A proposed fix for GRADLE-2495

TcpOutgoingConnector.java

/*
 * Copyright 2010 the original author or authors.
 *
 * Licensed 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
 * limitations under the License.
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package org.gradle.messaging.remote.internal.inet;

import org.gradle.messaging.remote.Address;
import org.gradle.messaging.remote.internal.ConnectException;
import org.gradle.messaging.remote.internal.Connection;
import org.gradle.messaging.remote.internal.MessageSerializer;
import org.gradle.messaging.remote.internal.OutgoingConnector;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.nio.channels.ClosedByInterruptException;
import java.nio.channels.SocketChannel;
import java.util.List;
import java.util.concurrent.CancellationException;

public class TcpOutgoingConnector<T> implements OutgoingConnector<T> {
    private static final Logger LOGGER = LoggerFactory.getLogger(TcpOutgoingConnector.class);
    private final MessageSerializer<T> serializer;

    public TcpOutgoingConnector(MessageSerializer<T> serializer) {
        this.serializer = serializer;
    }

    public Connection<T> connect(Address destinationAddress) {
        if (!(destinationAddress instanceof InetEndpoint)) {
            throw new IllegalArgumentException(String.format("Cannot create a connection to address of unknown type: %s.", destinationAddress));
        }
        InetEndpoint address = (InetEndpoint) destinationAddress;
        LOGGER.debug("Attempting to connect to {}.", address);

        // Try each address in turn. Not all of them are necessarily reachable (eg when socket option IPV6_V6ONLY
        // is on - the default for debian and others), so we will try each of them until we can connect
        List<InetAddress> candidateAddresses = address.getCandidates();

        // Now try each address
        Exception failure = null;
        for (InetAddress candidate : candidateAddresses) {
            LOGGER.debug("Trying to connect to address {}.", candidate);
            SocketChannel socketChannel;
            try {
                socketChannel = SocketChannel.open(new InetSocketAddress(candidate, address.getPort()));
            } catch (ClosedByInterruptException ex) {
                throw new CancellationException();
            } catch (Exception e) {
                LOGGER.debug("Cannot connect to address {}, skipping.", candidate);
                if (failure == null) {
                    failure = e;
                }
                else {
                    // In Java7 add "e" as a suppressed exception to "failure".
                    LOGGER.debug("Suppressing exception.", e);
                }
                continue;
            }
            LOGGER.debug("Connected to address {}.", candidate);
            return new SocketConnection<T>(socketChannel, serializer);
        }

        throw new ConnectException(String.format("Could not connect to server %s. Tried addresses: %s.",
                destinationAddress, candidateAddresses), failure);
    }
}