gRPC服务端启动流程走查

瓜农老梁

发布于 2019-11-28 16:28:24

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发布于 2019-11-28 16:28:24

文章被收录于专栏：瓜农老梁

1、服务端启动示例

server = ServerBuilder.forPort(port) // @1
.addService(new GreeterImpl()) // @2
.build() // @3
.start(); // @4

小结： @1 构建监听地址SocketAddress @2 将service注册到缓存 @3 Server构建 @4 服务端启动

小结：服务端启动只有一行代码，设计简洁。

2、构建监听地址SocketAddress

2.1 SPI加载NettyServerProvider

代码坐标：io.grpc.ServerProvider

ServerBuilder.forPort(port)

public static ServerBuilder<?> forPort(int port) {
    return ServerProvider.provider().builderForPort(port);
}

private static final ServerProvider provider = ServiceProviders.load(
  ServerProvider.class,
  Collections.<Class<?>>emptyList(),
  ServerProvider.class.getClassLoader(),
  new PriorityAccessor<ServerProvider>() {
    @Override
    public boolean isAvailable(ServerProvider provider) {
      return provider.isAvailable();
    }

    @Override
    public int getPriority(ServerProvider provider) {
      return provider.priority();
    }
  }); // @1

@1 通过SPI对实例化NettyServerProvider String PREFIX = "META-INF/services/"; String fullName = PREFIX + service.getName(); c = Class.forName(cn, false, loader); 具体目录为：grpc-netty工程 META-INF/services/io.grpc.ServerProvider配置文件提供的配置io.grpc.netty.NettyServerProvider

2.2 根据指定端口创建监听地址

代码坐标1：io.grpc.netty.NettyServerProvider 代码坐标2：io.grpc.netty.NettyServerBuilder

protected NettyServerBuilder builderForPort(int port) {
   return NettyServerBuilder.forPort(port);
}

private final List<SocketAddress> listenAddresses = new ArrayList<>();

private NettyServerBuilder(int port) {
    this.listenAddresses.add(new InetSocketAddress(port)); // @1
}

@1 添加指定端口的SocketAddress监听地址并存入List容器缓存

小结：在服务端启动时指定监听端口，SPI加载NettyServerProvider，构建SocketAddress监听地址并存入List容器缓存。

3、将service注册到缓存

代码坐标：io.grpc.internal.AbstractServerImplBuilder

.addService(new GreeterImpl()) // @1

public final T addService(BindableService bindableService) {
    ...
    return addService(checkNotNull(bindableService, "bindableService").bindService()); // @2
  }
  
 Builder addService(ServerServiceDefinition service) {
  services.put(service.getServiceDescriptor().getName(), service); // @3
  return this;
 }

@1 GreeterImpl自定义提供的服务实现类需继承插件生产的抽象类GreeterGrpc.GreeterImplBase同时实现了BindableService接口 @2 bindService()不需要自己实现，插件自动生成代码时会自动生成其实现类 @3 将服务注册到缓存services中（LinkedHashMap）

小结：将自定义的服务提供实现类注册到缓存中。

4、Server构建

.build()
public final Server build() {
ServerImpl server = new ServerImpl(
    this,
    buildTransportServers(getTracerFactories()), // @1
    Context.ROOT);
for (InternalNotifyOnServerBuild notifyTarget : notifyOnBuildList) {
  notifyTarget.notifyOnBuild(server);
}
return server;
}

protected List<NettyServer> buildTransportServers(){
    ...
   for (SocketAddress listenAddress : listenAddresses) {
     NettyServer transportServer = new NettyServer(...) // @2
   }
}

@1 创建NettyServer @2 为注册的每个SocketAddress创建NettyServer

4.1 NettyServer构造函数参数

NettyServer(
  SocketAddress address, ChannelFactory<? extends ServerChannel> channelFactory, // @1
  Map<ChannelOption<?>, ?> channelOptions, // @2 
  ObjectPool<? extends EventLoopGroup/**一组EventLoop**/> bossGroupPool, // @3
  ObjectPool<? extends EventLoopGroup> workerGroupPool, // @4 
  ProtocolNegotiator protocolNegotiator, // @5
  List<? extends ServerStreamTracer.Factory> streamTracerFactories, // @6
  TransportTracer.Factory transportTracerFactory, // @7
  int maxStreamsPerConnection, // @8
  int flowControlWindow, // @9
  int maxMessageSize, // @10
  int maxHeaderListSize, // @11
  long keepAliveTimeInNanos, // @12
  long keepAliveTimeoutInNanos, // @13
  long maxConnectionIdleInNanos, // @14
  long maxConnectionAgeInNanos, // @15
  long maxConnectionAgeGraceInNanos,// @16
  boolean permitKeepAliveWithoutCalls, // @17
  long permitKeepAliveTimeInNanos, // @18
  InternalChannelz channelz
)

@1 Channel工厂类创建新的通道 @2 ChannelOption设置项 @3 用于accept客户端链接的线程池转发给workerGroupPool @4 初始化客户端连接的线程池 @5 遵循HTTP/2规范的通信协商 @6 用于创建ServerStreamTracer @7 创建TransportTracer工厂类用于统计通信流量 @8 每个连接允许的最大Streams @9 HTTP/2流控窗口大小 @10 服务端允许的最大消息体大小该属性已废弃使用maxInboundMessageSize代替 @11 接受最大Header大小已废弃使用maxInboundMetadataSize代替 @12 存活时间单位纳秒在存活时间内发送下一次keepAlive ping @13 keepalive ping requests的超时时间 @14 连接最大空闲时间超过后将优雅关闭 @15 连接最大存活时间超过后将优雅关闭 @16 当达到最大连接时RPCs有优雅关闭时间，在优雅时间内RPC请求未完成将被取消 @17 是否允许在没有RPC调用的情况下客户端发送keep-alive HTTP/2 PINGs 默认false @18 允许客户端保持连接的最大时间默认5分钟

5、服务端启动

代码坐标：ServerImpl.start

.start()

public ServerImpl start() throws IOException {
synchronized (lock) {
  checkState(!started, "Already started");// @1
  checkState(!shutdown, "Shutting down");// @2
  ServerListenerImpl listener = new ServerListenerImpl(); // @3
  for (InternalServer ts : transportServers) {
    ts.start(listener); // @4
    activeTransportServers++; // @5
  }
  executor = Preconditions.checkNotNull(executorPool.getObject(), "executor"); // @6
  started = true; // @7
  return this;
}

@1 检查服务是否启动 @2 检查服务是否正在关闭 @3 transport创建监听器 @4 server启动 @5 活动server统计 @6 从守护线程池中获取一个线程 @7 服务启动标记

代码坐标：NettyServer.start

public void start(ServerListener serverListener) {
    ServerBootstrap b = new ServerBootstrap();
    ...
     b.childHandler(new ChannelInitializer<Channel>() {
      @Override
      public void initChannel(Channel ch) {
        NettyServerTransport transport =
            new NettyServerTransport(...); // @1
      }
      transport.start(transportListener);
      ...
    });
}

代码坐标：NettyServerTransport.start

...
grpcHandler = createHandler(listener, channelUnused); // @2 
...

代码坐标：NettyServerHandler.newHandler

 static NettyServerHandler newHandler(...){ // @3
    final Http2Connection connection = new DefaultHttp2Connection(true);
    WeightedFairQueueByteDistributor dist = new WeightedFairQueueByteDistributor(connection);
    dist.allocationQuantum(16 * 1024); // Make benchmarks fast again.
    DefaultHttp2RemoteFlowController controller =
        new DefaultHttp2RemoteFlowController(connection, dist);
    connection.remote().flowController(controller);
    final KeepAliveEnforcer keepAliveEnforcer = new KeepAliveEnforcer(
        permitKeepAliveWithoutCalls, permitKeepAliveTimeInNanos, TimeUnit.NANOSECONDS);

    // Create the local flow controller configured to auto-refill the connection window.
    connection.local().flowController(
        new DefaultHttp2LocalFlowController(connection, DEFAULT_WINDOW_UPDATE_RATIO, true));
    frameWriter = new WriteMonitoringFrameWriter(frameWriter, keepAliveEnforcer);
    Http2ConnectionEncoder encoder = new DefaultHttp2ConnectionEncoder(connection, frameWriter);
    encoder = new Http2ControlFrameLimitEncoder(encoder, 10000);
    Http2ConnectionDecoder decoder = new DefaultHttp2ConnectionDecoder(connection, encoder,
        frameReader);

    Http2Settings settings = new Http2Settings();
    settings.initialWindowSize(flowControlWindow);
    settings.maxConcurrentStreams(maxStreams);
    settings.maxHeaderListSize(maxHeaderListSize);

    return new NettyServerHandler(...)
 }

@1 创建NettyServerTransport @2 基于Netty HTTP/2构建gRPC服务端 @3 具体的Netty HTTP/2实现，具体在分析HTTP/2时再回头分析