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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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package org.apache.flink.runtime.registration;

import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.runtime.rpc.RpcGateway;

import org.slf4j.Logger;

import java.io.Serializable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

import static org.apache.flink.util.Preconditions.checkNotNull;
import static org.apache.flink.util.Preconditions.checkState;

/**
 * This utility class implements the basis of RPC connecting from one component to another component,
 * for example the RPC connection from TaskExecutor to ResourceManager.
 * This {@code RegisteredRpcConnection} implements registration and get target gateway.
 *
 * 

The registration gives access to a future that is completed upon successful registration. * The RPC connection can be closed, for example when the target where it tries to register * at looses leader status. * * @param The type of the fencing token * @param The type of the gateway to connect to. * @param The type of the successful registration responses. */ public abstract class RegisteredRpcConnection { private static final AtomicReferenceFieldUpdater REGISTRATION_UPDATER = AtomicReferenceFieldUpdater.newUpdater( RegisteredRpcConnection.class, RetryingRegistration.class, "pendingRegistration"); /** The logger for all log messages of this class. */ protected final Logger log; /** The fencing token fo the remote component. */ private final F fencingToken; /** The target component Address, for example the ResourceManager Address. */ private final String targetAddress; /** Execution context to be used to execute the on complete action of the ResourceManagerRegistration. */ private final Executor executor; /** The Registration of this RPC connection. */ private volatile RetryingRegistration pendingRegistration; /** The gateway to register, it's null until the registration is completed. */ private volatile G targetGateway; /** Flag indicating that the RPC connection is closed. */ private volatile boolean closed; // ------------------------------------------------------------------------ public RegisteredRpcConnection(Logger log, String targetAddress, F fencingToken, Executor executor) { this.log = checkNotNull(log); this.targetAddress = checkNotNull(targetAddress); this.fencingToken = checkNotNull(fencingToken); this.executor = checkNotNull(executor); } // ------------------------------------------------------------------------ // Life cycle // ------------------------------------------------------------------------ @SuppressWarnings("unchecked") public void start() { checkState(!closed, "The RPC connection is already closed"); checkState(!isConnected() && pendingRegistration == null, "The RPC connection is already started"); final RetryingRegistration newRegistration = createNewRegistration(); if (REGISTRATION_UPDATER.compareAndSet(this, null, newRegistration)) { newRegistration.startRegistration(); } else { // concurrent start operation newRegistration.cancel(); } } public boolean tryReconnect() { checkState(isConnected(), "Cannot reconnect to an unknown destination."); if (closed) { return false; } else { final RetryingRegistration currentPendingRegistration = pendingRegistration; if (currentPendingRegistration != null) { currentPendingRegistration.cancel(); } final RetryingRegistration newRegistration = createNewRegistration(); if (REGISTRATION_UPDATER.compareAndSet(this, currentPendingRegistration, newRegistration)) { newRegistration.startRegistration(); } else { // concurrent modification newRegistration.cancel(); return false; } // double check for concurrent close operations if (closed) { newRegistration.cancel(); return false; } else { return true; } } } /** * This method generate a specific Registration, for example TaskExecutor Registration at the ResourceManager. */ protected abstract RetryingRegistration generateRegistration(); /** * This method handle the Registration Response. */ protected abstract void onRegistrationSuccess(S success); /** * This method handle the Registration failure. */ protected abstract void onRegistrationFailure(Throwable failure); /** * Close connection. */ public void close() { closed = true; // make sure we do not keep re-trying forever if (pendingRegistration != null) { pendingRegistration.cancel(); } } public boolean isClosed() { return closed; } // ------------------------------------------------------------------------ // Properties // ------------------------------------------------------------------------ public F getTargetLeaderId() { return fencingToken; } public String getTargetAddress() { return targetAddress; } /** * Gets the RegisteredGateway. This returns null until the registration is completed. */ public G getTargetGateway() { return targetGateway; } public boolean isConnected() { return targetGateway != null; } // ------------------------------------------------------------------------ @Override public String toString() { String connectionInfo = "(ADDRESS: " + targetAddress + " FENCINGTOKEN: " + fencingToken + ")"; if (isConnected()) { connectionInfo = "RPC connection to " + targetGateway.getClass().getSimpleName() + " " + connectionInfo; } else { connectionInfo = "RPC connection to " + connectionInfo; } if (isClosed()) { connectionInfo += " is closed"; } else if (isConnected()){ connectionInfo += " is established"; } else { connectionInfo += " is connecting"; } return connectionInfo; } // ------------------------------------------------------------------------ // Internal methods // ------------------------------------------------------------------------ private RetryingRegistration createNewRegistration() { RetryingRegistration newRegistration = checkNotNull(generateRegistration()); CompletableFuture> future = newRegistration.getFuture(); future.whenCompleteAsync( (Tuple2 result, Throwable failure) -> { if (failure != null) { if (failure instanceof CancellationException) { // we ignore cancellation exceptions because they originate from cancelling // the RetryingRegistration log.debug("Retrying registration towards {} was cancelled.", targetAddress); } else { // this future should only ever fail if there is a bug, not if the registration is declined onRegistrationFailure(failure); } } else { targetGateway = result.f0; onRegistrationSuccess(result.f1); } }, executor); return newRegistration; } }





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