANNEL(%s) added client %#v", c.name, client)
clientReq.RetChan <- struct{}{}
case clientReq = <-c.removeClientChan:
client := clientReq.Variable.(Consumer)
indexToRemove := -1
for k, v := range c.clients {
if v == client {
indexToRemove = k
break
}
}
if indexToRemove == -1 {log.Printf("ERROR: could not find client(%#v) in clients(%#v)", client, c.clients)
} else {c.clients = append(c.clients[:indexToRemove], c.clients[indexToRemove+1:]...)
log.Printf("CHANNEL(%s) removed client %#v", c.name, client)
}
clientReq.RetChan <- struct{}{}
}
}
}
收发音讯
对于收发音讯,这里咱们应用三个管道来实现:
- msgChan:这是一个有缓冲管道,用来暂存音讯,超过长度则抛弃音讯(后续会加上长久化到磁盘的性能)
- incomingMessageChan:用来接管生产者的音讯
- clientMessageChan:音讯会被发送到这个管道,后续会由消费者拉取
代码如下:
type Channel struct {
...
incomingMessageChan chan *Message
msgChan chan *Message
clientMessageChan chan *Message
}
func (c *Channel) PutMessage(msg *Message) {c.incomingMessageChan <- msg}
func (c *Channel) PullMessage() *Message {return <-c.clientMessageChan}
func (c *Channel) Router() {
var clientReq util.ChanReq
go c.MessagePump()
for {
select {
...
case msg := <-c.incomingMessageChan:
// 避免因 msgChan 缓冲填满时造成阻塞,加上一个 default 分支间接抛弃音讯
select {
case c.msgChan <- msg:
log.Printf("CHANNEL(%s) wrote message", c.name)
default:
}
}
}
}
// MessagePump send messages to ClientMessageChan
func (c *Channel) MessagePump() {
var msg *Message
for {
select {case msg = <-c.msgChan:}
c.clientMessageChan <- msg
}
}
敞开
当 channel 敞开的时候,咱们须要做一些清理的工作,首先咱们减少一个接管敞开信号的管道,在接管到信号时敞开发送音讯的 MessagePump 协程和消费者连贯,代码如下:
type Channel struct {
...
exitChan chan util.ChanReq
}
func (c *Channel) Router() {
var (
...
closeChan = make(chan struct{})
)
go c.MessagePump(closeChan)
for {
select {
...
case closeReq := <-c.exitChan:
log.Printf("CHANNEL(%s) is closing", c.name)
close(closeChan)
for _, consumer := range c.clients {consumer.Close()
}
closeReq.RetChan <- nil
}
}
}
// MessagePump send messages to ClientMessageChan
func (c *Channel) MessagePump(closeChan chan struct{}) {
var msg *Message
for {
select {
...
case <-closeChan:
return
}
...
}
}
func (c *Channel) Close() error {errChan := make(chan interface{})
c.exitChan <- util.ChanReq{RetChan: errChan,}
err, _ := (<-errChan).(error)
return err
}
咱们在事件处理循环中初始化一个管道,并作为参数传递给 MessagePump 协程,当接管到敞开信号时敞开此管道,而后顺次敞开消费者连贯,敞开逻辑就完结了。
channel 的残缺代码如下:
channel.go
此时咱们的目录构造为: