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Redis Java client with features of In-Memory Data Grid
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/**
 * Copyright 2016 Nikita Koksharov
 *
 * 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.
 */
package org.redisson.client.handler;

import java.net.SocketAddress;
import java.util.Map.Entry;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;

import org.redisson.client.RedisConnection;
import org.redisson.client.RedisPubSubConnection;
import org.redisson.client.codec.Codec;
import org.redisson.client.protocol.CommandData;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.group.ChannelGroup;
import io.netty.util.Timeout;
import io.netty.util.Timer;
import io.netty.util.TimerTask;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.FutureListener;

/**
 * 
 * @author Nikita Koksharov
 *
 */
@Sharable
public class ConnectionWatchdog extends ChannelInboundHandlerAdapter {

    private final Logger log = LoggerFactory.getLogger(getClass());

    private final Timer timer;
    private final Bootstrap bootstrap;
    private final ChannelGroup channels;
    private static final int BACKOFF_CAP = 12;

    public ConnectionWatchdog(Bootstrap bootstrap, ChannelGroup channels, Timer timer) {
        this.bootstrap = bootstrap;
        this.channels  = channels;
        this.timer = timer;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        channels.add(ctx.channel());
        ctx.fireChannelActive();
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        RedisConnection connection = RedisConnection.getFrom(ctx.channel());
        if (connection != null) {
            connection.fireDisconnected();
            if (!connection.isClosed()) {
                if (connection.isFastReconnect()) {
                    tryReconnect(connection, 1);
                } else {
                    reconnect(connection, 1);
                }
            }
        }
        ctx.fireChannelInactive();
    }
    
    private void reconnect(final RedisConnection connection, final int attempts){
        int timeout = 2 << attempts;
        if (bootstrap.config().group().isShuttingDown()) {
            return;
        }
        
        try {
            timer.newTimeout(new TimerTask() {
                @Override
                public void run(Timeout timeout) throws Exception {
                    tryReconnect(connection, Math.min(BACKOFF_CAP, attempts + 1));
                }
            }, timeout, TimeUnit.MILLISECONDS);
        } catch (IllegalStateException e) {
            // skip
        }
    }

    private void tryReconnect(final RedisConnection connection, final int nextAttempt) {
        if (connection.isClosed() || bootstrap.config().group().isShuttingDown()) {
            return;
        }

        log.debug("reconnecting {} to {} ", connection, connection.getRedisClient().getAddr(), connection);

        try {
            bootstrap.connect(connection.getRedisClient().getAddr()).addListener(new ChannelFutureListener() {

                @Override
                public void operationComplete(final ChannelFuture future) throws Exception {
                    if (connection.isClosed() || bootstrap.config().group().isShuttingDown()) {
                        return;
                    }

                    if (future.isSuccess()) {
                        final Channel channel = future.channel();

                        RedisConnection c = RedisConnection.getFrom(channel);
                        c.getConnectionPromise().addListener(new FutureListener() {
                            @Override
                            public void operationComplete(Future future) throws Exception {
                                if (future.isSuccess()) {
                                    refresh(connection, channel);
                                    log.debug("{} connected to {}, command: {}", connection, connection.getRedisClient().getAddr(), connection.getCurrentCommand());
                                } else {
                                    log.warn("Can't connect " + connection + " to " + connection.getRedisClient().getAddr(), future.cause());
                                }
                                
                            }
                        });
                        return;
                    }

                    reconnect(connection, nextAttempt);
                }
            });
        } catch (RejectedExecutionException e) {
            // skip
        }
    }

    private void reattachPubSub(RedisConnection connection) {
        if (connection instanceof RedisPubSubConnection) {
            RedisPubSubConnection conn = (RedisPubSubConnection) connection;
            for (Entry entry : conn.getChannels().entrySet()) {
                conn.subscribe(entry.getValue(), entry.getKey());
            }
            for (Entry entry : conn.getPatternChannels().entrySet()) {
                conn.psubscribe(entry.getValue(), entry.getKey());
            }
        }
    }

    private void refresh(RedisConnection connection, Channel channel) {
        CommandData currentCommand = connection.getCurrentCommand();
        connection.fireConnected();
        connection.updateChannel(channel);
        
        if (connection.isFastReconnect()) {
            connection.clearFastReconnect();
        }

        reattachBlockingQueue(connection, currentCommand);            
        reattachPubSub(connection);
    }

    private void reattachBlockingQueue(RedisConnection connection, CommandData currentCommand) {
        if (currentCommand == null 
                || !currentCommand.isBlockingCommand()
                    || currentCommand.getPromise().isDone()) {
            return;
        }

        log.debug("blocking queue sent " + connection);
        ChannelFuture future = connection.send(currentCommand);
        final CommandData cd = currentCommand;
        future.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                if (!future.isSuccess()) {
                    log.error("Can't reconnect blocking queue to new connection. {}", cd);
                }
            }
        });
    }

}