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Java网关服务-AIO（三）

概述

前两节中，我们已经获取了body的总长度，剩下的就是读出body，处理请求

ChannelServerHandler

ChannelServerHandler即从channel中读取请求，也向channle输出结果，因此它实现了InboundHandler, OutboundHandler

/**
 * 读取请求的内容，业务处理
 */
public class ChannelServerHandler implements CompletionHandler<Integer, ByteBuffer>, InboundHandler, OutboundHandler {

	private final static Logger LOGGER = LoggerFactory.getLogger(ChannelServerHandler.class);

	private AsynchronousSocketChannel channel;

	public ChannelServerHandler(AsynchronousSocketChannel channel) {
		this.channel = channel;
	}

	public void completed(Integer result, ByteBuffer attachment) {
		//如果条件成立，说明客户端主动终止了TCP套接字，这时服务端终止就可以了
		if (result == -1) {
			System.out.println("remote is close");
			closeChannel();
			return;
		}

		Object resultData;
		String req = (String) read(channel, attachment);
		if (req == null) {
			closeChannel();
			return;
		}

		try {
			LOGGER.info("socket:{}", channel.getRemoteAddress());

			//同步处理请求
			RequestHandler requestHandler = ApplicationUtils.getBean(RequestHandler.class);
			resultData = requestHandler.execute(req);

		} catch (Throwable t) {
			resultData = Result.error("ERROR", Utils.error(t));
			LOGGER.error("调用接口失败", t);
		}

		if (resultData == null) {
			resultData = Result.failure("FAILURE", "调用失败,数据为空.");
		}
		try {
			String resultContent =  resultData instanceOf String ? (String) resultData : JSON.toJSONString(resultData);
			byte[] bytes = resultContent.getBytes("UTF-8");
			ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
			writeBuffer.put(bytes);
			writeBuffer.flip();

			write(channel, writeBuffer);
		} catch (Exception e) {
			LOGGER.error("对象转JSON失败,对象:{}", resultData, e);
		}

		closeChannel();
	}

	@Override
	public Object read(AsynchronousSocketChannel socketChannel, ByteBuffer in) {
		in.flip();
		byte[] body = new byte[in.remaining()];
		in.get(body);

		String req = null;
		try {
			req = new String(body, "UTF-8");
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		return req;
	}

	@Override
	public Object write(AsynchronousSocketChannel socketChannel, ByteBuffer out) {
		//write，write操作结束后关闭通道
		channel.write(out, out, new CompletionHandler<Integer, ByteBuffer>() {
			@Override
			public void completed(Integer result, ByteBuffer attachment) {
				closeChannel();
			}

			@Override
			public void failed(Throwable exc, ByteBuffer attachment) {
				closeChannel();
			}
		});
		return null;
	}

	public void failed(Throwable exc, ByteBuffer attachment) {
		closeChannel();
	}

	private void closeChannel() {
		try {
			this.channel.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

读取body

in.flip();
		byte[] body = new byte[in.remaining()];
		in.get(body);

		String req = null;
		try {
			req = new String(body, "UTF-8");
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		return req;

in.remaining()

buffer中含有的字节数

客户端、服务端由于跨语言和经验问题，没有使用复杂的跨语言序列化技术，双方约定使用UTF-8编码，通过将body转换为String，最终获得了客户端传递的字符串。

处理请求

经过自定义的请求处理逻辑，同步处理，最终将响应编码后，发送给客户端，write操作结束后，关闭连接

总结

使用AIO开发服务端时，主要涉及

• 配置I/O事件完成的回调线程池
• 从accept -> read 到 向client端响应 write -> close,尽量使用CompletionHanlder来异步处理，不要在处理某个事件完成的线程中，同步的调用，如future.get()
• 如果是短连接，则需在write操作时注册write结束后的handler，在handler中关闭连接

扩展

长连接该如何处理

• 长连接意味着client可以发多次请求，由于多次请求被server执行的顺序是不可控的，可能后发的请求先响应，因此需要在请求和响应时，加requestId，据此对应到请求的结果
• 长连接不需要在write后关闭连接
• 长连接需要开发定时的ping-pong心跳消息
• 长连接在响应时比现在更复杂，也需要一个和请求类似或相同的协议来标识body长度

测试

测试用例

/**
	 * mvn -Dtest=com.jd.jshop.web.sdk.test.ClientTest#pingReqSocket test
	 *
	 * @throws IOException
	 */
	@Test
	@PerfTest(invocations = 20000, threads = 50)
	public void pingReqSocket() throws IOException {
		
		byte[] content = "ping".getBytes("UTF-8");
		String result = sendReq(content);

		//断言 是否和预期一致
		Assert.assertEquals("pong", result);
	}

	private String sendReq(byte[] content) throws IOException {
		ByteBuffer writeBuffer = ByteBuffer.allocate(4 + content.length);
		writeBuffer.putInt(content.length);
		writeBuffer.put(content);
		writeBuffer.flip();


		Socket socket = new Socket();
		socket.connect(new InetSocketAddress("127.0.0.1", 9801));
		socket.getOutputStream().write(writeBuffer.array());
		socket.getOutputStream().flush();
		byte[] buf = new byte[1024];
		int len = 0;
		String result = null;
		while ((len = socket.getInputStream().read(buf)) != -1) {
			result = new String(buf, 0, len);
			System.out.println(result);
		}
		return result;
	}

测试的方法是，在服务器上建立socket连接，向server发送ping，server返回pong
测试服务器：centos, 2个物理核，4个逻辑核，内存16G

分析aio的实现：
在ping-pong测试中性能极高，优于并甩开netty

以下是使用Netty开发的server端的测试用例，可以和上面的图片对比一下

Measured invocations:	10,000	
Thread Count:	10	
		 
	Measured
(system)	Required
Execution time:	1,646 ms	
Throughput:	6,075 / s	
Min. latency:	0 ms	
Average latency:	1 ms	
Median:	2 ms	
90%:	2 ms	
Max latency:	26 ms	

============================


Started at:	Oct 16, 2018 5:27:03 PM
Measured invocations:	20,000	
Thread Count:	20	
		 
	Measured
(system)	Required
Execution time:	3,293 ms	
Throughput:	6,073 / s	
Min. latency:	0 ms	
Average latency:	3 ms	
Median:	3 ms	
90%:	5 ms	
Max latency:	54 ms	

============================

Started at:	Oct 16, 2018 5:28:24 PM
Measured invocations:	20,000	
Thread Count:	10	
		 
	Measured
(system)	Required
Execution time:	3,051 ms	
Throughput:	6,555 / s	
Min. latency:	0 ms	
Average latency:	1 ms	
Median:	1 ms	
90%:	2 ms	
Max latency:	44 ms	

============================

Started at:	Oct 16, 2018 5:30:06 PM
Measured invocations:	20,000	
Thread Count:	50	
		 
	Measured
(system)	Required
Execution time:	3,167 ms	
Throughput:	6,315 / s	
Min. latency:	0 ms	
Average latency:	7 ms	
Median:	7 ms	
90%:	10 ms	
Max latency:	64 ms

分析基于Netty的实现：
吞吐量：6000+/s
10个线程时：90%低于2ms,平均1ms
20个线程时：90%低于5ms，平均3ms
50个线程时：90%低于10ms，平均7ms

线程越多，性能越低

当前测试用例不太依赖内存
执行10000+次请求，建立10000+连接，要求服务器对单个进程fd限制打开,防止报too many open files导致测试用例执行失败

ulimit -n 20240