- 与老版本区别
- RPC框架架构
- 组件详细功能说明
- TransportContext
- TransportConf
- TransportClientFactory
- TransportClientBootstrap
- 创建客户端TransportClient
- TransportClient
- TransportServer
- TransportChannelHandler
- ManagedBuffer
- TransportServerBootstrap
- RpcHandler
在Spark 0.x.x与Spark 1.x.x版本中，组件间的消息通信主要借助于Akka。但是Akka在Spark 2.0.0版本中被移除了
在Spark 1.x.x版本中，用户文件与Jar包的上传采用了由Jetty实现的HttpFileServer，但在Spark 2.0.0版本中也被废弃了，现在使用的是基于Spark内置RPC框架的NettyStreamManager。
RPC框架架构TransportContext内部包含传输上下文的配置信息TransportConf和对客户端请求消息进行处理的RpcHandler。
TransportConf在创建TransportClientFactory和TransportServer时都是必须的
TransportClientFactory是RPC客户端的工厂类。
TransportServer是RPC服务端的实现。
组件详细功能说明
TransportContext：传输上下文，包含了用于创建传输服务端（TransportServer）和传输客户端工厂（TransportClientFactory）的上下文信息，并支持使用TransportChannelHandler设置Netty提供的SocketChannel的Pipeline的实现。
TransportConf：传输上下文的配置信息。
RpcHandler：对调用传输客户端（TransportClient）的sendRPC方法发送的消息进行处理的程序。
MessageEncoder：在将消息放入管道前，先对消息内容进行编码，防止管道另一端读取时丢包和解析错误。
MessageDecoder：对从管道中读取的ByteBuf进行解析，防止丢包和解析错误；
TransportFrameDecoder：对从管道中读取的ByteBuf按照数据帧进行解析；
RpcResponseCallback：RpcHandler对请求的消息处理完毕后，进行回调的接口。
TransportClientFactory：创建传输客户端（TransportClient）的传输客户端工厂类。
ClientPool：在两个对等节点间维护的关于传输客户端（TransportClient）的池子。ClientPool是TransportClientFactory的内部组件。
TransportClient：RPC框架的客户端，用于获取预先协商好的流中的连续块。TransportClient旨在允许有效传输大量数据，这些数据将被拆分成几百KB到几MB的块。当TransportClient处理从流中获取的获取的块时，实际的设置是在传输层之外完成的。sendRPC方法能够在客户端和服务端的同一水平线的通信进行这些设置。
TransportClientBootstrap：当服务端响应客户端连接时在客户端执行一次的引导程序。
TransportRequestHandler：用于处理客户端的请求并在写完块数据后返回的处理程序。
TransportResponseHandler：用于处理服务端的响应，并且对发出请求的客户端进行响应的处理程序。
TransportChannelHandler：代理由TransportRequestHandler处理的请求和由TransportResponseHandler处理的响应，并加入传输层的处理。
TransportServerBootstrap：当客户端连接到服务端时在服务端执行一次的引导程序。
TransportServer：RPC框架的服务端，提供高效的、低级别的流服务。
先上UML图
可用看到成员变量比较重要的TransportConf和rpcHandler都在里面，此外MessageEncoder，MessageDecoder也能找到。
然后比较重要的方法是createServer和createClientFactory创建服务端和客户端
public class TransportContext {
private static final Logger logger = LoggerFactory.getLogger(TransportContext.class);
private final TransportConf conf;
private final RpcHandler rpcHandler;
private final boolean closeIdleConnections;
private static final MessageEncoder ENCODER = MessageEncoder.INSTANCE;
private static final MessageDecoder DECODER = MessageDecoder.INSTANCE;
public class TransportConf {
private final ConfigProvider conf;
private final String module;
真实的配置由ConfigProvider提供，ConfigProvider是一个抽象类
public abstract class ConfigProvider {
public abstract String get(String name);
public abstract Iterable<Map.Entry<String, String>> getAll();
public String get(String name, String defaultValue) {
try {
return get(name);
} catch (NoSuchElementException e) {
return defaultValue;
}
}
Spark通常使用SparkTransportConf创建TransportConf
object SparkTransportConf {
private val MAX_DEFAULT_NETTY_THREADS = 8
def fromSparkConf(_conf: SparkConf, module: String, numUsableCores: Int = 0): TransportConf = {
val conf = _conf.clone
val numThreads = defaultNumThreads(numUsableCores)
conf.setIfMissing(s"spark.$module.io.serverThreads", numThreads.toString)
conf.setIfMissing(s"spark.$module.io.clientThreads", numThreads.toString)
new TransportConf(module, new ConfigProvider {
override def get(name: String): String = conf.get(name)
override def get(name: String, defaultValue: String): String = conf.get(name, defaultValue)
override def getAll(): java.lang.Iterable[java.util.Map.Entry[String, String]] = {
conf.getAll.toMap.asJava.entrySet()
}
})
}
private def defaultNumThreads(numUsableCores: Int): Int = {
//如果numUsableCores小于等于0，那么线程数是系统可用处理器的数量，不过系统的内核数不可能全部用于网络传输使用，所以这里还将分配给网络传输的内核数量最多限制在8个
val availableCores =
if (numUsableCores > 0) numUsableCores else Runtime.getRuntime.availableProcessors()
math.min(availableCores, MAX_DEFAULT_NETTY_THREADS)
}
}
可用看到其实也是调用了，之前说到底sparkConf的clone方法，拷贝spark属性,并且实现了ConfigProvider的几个抽象方法。
TransportClientFactorypublic TransportClientFactory createClientFactory(List<TransportClientBootstrap> bootstraps) {
return new TransportClientFactory(this, bootstraps);
}
public TransportClientFactory createClientFactory() {
return createClientFactory(new ArrayList<>());
}
TransportContext创建TransportClientFactory的方法
private final TransportContext context;
private final TransportConf conf;
private final List<TransportClientBootstrap> clientBootstraps;
//一个socketAddress对应一个ClientPool里面包含多个TransportClient
private final ConcurrentHashMap<SocketAddress, ClientPool> connectionPool;
/** Random number generator for picking connections between peers. */
private final Random rand;
private final int numConnectionsPerPeer;
private final Class<? extends Channel> socketChannelClass;
private EventLoopGroup workerGroup;
private PooledByteBufAllocator pooledAllocator;
private final NettyMemoryMetrics metrics;
public TransportClientFactory(
TransportContext context,
List<TransportClientBootstrap> clientBootstraps) {
this.context = Preconditions.checkNotNull(context);
this.conf = context.getConf();
this.clientBootstraps = Lists.newArrayList(Preconditions.checkNotNull(clientBootstraps));
this.connectionPool = new ConcurrentHashMap<>();
this.numConnectionsPerPeer = conf.numConnectionsPerPeer();
this.rand = new Random();
IOMode ioMode = IOMode.valueOf(conf.ioMode());
this.socketChannelClass = NettyUtils.getClientChannelClass(ioMode);
this.workerGroup = NettyUtils.createEventLoop(
ioMode,
conf.clientThreads(),
conf.getModuleName() + "-client");
this.pooledAllocator = NettyUtils.createPooledByteBufAllocator(
conf.preferDirectBufs(), false, conf.clientThreads());
this.metrics = new NettyMemoryMetrics(
this.pooledAllocator, conf.getModuleName() + "-client", conf);
}
TransportClientFactory的构造方法
相关变量解释：
clientBootstraps：即参数传递的TransportClientBootstrap列表；
connectionPool：即针对每个Socket地址的连接池ClientPool的缓存；connectionPool的数据结构较为复杂
numConnectionsPerPeer：即从TransportConf获取的key为”spark.+模块名+.io.numConnectionsPerPeer”的属性值。此属性值用于指定对等节点间的连接数。这里的模块名实际为TransportConf的module字段，Spark的很多组件都利用RPC框架构建，它们之间按照模块名区分，例如RPC模块的key为“spark.rpc.io.numConnectionsPerPeer”；
rand：对Socket地址对应的连接池ClientPool中缓存的TransportClient进行随机选择，对每个连接做负载均衡；
ioMode：IO模式，即从TransportConf获取key为”spark.+模块名+.io.mode”的属性值。默认值为NIO，Spark还支持EPOLL；
socketChannelClass：客户端Channel被创建时使用的类，通过ioMode来匹配，默认为NioSocketChannel，Spark还支持EpollEventLoopGroup；
workerGroup：根据Netty的规范，客户端只有worker组，所以此处创建workerGroup。workerGroup的实际类型是NioEventLoopGroup；
pooledAllocator ：汇集ByteBuf但对本地线程缓存禁用的分配器。
public static EventLoopGroup createEventLoop(IOMode mode, int numThreads, String threadPrefix) {
ThreadFactory threadFactory = createThreadFactory(threadPrefix);
switch (mode) {
case NIO:
return new NioEventLoopGroup(numThreads, threadFactory);
case EPOLL:
return new EpollEventLoopGroup(numThreads, threadFactory);
default:
throw new IllegalArgumentException("Unknown io mode: " + mode);
}
}
NettySocketChannel性能上从低到高如下：
- OioSocketChannel：传统，阻塞式编程。
- NioSocketChannel：select/poll或者epoll，jdk 7之后linux下会自动选择epoll。
- EpollSocketChannel：epoll，仅限linux，提供更多额外选项。
- EpollDomainSocketChannel：ipc模式，仅限客户端、服务端在相同主机的情况，从4.0.26版本开始支持
public interface TransportClientBootstrap {
void doBootstrap(TransportClient client, Channel channel) throws RuntimeException;
}
TransportClientBootstrap是在TransportClient上执行的客户端引导程序，主要对连接建立时进行一些初始化的准备（例如验证、加密）。TransportClientBootstrap所作的 *** 作往往是昂贵的，好在建立的连接可以重用。
三个实现类，我们以EncryptionDisablerBootstrap为例看看具体做了啥
private static class EncryptionDisablerBootstrap implements TransportClientBootstrap {
@Override
public void doBootstrap(TransportClient client, Channel channel) {
channel.pipeline().remove(SaslEncryption.ENCRYPTION_HANDLER_NAME);
}
}
作用是移除客户端管道中的SASL加密
创建客户端TransportClientpublic class TransportClientFactory implements Closeable {
/** A simple data structure to track the pool of clients between two peer nodes. */
private static class ClientPool {
TransportClient[] clients;
Object[] locks;
ClientPool(int size) {
clients = new TransportClient[size];
locks = new Object[size];
for (int i = 0; i < size; i++) {
locks[i] = new Object();
}
}
}
ClientPool实际是由TransportClient的数组构成，而locks数组中的Object与clients数组中的TransportClient按照数组索引一一对应，通过对每个TransportClient分别采用不同的锁，降低并发情况下线程间对锁的争用，进而减少阻塞，提高并发度。
public TransportClient createClient(String remoteHost, int remotePort)
throws IOException, InterruptedException {
final InetSocketAddress unresolvedAddress =
InetSocketAddress.createUnresolved(remoteHost, remotePort);
// Create the ClientPool if we don't have it yet.
//判断是否存在了指定端口的客户端池
ClientPool clientPool = connectionPool.get(unresolvedAddress);
if (clientPool == null) {
//numConnectionsPerPeer是transportContext中拿过来的，还记得默认是取系统cpu和8较小者
//connectionPool
connectionPool.putIfAbsent(unresolvedAddress, new ClientPool(numConnectionsPerPeer));
clientPool = connectionPool.get(unresolvedAddress);
}
int clientIndex = rand.nextInt(numConnectionsPerPeer);
TransportClient cachedClient = clientPool.clients[clientIndex];
//判断client是否初始化了,且处于激活状态，更新handler访问时间并返回TransportClient
if (cachedClient != null && cachedClient.isActive()) {
TransportChannelHandler handler = cachedClient.getChannel().pipeline()
.get(TransportChannelHandler.class);
synchronized (handler) {
handler.getResponseHandler().updateTimeOfLastRequest();
}
if (cachedClient.isActive()) {
logger.trace("Returning cached connection to {}: {}",
cachedClient.getSocketAddress(), cachedClient);
return cachedClient;
}
}
final long preResolveHost = System.nanoTime();
final InetSocketAddress resolvedAddress = new InetSocketAddress(remoteHost, remotePort);
final long hostResolveTimeMs = (System.nanoTime() - preResolveHost) / 1000000;
if (hostResolveTimeMs > 2000) {
logger.warn("DNS resolution for {} took {} ms", resolvedAddress, hostResolveTimeMs);
} else {
logger.trace("DNS resolution for {} took {} ms", resolvedAddress, hostResolveTimeMs);
}
//加锁
synchronized (clientPool.locks[clientIndex]) {
cachedClient = clientPool.clients[clientIndex];
//双重验证
if (cachedClient != null) {
if (cachedClient.isActive()) {
logger.trace("Returning cached connection to {}: {}", resolvedAddress, cachedClient);
return cachedClient;
} else {
logger.info("Found inactive connection to {}, creating a new one.", resolvedAddress);
}
}
//最后调用createClient(resolvedAddress)创建TransportClient
clientPool.clients[clientIndex] = createClient(resolvedAddress);
return clientPool.clients[clientIndex];
}
}
createClient(String remoteHost, int remotePort)方法主要做的事情是通过unresolvedAddress去connectionPool中查找地址对应的clientPool，没有则创建,再随机取其中一个client如果说客户端不为空。更新handler最后访问时间，没有则调用createClient(InetSocketAddress address)创建TransportClient。
private TransportClient createClient(InetSocketAddress address)
throws IOException, InterruptedException {
logger.debug("Creating new connection to {}", address);
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(workerGroup)
.channel(socketChannelClass)
.option(ChannelOption.TCP_NODELAY, true)
.option(ChannelOption.SO_KEEPALIVE, true)
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, conf.connectionTimeoutMs())
.option(ChannelOption.ALLOCATOR, pooledAllocator);
if (conf.receiveBuf() > 0) {
bootstrap.option(ChannelOption.SO_RCVBUF, conf.receiveBuf());
}
if (conf.sendBuf() > 0) {
bootstrap.option(ChannelOption.SO_SNDBUF, conf.sendBuf());
}
final AtomicReference<TransportClient> clientRef = new AtomicReference<>();
final AtomicReference<Channel> channelRef = new AtomicReference<>();
bootstrap.handler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) {
//客户端实际的创建地址
TransportChannelHandler clientHandler = context.initializePipeline(ch);
clientRef.set(clientHandler.getClient());
channelRef.set(ch);
}
});
// Connect to the remote server
long preConnect = System.nanoTime();
ChannelFuture cf = bootstrap.connect(address);
if (!cf.await(conf.connectionTimeoutMs())) {
throw new IOException(
String.format("Connecting to %s timed out (%s ms)", address, conf.connectionTimeoutMs()));
} else if (cf.cause() != null) {
throw new IOException(String.format("Failed to connect to %s", address), cf.cause());
}
TransportClient client = clientRef.get();
Channel channel = channelRef.get();
assert client != null : "Channel future completed successfully with null client";
long preBootstrap = System.nanoTime();
logger.debug("Connection to {} successful, running bootstraps...", address);
try {
//使用clientBootstrap加工channel
for (TransportClientBootstrap clientBootstrap : clientBootstraps) {
clientBootstrap.doBootstrap(client, channel);
}
}
return client;
createClient(InetSocketAddress address)其实就是使用nettyApi与服务端创建sockt连接clientRef存储TransportClient实例，channelRef存储socktChannel实例
public TransportChannelHandler initializePipeline(
SocketChannel channel,
RpcHandler channelRpcHandler) {
try {
TransportChannelHandler channelHandler = createChannelHandler(channel, channelRpcHandler);
channel.pipeline()
.addLast("encoder", ENCODER)
.addLast(TransportFrameDecoder.HANDLER_NAME, NettyUtils.createFrameDecoder())
.addLast("decoder", DECODER)
//Netty的IdleStateHandler心跳机制主要是用来检测远端是否存活，如果不存活或活跃则对空闲Socket连接进行处理避免资源的浪费；
.addLast("idleStateHandler", new IdleStateHandler(0, 0, conf.connectionTimeoutMs() / 1000))
.addLast("handler", channelHandler);
return channelHandler;
} catch (RuntimeException e) {
logger.error("Error while initializing Netty pipeline", e);
throw e;
}
}
TransportChannelHandler clientHandler = context.initializePipeline(ch);最终netty底层的 *** 作，ENCODER,DECODER等一些 *** 作都在这里做的，TransportChannelHandler才是更加定制的一些 *** 作
private TransportChannelHandler createChannelHandler(Channel channel, RpcHandler rpcHandler) {
TransportResponseHandler responseHandler = new TransportResponseHandler(channel);
TransportClient client = new TransportClient(channel, responseHandler);
TransportRequestHandler requestHandler = new TransportRequestHandler(channel, client,
rpcHandler, conf.maxChunksBeingTransferred());
//client客户端requestHandler请求处理器,responseHandler返回处理器
return new TransportChannelHandler(client, responseHandler, requestHandler,
conf.connectionTimeoutMs(), closeIdleConnections);
}
上面TransportChannelHandler的创建过程，requestHandler请求处理器,responseHandler返回处理器的职责后面有机会再分析。
*TransportClient在创建时持有的都是TransportResponseHandler
TransportClientpublic TransportClient(Channel channel, TransportResponseHandler handler) {
this.channel = Preconditions.checkNotNull(channel);
this.handler = Preconditions.checkNotNull(handler);
this.timedOut = false;
}
TransportClient一共有五个方法用于发送请求，分别为：
fetchChunk：从远端协商好的流中请求单个块；
stream：使用流的ID，从远端获取流数据；
sendRpc：向服务端发送RPC的请求，通过At least Once Delivery原则保证请求不会丢失；
sendRpcSync：向服务端发送异步的RPC的请求，并根据指定的超时时间等待响应；
send：向服务端发送RPC的请求，但是并不期望能获取响应，因而不能保证投递的可靠性；
public TransportServer createServer(
String host, int port, List<TransportServerBootstrap> bootstraps) {
return new TransportServer(this, host, port, rpcHandler, bootstraps);
}
/** Creates a new server, binding to any available ephemeral port. */
public TransportServer createServer(List<TransportServerBootstrap> bootstraps) {
return createServer(0, bootstraps);
}
public TransportServer createServer() {
return createServer(0, new ArrayList<>());
}
最终都是调用TransportServer createServer(String host, int port, List bootstraps)
public TransportServer(
TransportContext context,
String hostToBind,
int portToBind,
RpcHandler appRpcHandler,
List<TransportServerBootstrap> bootstraps) {
this.context = context;
this.conf = context.getConf();
this.appRpcHandler = appRpcHandler;
this.bootstraps = Lists.newArrayList(Preconditions.checkNotNull(bootstraps));
boolean shouldClose = true;
try {
init(hostToBind, portToBind);
shouldClose = false;
} finally {
if (shouldClose) {
JavaUtils.closeQuietly(this);
}
}
}
TransportServer的构造器中的各个变量分别为：
context：即参数传递的TransportContext的引用；
conf：即TransportConf，这里通过调用TransportContext的getConf获取；
appRpcHandler：即RPC请求处理器RpcHandler；
bootstraps：即参数传递的TransportServerBootstrap列表；
private void init(String hostToBind, int portToBind) {
IOMode ioMode = IOMode.valueOf(conf.ioMode());
EventLoopGroup bossGroup = NettyUtils.createEventLoop(ioMode, 1,
conf.getModuleName() + "-boss");
EventLoopGroup workerGroup = NettyUtils.createEventLoop(ioMode, conf.serverThreads(),
conf.getModuleName() + "-server");
PooledByteBufAllocator allocator = NettyUtils.createPooledByteBufAllocator(
conf.preferDirectBufs(), true /* allowCache */, conf.serverThreads());
bootstrap = new ServerBootstrap()
.group(bossGroup, workerGroup)
.channel(NettyUtils.getServerChannelClass(ioMode))
.option(ChannelOption.ALLOCATOR, allocator)
.option(ChannelOption.SO_REUSEADDR, !SystemUtils.IS_OS_WINDOWS)
.childOption(ChannelOption.ALLOCATOR, allocator);
this.metrics = new NettyMemoryMetrics(
allocator, conf.getModuleName() + "-server", conf);
if (conf.backLog() > 0) {
bootstrap.option(ChannelOption.SO_BACKLOG, conf.backLog());
}
if (conf.receiveBuf() > 0) {
bootstrap.childOption(ChannelOption.SO_RCVBUF, conf.receiveBuf());
}
if (conf.sendBuf() > 0) {
bootstrap.childOption(ChannelOption.SO_SNDBUF, conf.sendBuf());
}
bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) {
RpcHandler rpcHandler = appRpcHandler;
for (TransportServerBootstrap bootstrap : bootstraps) {
rpcHandler = bootstrap.doBootstrap(ch, rpcHandler);
}
context.initializePipeline(ch, rpcHandler);
}
});
InetSocketAddress address = hostToBind == null ?
new InetSocketAddress(portToBind): new InetSocketAddress(hostToBind, portToBind);
channelFuture = bootstrap.bind(address);
channelFuture.syncUninterruptibly();
port = ((InetSocketAddress) channelFuture.channel().localAddress()).getPort();
logger.debug("Shuffle server started on port: {}", port);
}
1.创建bossGroup和workerGroup（根据Netty的API文档，Netty服务端需同时创建bossGroup和workerGroup。）；
2.创建一个汇集ByteBuf但对本地线程缓存禁用的分配器；
3.调用Netty的API创建Netty的服务端根引导程序并对其进行配置；
4.为根引导程序设置管道初始化回调函数，此回调函数首先设置TransportServerBootstrap到根引导程序中，然后调用TransportContext的initializePipeline方法初始化Channel的pipeline；
5.给根引导程序绑定Socket的监听端口，最后返回监听的端口。
context.initializePipeline方法上面有说明，核心干的事ENCODER,DECODER等一些 *** 作都在这里做的，然后加上TransportChannelHandler channelHandler = createChannelHandler(channel, channelRpcHandler);
TransportChannelHandlerpublic class TransportChannelHandler extends ChannelInboundHandlerAdapter {
其实继承了ChannelInboundHandler重点关心TransportChannelHandler实现的channelRead
@Override
public void channelRead(ChannelHandlerContext ctx, Object request) throws Exception {
if (request instanceof RequestMessage) {
requestHandler.handle((RequestMessage) request);
} else if (request instanceof ResponseMessage) {
responseHandler.handle((ResponseMessage) request);
} else {
ctx.fireChannelRead(request);
}
}
当TransportChannelHandler读取到的request是RequestMessage类型时，则将此消息的处理进一步交给TransportRequestHandler，当request是ResponseMessage时，则将此消息的处理进一步交给TransportResponseHandler。
public class TransportResponseHandler extends MessageHandler {
public class TransportRequestHandler extends MessageHandler {
TransportRequestHandler与TransportResponseHandler都继承自抽象类MessageHandler
public abstract class MessageHandler<T extends Message> {
/** Handles the receipt of a single message. */
public abstract void handle(T message) throws Exception;
/** Invoked when the channel this MessageHandler is on is active. */
public abstract void channelActive();
/** Invoked when an exception was caught on the Channel. */
public abstract void exceptionCaught(Throwable cause);
/** Invoked when the channel this MessageHandler is on is inactive. */
public abstract void channelInactive();
}
MessageHandler定义了几个方法:
- handle：用于对接收到的单个消息进行处理；
- channelActive：当channel激活时调用；
- exceptionCaught：当捕获到channel发生异常时调用；
- channelInactive：当channel非激活时调用；
public interface Message extends Encodable {
/** Used to identify this request type. */
Type type();
/** An optional body for the message. */
ManagedBuffer body();
/** Whether to include the body of the message in the same frame as the message. */
boolean isBodyInFrame();
Message定义
public interface Encodable {
int encodedLength();
void encode(ByteBuf buf);
}
实现Encodable接口的类将可以转换到一个ByteBuf中，多个对象将被存储到预先分配的单个ByteBuf，所以这里的encodedLength用于返回转换的对象数量。
从图看到最终的消息实现类都直接或间接的实现了RequestMessage或ResponseMessage接口，其中RequestMessage的具体实现有四种，分别是：
ChunkFetchRequest：请求获取流的单个块的序列。
RpcRequest：此消息类型由远程的RPC服务端进行处理，是一种需要服务端向客户端回复的RPC请求信息类型。
OneWayMessage：此消息也需要由远程的RPC服务端进行处理，与RpcRequest不同的是不需要服务端向客户端回复。
StreamRequest：此消息表示向远程的服务发起请求，以获取流式数据。
由于OneWayMessage 不需要响应，所以ResponseMessage的对于成功或失败状态的实现各有三种，分别是：
ChunkFetchSuccess：处理ChunkFetchRequest成功后返回的消息；
ChunkFetchFailure：处理ChunkFetchRequest失败后返回的消息；
RpcResponse：处理RpcRequest成功后返回的消息；
RpcFailure：处理RpcRequest失败后返回的消息；
StreamResponse：处理StreamRequest成功后返回的消息；
StreamFailure：处理StreamRequest失败后返回的消息；
public abstract class ManagedBuffer {
具体属性代表的意义：
size：返回数据的字节数。
nioByteBuffer：将数据按照Nio的ByteBuffer类型返回。
createInputStream：将数据按照InputStream返回。
retain：当有新的使用者使用此视图时，增加引用此视图的引用数。
release：当有使用者不再使用此视图时，减少引用此视图的引用数。当引用数为0时释放缓冲区。
convertToNetty：将缓冲区的数据转换为Netty的对象，用来将数据写到外部。此方法返回的数据类型要么是io.netty.buffer.ByteBuf，要么是io.netty.channel.FileRegion。
Message的body方法返回的是ManagedBuffer;ManagedBuffer是一个抽象类。
具体的一些实现类。
TransportServerBootstrappublic interface TransportServerBootstrap {
RpcHandler doBootstrap(Channel channel, RpcHandler rpcHandler);
}
TransportServerBootstrap的doBootstrap方法将对服务端的RpcHandler进行代理，接收客户端的请求。TransportServerBootstrap有SaslServerBootstrap和EncryptionCheckerBootstrap两个实现类。
public RpcHandler doBootstrap(Channel channel, RpcHandler rpcHandler) {
return new SaslRpcHandler(conf, channel, rpcHandler, secretKeyHolder);
}
SaslServerBootstrap的doBootstrap实现
RpcHandlerpublic TransportChannelHandler initializePipeline(
SocketChannel channel,
RpcHandler channelRpcHandler) {
try {
TransportChannelHandler channelHandler = createChannelHandler(channel, channelRpcHandler);
channel.pipeline()
.addLast("encoder", ENCODER)
.addLast(TransportFrameDecoder.HANDLER_NAME, NettyUtils.createFrameDecoder())
.addLast("decoder", DECODER)
.addLast("idleStateHandler", new IdleStateHandler(0, 0, conf.connectionTimeoutMs() / 1000))
// NOTE: Chunks are currently guaranteed to be returned in the order of request, but this
// would require more logic to guarantee if this were not part of the same event loop.
.addLast("handler", channelHandler);
return channelHandler;
} catch (RuntimeException e) {
logger.error("Error while initializing Netty pipeline", e);
throw e;
}
}
客户端和服务端的创建都用到了TransportContext.initializePipeline而里面需要传入RpcHandler rpcHandler;
private TransportChannelHandler createChannelHandler(Channel channel, RpcHandler rpcHandler) {
TransportResponseHandler responseHandler = new TransportResponseHandler(channel);
TransportClient client = new TransportClient(channel, responseHandler);
TransportRequestHandler requestHandler = new TransportRequestHandler(channel, client,
rpcHandler, conf.maxChunksBeingTransferred());
return new TransportChannelHandler(client, responseHandler, requestHandler,
conf.connectionTimeoutMs(), closeIdleConnections);
}
注意到requestHandler在创建时用到了rpcHandler。其实requestHandler相当于是代理了rpcHandler。所以有必要研究一下RpcHandler。因为client只是使用到的responseHandler而它在创建时与rpcHandler无关。所以其实rpcHandler只对服务端创建有影响
public abstract class RpcHandler {
private static final RpcResponseCallback ONE_WAY_CALLBACK = new OneWayRpcCallback();
public abstract void receive(
TransportClient client,
ByteBuffer message,
RpcResponseCallback callback);
public StreamCallbackWithID receiveStream(
TransportClient client,
ByteBuffer messageHeader,
RpcResponseCallback callback) {
throw new UnsupportedOperationException();
}
public abstract StreamManager getStreamManager();
public void receive(TransportClient client, ByteBuffer message) {
receive(client, message, ONE_WAY_CALLBACK);
}
public void channelActive(TransportClient client) { }
public void channelInactive(TransportClient client) { }
public void exceptionCaught(Throwable cause, TransportClient client) { }
private static class OneWayRpcCallback implements RpcResponseCallback {
private static final Logger logger = LoggerFactory.getLogger(OneWayRpcCallback.class);
@Override
public void onSuccess(ByteBuffer response) {
logger.warn("Response provided for one-way RPC.");
}
@Override
public void onFailure(Throwable e) {
logger.error("Error response provided for one-way RPC.", e);
}
}
}
RpcHandler是一个抽象类，各个方法的做用：
receive：这是一个抽象方法，用来接收单一的RPC消息，具体处理逻辑需要子类去实现。
channelActive：当与给定客户端相关联的channel处于活动状态时调用。
channelInactive：当与给定客户端相关联的channel处于非活动状态时调用。
exceptionCaught：当channel产生异常时调用。
getStreamManager：获取StreamManager，StreamManager可以从流中获取单个的块，因此它也包含着当前正在被TransportClient获取的流的状态。
最后讲一下requestHandler的handle方法,前面已经强调过了requestHandler是在服务端使用的
public void handle(RequestMessage request) {
if (request instanceof ChunkFetchRequest) {
processFetchRequest((ChunkFetchRequest) request);
} else if (request instanceof RpcRequest) {
processRpcRequest((RpcRequest) request);
} else if (request instanceof OneWayMessage) {
processOneWayMessage((OneWayMessage) request);
} else if (request instanceof StreamRequest) {
processStreamRequest((StreamRequest) request);
} else if (request instanceof UploadStream) {
processStreamUpload((UploadStream) request);
} else {
throw new IllegalArgumentException("Unknown request type: " + request);
}
}
可用看到针对不同类型的请求会有不同的处理方式
private void processFetchRequest(final ChunkFetchRequest req) {
ManagedBuffer buf;
try {
streamManager.checkAuthorization(reverseClient, req.streamChunkId.streamId);
buf = streamManager.getChunk(req.streamChunkId.streamId, req.streamChunkId.chunkIndex);
} catch (Exception e) {
logger.error(String.format("Error opening block %s for request from %s",
req.streamChunkId, getRemoteAddress(channel)), e);
respond(new ChunkFetchFailure(req.streamChunkId, Throwables.getStackTraceAsString(e)));
return;
}
streamManager.chunkBeingSent(req.streamChunkId.streamId);
respond(new ChunkFetchSuccess(req.streamChunkId, buf)).addListener(future -> {
streamManager.chunkSent(req.streamChunkId.streamId);
});
}
处理块获取请求
1.调用StreamManager的checkAuthorization方法，校验客户端是否有权限从给定的流中读取；
2.调用StreamManager的getChunk方法，获取单个的块（块被封装为ManagedBuffer）。由于单个的流只能与单个的TCP连接相关联，因此getChunk方法不能为了某个特殊的流而并行调用；
3.将ManagedBuffer和流的块Id封装为ChunkFetchSuccess后，调用respond方法返回给客户端。
private void processRpcRequest(final RpcRequest req) {
try {
rpcHandler.receive(reverseClient, req.body().nioByteBuffer(), new RpcResponseCallback() {
@Override
public void onSuccess(ByteBuffer response) {
respond(new RpcResponse(req.requestId, new NioManagedBuffer(response)));
}
@Override
public void onFailure(Throwable e) {
respond(new RpcFailure(req.requestId, Throwables.getStackTraceAsString(e)));
}
});
}
处理RPC请求,将RpcRequest消息的内容体、发送消息的客户端以及一个RpcResponseCallback类型的匿名内部类作为参数传递给了RpcHandler的receive方法。这就是说真正用于处理RpcRequest消息的是RpcHandler，而非TransportRequestHandler。由于RpcHandler是抽象类，其receive方法也是抽象方法，所以具体的 *** 作将由RpcHandler的实现了receive方法的子类来完成。所有继承RpcHandler的子类都需要在其receive方法的具体实现中回调RpcResponseCallback的onSuccess（处理成功时）或者onFailure（处理失败时）方法。从RpcResponseCallback的实现来看，无论处理结果成功还是失败，都将调用respond方法对客户端进行响应。
private void processStreamRequest(final StreamRequest req) {
ManagedBuffer buf;
try {
buf = streamManager.openStream(req.streamId);
} catch (Exception e) {
logger.error(String.format(
"Error opening stream %s for request from %s", req.streamId, getRemoteAddress(channel)), e);
respond(new StreamFailure(req.streamId, Throwables.getStackTraceAsString(e)));
return;
}
if (buf != null) {
streamManager.streamBeingSent(req.streamId);
respond(new StreamResponse(req.streamId, buf.size(), buf)).addListener(future -> {
streamManager.streamSent(req.streamId);
});
} else {
respond(new StreamFailure(req.streamId, String.format(
"Stream '%s' was not found.", req.streamId)));
}
}
处理流请求:
-
调用StreamManager的openStream方法将获取到的流数据封装为ManagedBuffer；
-
当成功或失败时调用respond方法向客户端响应。
private void processOneWayMessage(OneWayMessage req) { try { rpcHandler.receive(reverseClient, req.body().nioByteBuffer()); } catch (Exception e) { logger.error("Error while invoking RpcHandler#receive() for one-way message.", e); } finally { req.body().release(); } }
处理无需回复的RPC请求processOneWayMessage方法的实现processRpcRequest非常相似，区别在于processOneWayMessage调用了ONE_WAY_CALLBACK的receive方法，因而processOneWayMessage在处理完RPC请求后不会对客户端作出响应。
private ChannelFuture respond(Encodable result) {
SocketAddress remoteAddress = channel.remoteAddress();
return channel.writeAndFlush(result).addListener(future -> {
if (future.isSuccess()) {
logger.trace("Sent result {} to client {}", result, remoteAddress);
} else {
logger.error(String.format("Error sending result %s to %s; closing connection",
result, remoteAddress), future.cause());
channel.close();
}
});
}
最后使用netty调用了Channel的writeAndFlush方法来响应客户端。
欢迎分享，转载请注明来源：内存溢出
微信扫一扫
支付宝扫一扫
评论列表（0条）