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 package com.sun.grizzly.connectioncache.impl.transport;

 import com.sun.grizzly.connectioncache.spi.concurrent.ConcurrentQueue;

 import com.sun.grizzly.connectioncache.spi.transport.ConnectionCache;

 import java.io.Closeable;

 import java.util.logging.Logger ;

 import java.util.logging.Level ;

 public abstract class ConnectionCacheBase<C extends Closeable> 

     implements ConnectionCache<C> {

     // A name for this instance, provided for convenience.

     private final String cacheType ;

     // Log to this logger if FINER is enabled.

     protected final Logger logger ;

     // Configuration data

     // XXX we may want this data to be dynamically re-configurable

     private final int highWaterMark ;                // Maximum number of 

                                                 // connections before we start 

                                                 // closing idle connections

     private final int numberToReclaim ;                // How many connections to 

                                                 // reclaim at once

     // MUST be initialized in a subclass

     protected ConcurrentQueue<C> reclaimableConnections = null ;

     protected boolean debug() {

         return logger.isLoggable( Level.FINER ) ;

     }

     public final String getCacheType() {

         return cacheType ;

     }

     public final int numberToReclaim() {

         return numberToReclaim ;

     }

     public final int highWaterMark() {

         return highWaterMark ;

     }

     // The name of this class, which is implemented in the subclass.

     // I could derive this from this.getClass().getClassName(), but

     // this is easier.

     protected abstract String thisClassName() ;

     ConnectionCacheBase( final String cacheType, 

         final int highWaterMark, final int numberToReclaim, 

         final Logger logger ) {

         if (cacheType == null)

             throw new IllegalArgumentException( "cacheType must not be null" ) ;

         if (highWaterMark < 0)

             throw new IllegalArgumentException( "highWaterMark must be non-negative" ) ;

         if (numberToReclaim < 1)

             throw new IllegalArgumentException( "numberToReclaim must be at least 1" ) ;

         if (logger == null)

             throw new IllegalArgumentException( "logger must not be null" ) ;

         this.cacheType = cacheType ;

         this.logger = logger ;

         this.highWaterMark = highWaterMark ;

         this.numberToReclaim = numberToReclaim ;

     }

     protected final void dprint(final String msg) {

         logger.finer(thisClassName() + msg);

     }

     public String toString() {

         return thisClassName() + "[" 

             + getCacheType() + "]";

     }

     public void dprintStatistics() {

         dprint( ".stats:"

                + " idle=" + numberOfIdleConnections() 

                + " reclaimable=" + numberOfReclaimableConnections() 

                + " busy=" + numberOfBusyConnections() 

                + " total=" + numberOfConnections() 

                + " (" 

                + highWaterMark() + "/"

                + numberToReclaim() 

                + ")");

     }

     /** Reclaim some idle cached connections.  Will never 

      * close a connection that is busy.

      * @return  any connections reclaimed, (yes or no)

      */

     protected boolean reclaim() {

         if (debug())

             dprint( ".reclaim: starting" ) ;

         int ctr = 0 ;

         while (ctr < numberToReclaim()) {

             C candidate = reclaimableConnections.poll() ;

             if (candidate == null)

                 // If we have closed all idle connections, we must stop 

                 // reclaiming.

                 break ;

             if (debug())

                 dprint( ".reclaim: closing connection " + candidate ) ;

             try {

                 close( candidate ) ;            

             } catch (RuntimeException exc) {

                 if (debug())

                     dprint( ".reclaim: caught exception on close: " + exc ) ;

                 throw exc ;

             }

             ctr++ ;

         }

         if (debug())

             dprint( ".reclaim: reclaimed " + ctr + " connection(s)" ) ;

         return ctr > 0 ;

     }

 }