netty中epoll server和nio server的使用
netty中epoll server和nio server的使用这几天有空研究了下netty中的EpollEventLoopGroup和NioEventLoopGroup的用法,在编码上没有显著的不同,对应的epoll,有一套的api供于使用,但是因为只能在linux机上使用,因此又借助了docker运行linux容器来运行相应程序,这节就来具体的讲述下。nio server编写了一个简单的Hel
netty中epoll server和nio server的使用
这几天有空研究了下netty中的EpollEventLoopGroup和NioEventLoopGroup的用法,在编码上没有显著的不同,对应的epoll,有一套的api供于使用,但是因为只能在linux机上使用,因此又借助了docker运行linux容器来运行相应程序,这节就来具体的讲述下。
nio server
编写了一个简单的Hello world的http server,不讲述详细代码了,只讲下最后的server中的部分源码,我采用的netty的版本是netty 4.0的,在这就不再使用netty5了,netty5因为一些更为复杂的特性和没有显著的提高性能已经被放弃了,这里就不再提了。
HttpHelloWorldServerHandler:
package cn.com.epoll;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.*;
import io.netty.util.AsciiString;
/**
* Created by xiaxuan on 17/11/14.
*/
public class HttpHelloWorldServerHandler extends ChannelInboundHandlerAdapter {
private static final byte[] CONTENT = { 'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd'};
private static final AsciiString CONTENT_TYPE = new AsciiString("Content-Type");
private static final AsciiString CONTENT_LENGTH = new AsciiString("Content-Length");
private static final AsciiString CONNECTION = new AsciiString("Connection");
private static final AsciiString KEEP_ALIVE = new AsciiString("keep-alive");
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof HttpRequest) {
HttpRequest req = (HttpRequest) msg;
if (HttpUtil.is100ContinueExpected(req)) {
ctx.write(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE));
}
boolean keepAlive = HttpUtil.isKeepAlive(req);
FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, Unpooled.wrappedBuffer(CONTENT));
response.headers().set(CONTENT_TYPE, "text/plain");
response.headers().set(CONTENT_LENGTH, response.content().readableBytes());
if (!keepAlive) {
ctx.write(response).addListener(ChannelFutureListener.CLOSE);
} else {
response.headers().set(CONNECTION, KEEP_ALIVE);
ctx.write(response);
}
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
channelRead的方法很简单,就是判断当前是不是http请求,是的话就输出Hello World,功能比较简单。
HttpHelloWorldServerInitializer:
public class HttpHelloWorldServerInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new HttpServerCodec());
ch.pipeline().addLast(new HttpHelloWorldServerHandler());
}
}
pipline添加Handler处理。
NioHttpHelloWorldServer:
package cn.com.epoll;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.PooledByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
/**
* Created by xiaxuan on 17/11/14.
*/
public class NioHttpHelloWorldServer {
private static final int PORT = Integer.parseInt(System.getProperty("port", "8080"));
public static void main(String[] args) {
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
ServerBootstrap b = new ServerBootstrap();
try {
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 1024)
.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT)
.childHandler(new HttpHelloWorldServerInitializer());
Channel ch = b.bind(PORT).channel();
ch.closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
普通的netty演示程序的写法,没什么特殊的,但是还是需要提一下其中使用的NioEventLoopGroup,NioEventLoopGroup就是一个简单的线程池调度服务,我们再追溯NioEventLoopGroup的源码的时候可以发现最终NioEventLoopGroup继承的就是ScheduledExecutorService,就是有多个NioEventLoop对象的线程池,如果不指定线程池的的容量的话,默认就是当前cpu * 2的数量,转到源码可以看到传入的构造函数为0,为以下:
* Create a new instance using the default number of threads, the default {@link ThreadFactory} and
* the {@link SelectorProvider} which is returned by {@link SelectorProvider#provider()}.
*/
public NioEventLoopGroup() {
this(0);
}
但是转到最终源码会发现当判断为0的时候,去了默认值,源码如下:
static {
DEFAULT_EVENT_LOOP_THREADS = Math.max(1, SystemPropertyUtil.getInt(
"io.netty.eventLoopThreads", NettyRuntime.availableProcessors() * 2));
if (logger.isDebugEnabled()) {
logger.debug("-Dio.netty.eventLoopThreads: {}", DEFAULT_EVENT_LOOP_THREADS);
}
}
/**
* @see MultithreadEventExecutorGroup#MultithreadEventExecutorGroup(int, Executor, Object...)
*/
protected MultithreadEventLoopGroup(int nThreads, Executor executor, Object... args) {
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, executor, args);
}
如上,最终取得默认值就是cpu * 2。
而这里最终还是需要提一下NioEventLoop,NioEventLoop的父类继承了SingleThreadEventExecutor,也是一个线程池调度服务,但是只有一个单线程,在NioEventLoop创建的时候,同时也会创建一个Selector,selector管理channel,所以实际上NioEventLoopGroup就是一组管理Channel的线程池。
源码解析就到此未知,运行程序,在web端请求的效果如下:
十分简单,这是nio server的运行。
epoll server
epoll server的源码主要在server上的不同,其他的与上相同,server如下:
package cn.com.epoll;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.PooledByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.epoll.EpollEventLoopGroup;
import io.netty.channel.epoll.EpollServerSocketChannel;
/**
* Created by xiaxuan on 17/11/14.
*/
public class HttpHelloWorldServer {
static final int PORT = Integer.parseInt(System.getProperty("port", "8080"));
public static void main(String[] args) {
EventLoopGroup bossGroup = new EpollEventLoopGroup(1);
EventLoopGroup workerGroup = new EpollEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.channel(EpollServerSocketChannel.class);
b.option(ChannelOption.SO_BACKLOG, 1024);
b.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
b.group(bossGroup, workerGroup)
.childHandler(new HttpHelloWorldServerInitializer());
Channel ch = b.bind(PORT).sync().channel();
ch.closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
暂时先不讲Epoll和nio selector特性的不同,首先先把这里的应用程序讲完,在普通的windows或者mac上运行当前的程序会运行不起来的,会报错为:
Exception in thread "main" java.lang.UnsatisfiedLinkError: failed to load the required native library
at io.netty.channel.epoll.Epoll.ensureAvailability(Epoll.java:78)
at io.netty.channel.epoll.EpollEventLoopGroup.<clinit>(EpollEventLoopGroup.java:38)
at cn.com.epoll.HttpHelloWorldServer.main(HttpHelloWorldServer.java:19)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.ExceptionInInitializerError
at io.netty.channel.epoll.Epoll.<clinit>(Epoll.java:33)
... 7 more
Caused by: java.lang.IllegalStateException: Only supported on Linux
at io.netty.channel.epoll.Native.loadNativeLibrary(Native.java:189)
at io.netty.channel.epoll.Native.<clinit>(Native.java:61)
... 8 more
epoll模型只有在linux kernel 2.6以上才能支持,在windows和mac都是不支持的,因此需要在linux上运行这个程序,但是本机是mac系统,因此不能在本地运行,然后本地也没有安装linux虚拟机,因此便借助了docker来使程序运行,于此同时为了方便运行maven打出的jar包,借助了一个maven插件以供打出一个可执行的jar包,插件如下:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.3</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>${exec.mainClass}</mainClass>
</transformer>
</transformers>
<artifactSet>
</artifactSet>
</configuration>
</execution>
</executions>
</plugin>
然后编写的Dockerfile文件如下:
FROM java:8
MAINTAINER bingwenwuhen bingwenwuhen@163.com
RUN mkdir /app
COPY target/epoll-server-1.0-SNAPSHOT.jar /app
ENTRYPOINT ["java", "-jar", "app/epoll-server-1.0-SNAPSHOT.jar"]
EXPOSE 8080
我拉取的这个java:8基础镜像就是以centos为基础镜像,因此就是linux环境,在可能一些基础镜像上并非支持epoll模型的可能性上,可以直接拉取centos镜像,然后配置java环境等等,在此不再详述,这个在网上有着足够的资料。
在maven编译打包之后,docker进行镜像构建,运行,最后执行docker ps命令,查看容器运行情况,如下:
容器正常运行,使用curl命令请求服务,将会获取如上一样的结果,epoll server正常运行。
我们在查看EpollEventLoopGroup源码的时候可以发现,NioEventLoopGroup和EpollEventgroup最终继承的类都是相同,只是部分特性不同而已,因此在这就不再讲述EpollEventLoopGroup的源码,然而epoll模型本身讲述起来又相当复杂,不是本节能够讲述清楚的,对于EpollEventLoopGroup与epoll模型,以后有空再做专题详述。
源码下载地址
NioEventLoopGroup的源码下载地址就不再给出,下面是epoll server的源码下载地址:
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