org.commoncrawl.service.directory.BlockingClient.java Source code

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Here is the source code for org.commoncrawl.service.directory.BlockingClient.java

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/**
 * Copyright 2008 - CommonCrawl Foundation
 * 
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation, either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 **/

package org.commoncrawl.service.directory;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.nio.charset.Charset;
import java.util.concurrent.Semaphore;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.record.Buffer;
import org.commoncrawl.async.EventLoop;
import org.commoncrawl.crawl.common.internal.CrawlEnvironment;
import org.commoncrawl.rpc.base.internal.AsyncClientChannel;
import org.commoncrawl.rpc.base.internal.AsyncRequest;

/**
 * 
 * @author rana
 *
 */
public class BlockingClient implements AsyncClientChannel.ConnectionCallback {

    EventLoop _eventLoop = null;
    AsyncClientChannel _channel;
    DirectoryService.AsyncStub _serviceStub;
    Semaphore _blockingCallSemaphore = null;
    Buffer _buffer = new Buffer();

    private static final Log LOG = LogFactory.getLog(BlockingClient.class);

    BlockingClient() {
        _eventLoop = new EventLoop();
        _eventLoop.start();
    }

    public static BufferedReader createReaderFromPath(InetAddress directoryServiceServer, String itemPath)
            throws IOException {
        // load primary path via directory service client
        return new BufferedReader(new InputStreamReader(
                new ByteArrayInputStream(BlockingClient.loadDataFromPath(directoryServiceServer, itemPath)),
                Charset.forName("UTF8")));
    }

    public static byte[] loadDataFromPath(InetAddress directoryServiceServer, String itemPath) throws IOException {

        final BlockingClient client = new BlockingClient();

        try {

            client.connect(directoryServiceServer);

            DirectoryServiceQuery query = new DirectoryServiceQuery();
            query.setItemPath(itemPath);

            client._blockingCallSemaphore = new Semaphore(0);
            client._serviceStub.query(query,
                    new AsyncRequest.Callback<DirectoryServiceQuery, DirectoryServiceItemList>() {
                        @Override
                        public void requestComplete(
                                AsyncRequest<DirectoryServiceQuery, DirectoryServiceItemList> request) {

                            if (request.getStatus() == AsyncRequest.Status.Success) {

                                DirectoryServiceItem item = request.getOutput().getItems().get(0);
                                client._buffer = new Buffer(item.getItemData().getReadOnlyBytes());
                            } else {
                                LOG.error("Request:" + request.getInput().getItemPath() + " returned NULL result.");
                            }
                            if (client._blockingCallSemaphore != null) {
                                client._blockingCallSemaphore.release();
                            }
                        }
                    });
            client._blockingCallSemaphore.acquireUninterruptibly();
            client._blockingCallSemaphore = null;

            if (client._buffer.getCount() == 0) {
                throw new IOException("Failed to retrieve item at path:" + itemPath);
            } else {
                return client._buffer.get();
            }

        } catch (IOException e) {
            throw e;
        }
    }

    void shutdown() {
        if (_channel != null) {
            try {
                _channel.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            _channel = null;
            _eventLoop.stop();
        }
    }

    void connect(InetAddress address) throws IOException {
        try {
            System.out.println("Connecting to server at:" + address);
            _channel = new AsyncClientChannel(_eventLoop, null,
                    new InetSocketAddress(address, CrawlEnvironment.DIRECTORY_SERVICE_RPC_PORT), this);
            _blockingCallSemaphore = new Semaphore(0);
            _channel.open();
            _serviceStub = new DirectoryService.AsyncStub(_channel);
            System.out.println("Waiting on Connect... ");
            _blockingCallSemaphore.acquireUninterruptibly();
            System.out.println("Connect Semaphore Released... ");
            _blockingCallSemaphore = null;

            if (!_channel.isOpen()) {
                throw new IOException("Connection Failed!");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void OutgoingChannelConnected(AsyncClientChannel channel) {
        System.out.println("OutgoingChannelConnected... ");
        if (_blockingCallSemaphore != null) {
            _blockingCallSemaphore.release();
        }
    }

    @Override
    public boolean OutgoingChannelDisconnected(AsyncClientChannel channel) {
        System.out.println("OutgoingChannelDisconnected... ");
        if (_blockingCallSemaphore != null) {
            _blockingCallSemaphore.release();
        }
        return true;
    }

}