前言
本篇博文是《从 0 到 1 学习 Netty》中 NIO 系列的第五篇博文,次要内容是 应用多线程对程序进行优化,充分利用 CPU 的能力,往期系列文章请拜访博主的 Netty 专栏,博文中的所有代码全副收集在博主的 GitHub 仓库中;
引入
这前几篇文章中,都是采纳单线程进行设计,尽管能够运行,然而没有充分利用 CPU 的性能,并且如果有一个事件的解决工夫较长,则会影响其余事件的解决。
例如,开发一个我的项目,如果团队只有一个全栈工程师,那么他须要先实现前端,再实现后端,只能循序渐进的实现工作,如果前端开发遭逢艰难,破费了很多工夫,则会大大拉长我的项目开发周期,而如果一个团队里有前端工程师和后端工程师,则前后端的开发能同步进行,这样会大大提高开发效率。
同理,对之前的代码进行优化,分两组选择器:
- 抉择一个线程配置一个选择器,作为‘Boss’,专门解决
accept
事件; - 创立多个线程(最好与 CPU 外围数始终),作为‘Worker’,每个线程配置一个选择器,轮流解决
read
,write
等事件
实现
1、创立一个 Boss 线程,负责解决 accept
事件类型:
Thread.currentThread().setName("Boss");
Selector boss = Selector.open();
ServerSocketChannel ssc = ServerSocketChannel.open();
ssc.configureBlocking(false);
SelectionKey bossKey = ssc.register(boss, 0, null);
bossKey.interestOps(SelectionKey.OP_ACCEPT);
ssc.bind(new InetSocketAddress(7999));
while (true) {boss.select();
Iterator<SelectionKey> iter = boss.selectedKeys().iterator();
while (iter.hasNext()) {SelectionKey key = iter.next();
iter.remove();
if (key.isAcceptable()) {ServerSocketChannel channel = (ServerSocketChannel) key.channel();
SocketChannel sc = channel.accept();
sc.configureBlocking(false);
}
}
}
2、创立 Worker
类,用于初始化 Worker 线程和 Selector,负责解决 read
事件类型:
class Worker implements Runnable{
private Thread thread;
private volatile Selector worker;
private String name;
public Worker(String name) {this.name = name;}
public void register() throws IOException {this.thread = new Thread(this, this.name);
this.worker = Selector.open();
this.thread.start();}
@Override
public void run() {while (true) {
try {this.worker.select();
Iterator<SelectionKey> iter = this.worker.selectedKeys().iterator();
while (iter.hasNext()) {SelectionKey key = iter.next();
iter.remove();
if (key.isReadable()) {ByteBuffer buffer = ByteBuffer.allocate(16);
SocketChannel channel = (SocketChannel) key.channel();
channel.read(buffer);
buffer.flip();
debugAll(buffer);
}
}
} catch (IOException e) {throw new RuntimeException(e);
}
}
}
}
然而这里会有个问题,每次进行 register()
的时候会新创建一个线程,但咱们只想一个 Worker 对应一个线程,所以咱们须要对上述代码进行优化,应用标志符来进行判断是否实现过初始化:
private volatile boolean start = false;
public void register() throws IOException {if (!this.start) {this.thread = new Thread(this, this.name);
this.selector = Selector.open();
this.thread.start();
this.start = true;
}
}
留神,this.worker = Selector.open();
与 this.thread.start();
不要写反了,不然之后运行会呈现空指针异样:
Exception in thread "worker-0" java.lang.NullPointerException
at com.sidiot.netty.c3.MultiThreadServer$Worker.run(MultiThreadServer.java:75)
at java.base/java.lang.Thread.run(Thread.java:832)
3、将 Worker 进行关联,先创立一个 worker 线程:
Worker worker0 = new Worker("worker-0");
worker0.register();
while (true) {
...
while (iter.hasNext()) {
...
if (key.isAcceptable()) {
...
log.debug("connected... {}", sc.getRemoteAddress());
log.debug("before register {}", sc.getRemoteAddress());
sc.register(worker0.selector, SelectionKey.OP_READ, null);
log.debug("after register {}", sc.getRemoteAddress());
}
}
}
4、编写客户端:
public class MultiThreadClient {public static void main(String[] args) throws IOException {SocketChannel sc = SocketChannel.open();
sc.connect(new InetSocketAddress("localhost", 7999));
sc.write(Charset.defaultCharset().encode("Hello, World! --sidiot."));
System.in.read();}
}
5、运行服务端和客户端,运行后果如下:
20:30:30 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - connected... /127.0.0.1:50612
20:30:30 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - before register /127.0.0.1:50612
20:30:30 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - after register /127.0.0.1:50612
发现 worker 并没有进行工作,或者说是客户端发送的数据并没有进入到 worker 的 可读事件 中,这是因为在 worker 的 run()
办法运行时,SocketChannel
还没有注册到 worker 的 selector 中,导致 worker 线程在 this.selector.select();
的地位产生了阻塞;
6、因为 sc.register
产生在 boss 线程中,而 select
产生在 worker 线程中,无奈确定两个线程的执行程序,因而须要把两步操作都放入一个线程中;
将 SocketChannel
传到到 Worker 的 register()
办法中:
public void register(SocketChannel sc) throws IOException {if (!this.start) {this.thread = new Thread(this, this.name);
this.selector = Selector.open();
this.thread.start();
this.start = true;
}
sc.register(this.selector, SelectionKey.OP_READ, null);
}
但这样还是不行的,因为 register()
办法还是在 boss 线程中执行,这就须要应用队列来实现线程间的通信了:
private ConcurrentLinkedQueue<Runnable> queue = new ConcurrentLinkedQueue<>();
public void register(SocketChannel sc) throws IOException {
...
this.queue.add(() -> {
try {sc.register(this.selector, SelectionKey.OP_READ, null);
} catch (ClosedChannelException e) {throw new RuntimeException(e);
}
});
this.selector.wakeup();}
@Override
public void run() {while (true) {
try {this.selector.select();
Runnable task = this.queue.poll();
if (task != null) {task.run();
}
Iterator<SelectionKey> iter = this.selector.selectedKeys().iterator();
...
}
}
留神,这里须要 this.selector.wakeup();
来唤醒 selector 持续往下走;
还有另一种办法,参考代码点击这里;
7、将单线程 worker 转成多线程:
Worker[] workers = new Worker[4];
for (int i = 0; i < workers.length; i++) {workers[i] = new Worker("worker-" + i);
}
同时应用计数器来实现各个 worker 线程的轮询应用:
AtomicInteger index = new AtomicInteger();
while (true) {
...
while (iter.hasNext()) {
...
if (key.isAcceptable()) {
...
workers[index.getAndIncrement() % workers.length].register(sc);
}
}
}
运行后果:
22:36:13 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - connected... /127.0.0.1:54668
22:36:13 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - before register /127.0.0.1:54668
22:36:13 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - after register /127.0.0.1:54668
22:36:13 [DEBUG] [worker-0] c.s.n.c.MultiThreadServer - read... /127.0.0.1:54668
+--------+-------------------- all ------------------------+----------------+
position: [0], limit: [7]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 73 69 64 69 6f 74 2e 00 00 00 00 00 00 00 00 00 |sidiot..........|
+--------+-------------------------------------------------+----------------+
22:36:20 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - connected... /127.0.0.1:54676
22:36:20 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - before register /127.0.0.1:54676
22:36:20 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - after register /127.0.0.1:54676
22:36:20 [DEBUG] [worker-1] c.s.n.c.MultiThreadServer - read... /127.0.0.1:54676
+--------+-------------------- all ------------------------+----------------+
position: [0], limit: [7]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 73 69 64 69 6f 74 2e 00 00 00 00 00 00 00 00 00 |sidiot..........|
+--------+-------------------------------------------------+----------------+
22:36:30 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - connected... /127.0.0.1:54687
22:36:30 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - before register /127.0.0.1:54687
22:36:30 [DEBUG] [Boss] c.s.n.c.MultiThreadServer - after register /127.0.0.1:54687
22:36:30 [DEBUG] [worker-0] c.s.n.c.MultiThreadServer - read... /127.0.0.1:54687
+--------+-------------------- all ------------------------+----------------+
position: [0], limit: [7]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 73 69 64 69 6f 74 2e 00 00 00 00 00 00 00 00 00 |sidiot..........|
+--------+-------------------------------------------------+----------------+
后记
以上就是 多线程优化 的所有内容了,心愿本篇博文对大家有所帮忙!
参考:
- Netty API reference;
- 黑马程序员 Netty 全套教程;
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