/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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.
*/
using System;
namespace Lucene.Net.Search
{
/// Filter caching singleton. It can be used
/// to save filters locally for reuse.
/// This class makes it possble to cache Filters even when using RMI, as it
/// keeps the cache on the seaercher side of the RMI connection.
///
/// Also could be used as a persistent storage for any filter as long as the
/// filter provides a proper hashCode(), as that is used as the key in the cache.
///
/// The cache is periodically cleaned up from a separate thread to ensure the
/// cache doesn't exceed the maximum size.
///
public class FilterManager
{
protected internal static FilterManager manager;
/// The default maximum number of Filters in the cache
protected internal const int DEFAULT_CACHE_CLEAN_SIZE = 100;
/// The default frequency of cache clenup
protected internal const long DEFAULT_CACHE_SLEEP_TIME = 1000 * 60 * 10;
/// The cache itself
protected internal System.Collections.IDictionary cache;
/// Maximum allowed cache size
protected internal int cacheCleanSize;
/// Cache cleaning frequency
protected internal long cleanSleepTime;
/// Cache cleaner that runs in a separate thread
protected internal FilterCleaner filterCleaner;
public static FilterManager GetInstance()
{
lock (typeof(Lucene.Net.Search.FilterManager))
{
if (manager == null)
{
manager = new FilterManager();
}
return manager;
}
}
/// Sets up the FilterManager singleton.
protected internal FilterManager()
{
cache = new System.Collections.Hashtable();
cacheCleanSize = DEFAULT_CACHE_CLEAN_SIZE; // Let the cache get to 100 items
cleanSleepTime = DEFAULT_CACHE_SLEEP_TIME; // 10 minutes between cleanings
filterCleaner = new FilterCleaner(this);
SupportClass.ThreadClass fcThread = new SupportClass.ThreadClass(new System.Threading.ThreadStart(filterCleaner.Run));
// setto be a Daemon so it doesn't have to be stopped
fcThread.IsBackground = true;
fcThread.Start();
}
/// Sets the max size that cache should reach before it is cleaned up
/// maximum allowed cache size
///
public virtual void SetCacheSize(int cacheCleanSize)
{
this.cacheCleanSize = cacheCleanSize;
}
/// Sets the cache cleaning frequency in milliseconds.
/// cleaning frequency in millioseconds
///
public virtual void SetCleanThreadSleepTime(long cleanSleepTime)
{
this.cleanSleepTime = cleanSleepTime;
}
/// Returns the cached version of the filter. Allows the caller to pass up
/// a small filter but this will keep a persistent version around and allow
/// the caching filter to do its job.
///
///
/// The input filter
///
/// The cached version of the filter
///
public virtual Filter GetFilter(Filter filter)
{
lock (cache.SyncRoot)
{
FilterItem fi = null;
fi = (FilterItem) cache[(System.Int32) filter.GetHashCode()];
if (fi != null)
{
fi.timestamp = System.DateTime.Now.Ticks;
return fi.filter;
}
cache[(System.Int32) filter.GetHashCode()] = new FilterItem(this, filter);
return filter;
}
}
/// Holds the filter and the last time the filter was used, to make LRU-based
/// cache cleaning possible.
/// TODO: Clean this up when we switch to Java 1.5
///
protected internal class FilterItem
{
private void InitBlock(FilterManager enclosingInstance)
{
this.enclosingInstance = enclosingInstance;
}
private FilterManager enclosingInstance;
public FilterManager Enclosing_Instance
{
get
{
return enclosingInstance;
}
}
public Filter filter;
public long timestamp;
public FilterItem(FilterManager enclosingInstance, Filter filter)
{
InitBlock(enclosingInstance);
this.filter = filter;
this.timestamp = System.DateTime.Now.Ticks;
}
}
/// Keeps the cache from getting too big.
/// If we were using Java 1.5, we could use LinkedHashMap and we would not need this thread
/// to clean out the cache.
///
/// The SortedSet sortedFilterItems is used only to sort the items from the cache,
/// so when it's time to clean up we have the TreeSet sort the FilterItems by
/// timestamp.
///
/// Removes 1.5 * the numbers of items to make the cache smaller.
/// For example:
/// If cache clean size is 10, and the cache is at 15, we would remove (15 - 10) * 1.5 = 7.5 round up to 8.
/// This way we clean the cache a bit more, and avoid having the cache cleaner having to do it frequently.
///
protected internal class FilterCleaner : IThreadRunnable
{
private class AnonymousClassComparator : System.Collections.Generic.IComparer