yacy_search_server/source/de/anomic/plasma/plasmaCrawlBalancer.java

// plasmaCrawlBalancer.java 
// -----------------------
// part of YaCy
// (C) by Michael Peter Christen; mc@anomic.de
// first published on http://www.anomic.de
// Frankfurt, Germany, 2005
// created: 24.09.2005
//
// 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 2 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, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// Using this software in any meaning (reading, learning, copying, compiling,
// running) means that you agree that the Author(s) is (are) not responsible
// for cost, loss of data or any harm that may be caused directly or indirectly
// by usage of this softare or this documentation. The usage of this software
// is on your own risk. The installation and usage (starting/running) of this
// software may allow other people or application to access your computer and
// any attached devices and is highly dependent on the configuration of the
// software which must be done by the user of the software; the author(s) is
// (are) also not responsible for proper configuration and usage of the
// software, even if provoked by documentation provided together with
// the software.
//
// Any changes to this file according to the GPL as documented in the file
// gpl.txt aside this file in the shipment you received can be done to the
// lines that follows this copyright notice here, but changes must not be
// done inside the copyright notive above. A re-distribution must contain
// the intact and unchanged copyright notice.
// Contributions and changes to the program code must be marked as such.

package de.anomic.plasma;

import java.io.File;
import java.io.IOException;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import java.util.ArrayList;

import de.anomic.kelondro.kelondroRecords;
import de.anomic.kelondro.kelondroStack;

public class plasmaCrawlBalancer {

    private kelondroStack stack;
    private HashMap domainStacks;
    
    public plasmaCrawlBalancer(File stackFile, long buffersize) throws IOException {
        if (stackFile.exists())
            stack = new kelondroStack(stackFile, buffersize);
        else
            stack = new kelondroStack(stackFile, buffersize, new int[] {plasmaURL.urlHashLength});
        domainStacks = new HashMap();
    }

    public void close() {
        try { flushAll(); } catch (IOException e) {}
        try { stack.close(); } catch (IOException e) {}
        stack = null;
    }
    
    public void reset() throws IOException {
        stack = kelondroStack.reset(stack);
        domainStacks = new HashMap();
    }
    
    public Iterator iterator() {
        // iterates byte[] - objects
        return new KeyIterator(stack.iterator());
    }
    
    public int size() {
        return stack.size() + sizeDomainStacks();
    }
    
    private int sizeDomainStacks() {
        int sum = 0;
        Iterator i = domainStacks.values().iterator();
        while (i.hasNext()) sum += ((ArrayList) i.next()).size();
        return sum;
    }
    
    private void flushOnce() throws IOException {
        // takes one entry from every domain stack and puts it on the file stack
        synchronized (domainStacks) {
            Iterator i = domainStacks.entrySet().iterator();
            Map.Entry entry;
            ArrayList list;
            while (i.hasNext()) {
                entry = (Map.Entry) i.next();
                list = (ArrayList) entry.getValue();
                stack.push(new byte[][]{(byte[]) list.remove(0)});
                if (list.size() == 0) i.remove();
            }
        }
    }
    
    private void flushAll() throws IOException {
        while (domainStacks.size() > 0) flushOnce();
    }
    
    public synchronized void add(String domain, byte[] hash) throws IOException {
        //stack.push(new byte[][]{hash});
        ArrayList domainList = (ArrayList) domainStacks.get(domain);
        if (domainList == null) {
            // create new list
            domainList = new ArrayList();
            domainList.add(hash);
            domainStacks.put(domain, domainList);
        } else {
            // extend existent domain list
            domainList.add(hash);
        }
        
        // check size of domainStacks and flush
        if ((domainStacks.size() > 20) || (sizeDomainStacks() > 400)) {
            flushOnce();
        }
    }
    
    public synchronized Object[] /*String, byte[]*/ get() throws IOException {
        // returns a pair of domain/hash from the stack
        // if the domain is unknown, a null/hash is returned
        if (stack.size() > 0) {
            return new Object[]{null, stack.pop()[0]};
        } else if (domainStacks.size() > 0) {
            flushOnce();
            return new Object[]{null, stack.pop()[0]};
        } else {
            return null;
        }
    }
    
    public synchronized byte[] top(int dist) throws IOException {
        flushAll();
        return stack.top(dist)[0];
    }
    
    public void clear() throws IOException {
        domainStacks.clear();
        stack.clear();
    }
    
    public class KeyIterator implements Iterator {

        Iterator ni;
        
        public KeyIterator(Iterator i) {
            ni = i;
        }
        
        public boolean hasNext() {
            return ni.hasNext();
        }
        
        public Object next() {
            return ((kelondroRecords.Node) ni.next()).getKey();
        }
        
        public void remove() {
        }
        
    }
    
}