Flink的rpc组件有哪些
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Flink采用akka来实现rpc服务。其中有这几个重要组件:RpcServer、RpcService、AkkaRpcActor、RpcEndpoint。
这几个组件作用如下:
(1)RpcEndpoint
提供具体rpc服务。主要实现有 ResourceManager 和 TaskExecutor,
①YarnResourceManager为AM容器中启动的服务,持有ResourceManager和NodeManager的客户端
②TaskExecutor为NM容器中启动taskmanager的类
(2)AkkaRpcService
提供rpc的服务类。该类内部持有ActorSystem实例和Supervisor实例。Supervisor中含有SupervisorActor实例,SupervisorActor用于创建其他Actor,可以理解为根Actor。RpcEndpoint在构造时,通过AkkaRpcService的startServer()方法,获取RpcServer实例。
publicRpcServer startServer(C rpcEndpoint) { checkNotNull(rpcEndpoint, "rpc endpoint"); final SupervisorActor.ActorRegistration actorRegistration = registerAkkaRpcActor(rpcEndpoint); final ActorRef actorRef = actorRegistration.getActorRef(); final CompletableFuture actorTerminationFuture = actorRegistration.getTerminationFuture(); LOG.info("Starting RPC endpoint for {} at {} .", rpcEndpoint.getClass().getName(), actorRef.path()); final String akkaAddress = AkkaUtils.getAkkaURL(actorSystem, actorRef); final String hostname; Option host = actorRef.path().address().host(); if (host.isEmpty()) { hostname = "localhost"; } else { hostname = host.get(); } Set > implementedRpcGateways = new HashSet<>(RpcUtils.extractImplementedRpcGateways(rpcEndpoint.getClass())); implementedRpcGateways.add(RpcServer.class); implementedRpcGateways.add(AkkaBasedEndpoint.class); final InvocationHandler akkaInvocationHandler; if (rpcEndpoint instanceof FencedRpcEndpoint) { // a FencedRpcEndpoint needs a FencedAkkaInvocationHandler akkaInvocationHandler = new FencedAkkaInvocationHandler<>( akkaAddress, hostname, actorRef, configuration.getTimeout(), configuration.getMaximumFramesize(), actorTerminationFuture, ((FencedRpcEndpoint>) rpcEndpoint)::getFencingToken, captureAskCallstacks); implementedRpcGateways.add(FencedMainThreadExecutable.class); } else { akkaInvocationHandler = new AkkaInvocationHandler( akkaAddress, hostname, actorRef, configuration.getTimeout(), configuration.getMaximumFramesize(), actorTerminationFuture, captureAskCallstacks); } // Rather than using the System ClassLoader directly, we derive the ClassLoader // from this class . That works better in cases where Flink runs embedded and all Flink // code is loaded dynamically (for example from an OSGI bundle) through a custom ClassLoader ClassLoader classLoader = getClass().getClassLoader(); @SuppressWarnings("unchecked") RpcServer server = (RpcServer) Proxy.newProxyInstance( classLoader, implementedRpcGateways.toArray(new Class>[implementedRpcGateways.size()]), akkaInvocationHandler); return server; }
先创建RpcEndpoint对应的ActorRef,然后创建RpcServer的代理类AkkaInvocationHandler或FencedAkkaInvocationHandler,并将ActorRef实例赋给其成员属性 rpcEndpoint:ActorRef。这里的ActorRef即为AkkaRpcActor或FencedAkkaRpcActor实例
(3)RpcServer
用来启动rpc服务,通常不直接调用,而是调用其动态代理类AkkaInvocationHandler或FencedAkkaInvocationHandler的start()方法
(4)AkkaInvocationHandler或FencedAkkaInvocationHandler
RpcServer的动态代理类。start()方法用来启动服务:
public void start() { rpcEndpoint.tell(ControlMessages.START, ActorRef.noSender()); }
这里向rpcEndpoint,即AkkaRpcActor或FencedAkkaRpcActor实例发送一条ControlMessages.START消息
(5)AkkaRpcActor
响应rpc消息的actor。其createReceive():
public Receive createReceive() { return ReceiveBuilder.create() .match(RemoteHandshakeMessage.class, this::handleHandshakeMessage) .match(ControlMessages.class, this::handleControlMessage) .matchAny(this::handleMessage) .build(); }
当消息为ControlMessages.START,调用StoppedState 的start()方法
public State start(AkkaRpcActor> akkaRpcActor) { akkaRpcActor.mainThreadValidator.enterMainThread(); try { akkaRpcActor.rpcEndpoint.internalCallOnStart(); } catch (Throwable throwable) { akkaRpcActor.stop( RpcEndpointTerminationResult.failure( new AkkaRpcException( String.format("Could not start RpcEndpoint %s.", akkaRpcActor.rpcEndpoint.getEndpointId()), throwable))); } finally { akkaRpcActor.mainThreadValidator.exitMainThread(); } return StartedState.STARTED; }
在start()方法中调用具体提供服务的RpcEndpoint实现类internalCallOnStart()方法来启动服务。internalCallOnStart()方法中会调用onStart()方法。
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