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This project contains some of the configurable modules used within the Heritrix application to crawl the web. The modules in this project can be used in applications other than Heritrix, however.
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/*
 *  This file is part of the Heritrix web crawler (crawler.archive.org).
 *
 *  Licensed to the Internet Archive (IA) by one or more individual 
 *  contributors. 
 *
 *  The IA 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
 *  limitations under the License.
 */

package org.archive.modules.fetcher;

import java.io.Closeable;
import java.io.Serializable;
import java.util.Set;
import java.util.logging.Logger;

import org.apache.commons.collections.Closure;
import org.archive.modules.net.CrawlHost;
import org.archive.modules.net.CrawlServer;
import org.archive.modules.net.ServerCache;
import org.archive.util.ObjectIdentityCache;
import org.archive.util.ObjectIdentityMemCache;
import org.archive.util.Supplier;


/**
 * Server and Host cache.
 * @author stack
 * @version $Date$, $Revision$
 */
public class DefaultServerCache extends ServerCache implements Closeable, Serializable {
    private static final long serialVersionUID = 1L;

    @SuppressWarnings("unused")
    private static Logger logger =
        Logger.getLogger(DefaultServerCache.class.getName());
    
    
    /**
     * hostname[:port] -> CrawlServer.
     * Set in the initialization.
     */
    protected ObjectIdentityCache servers = null;
    
    /**
     * hostname -> CrawlHost.
     * Set in the initialization.
     */
    protected ObjectIdentityCache hosts = null;
    
    /**
     * Constructor.
     */
    public DefaultServerCache() {
        this(
            new ObjectIdentityMemCache(), 
            new ObjectIdentityMemCache());
    }
    
    
    
    public DefaultServerCache(ObjectIdentityCache servers, 
            ObjectIdentityCache hosts) {
        this.servers = servers;
        this.hosts = hosts;
    }
    
    /**
     * Get the {@link CrawlServer} associated with name.
     * @param serverKey Server name we're to return server for.
     * @return CrawlServer instance that matches the passed server name.
     */
    public CrawlServer getServerFor(final String serverKey) {
        CrawlServer cserver = servers.getOrUse(
                serverKey,
                new Supplier() {
                    public CrawlServer get() {
                        String skey = new String(serverKey); // ensure private minimal key
                        return new CrawlServer(skey);
                    }});
        return cserver;
    }
    
    /**
     * Get the {@link CrawlHost} associated with name.
     * @param hostname Host name we're to return Host for.
     * @return CrawlHost instance that matches the passed Host name.
     */
    public CrawlHost getHostFor(final String hostname) {
        if (hostname == null || hostname.length() == 0) {
            return null;
        }
        CrawlHost host = hosts.getOrUse(
                hostname,
                new Supplier() {
                    public CrawlHost get() {
                        String hkey = new String(hostname); // ensure private minimal key
                        return new CrawlHost(hkey);
                    }});
        if (host != null && host.getIP() != null
                && "0.0.0.0".equals(host.getIP().getHostAddress())) {
            throw new IllegalStateException("got suspicious value 0.0.0.0 for " + hostname);
        }
        return host;
    }

    /**
     * @param serverKey Key to use doing lookup.
     * @return True if a server instance exists.
     */
    public boolean containsServer(String serverKey) {
        return (CrawlServer) servers.get(serverKey) != null; 
    }

    /**
     * @param hostKey Key to use doing lookup.
     * @return True if a host instance exists.
     */
    public boolean containsHost(String hostKey) {
        return (CrawlHost) hosts.get(hostKey) != null; 
    }

    /**
     * Called when shutting down the cache so we can do clean up.
     */
    public void close() {
        if (this.hosts != null) {
            // If we're using a bdb bigmap, the call to clear will
            // close down the bdb database.
            this.hosts.close();
            this.hosts = null;
        }
        if (this.servers != null) { 
            this.servers.close();
            this.servers = null;
        }
    }

    /**
     * NOTE: Should not mutate the CrawlHost instance so retrieved; depending on
     * the hostscache implementation, the change may not be reliably persistent.  
     * 
     * @see org.archive.modules.net.ServerCache#forAllHostsDo(org.apache.commons.collections.Closure)
     */
    public void forAllHostsDo(Closure c) {
        for(String host : hosts.keySet()) {
            c.execute(hosts.get(host));
        }
    }
    
    public Set hostKeys() {
        return hosts.keySet();
    }
}