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CacheInvalidator.d

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00001 /*******************************************************************************
00002 
00003         @file CacheInvalidator.d
00004         
00005         Copyright (C) 2004 Kris Bell
00006         
00007         This software is provided 'as-is', without any express or implied
00008         warranty. In no event will the authors be held liable for damages
00009         of any kind arising from the use of this software.
00010         
00011         Permission is hereby granted to anyone to use this software for any 
00012         purpose, including commercial applications, and to alter it and/or 
00013         redistribute it freely, subject to the following restrictions:
00014         
00015         1. The origin of this software must not be misrepresented; you must 
00016            not claim that you wrote the original software. If you use this 
00017            software in a product, an acknowledgment within documentation of 
00018            said product would be appreciated but is not required.
00019 
00020         2. Altered source versions must be plainly marked as such, and must 
00021            not be misrepresented as being the original software.
00022 
00023         3. This notice may not be removed or altered from any distribution
00024            of the source.
00025 
00026 
00027                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00028 
00029 
00030         @version        Initial version, July 2004      
00031         @author         Kris
00032 
00033 
00034 *******************************************************************************/
00035 
00036 module mango.cluster.CacheInvalidator;
00037 
00038 private import  mango.cache.Payload;
00039 
00040 public  import  mango.cluster.Client;
00041 
00042 /*******************************************************************************
00043 
00044         Utility class to invalidate specific cache entries across a 
00045         network. Any active CacheInvalidatee objects listening upon
00046         the channel specified for this class will "wake up" whenever
00047         the invalidate() method is invoked.
00048 
00049 *******************************************************************************/
00050 
00051 class CacheInvalidator : Client
00052 {
00053         private InvalidatorPayload filter;
00054 
00055         /***********************************************************************
00056 
00057                 Construct an invalidator on the specified channel. Only
00058                 those CacheInvalidatee instances configured for the same
00059                 channel will be listening to this invalidator.
00060 
00061         ***********************************************************************/
00062         
00063         this (ICluster cluster, char[] channel)
00064         in {
00065            assert (channel.length);
00066            }
00067         body
00068         {
00069                 super (cluster, channel);
00070 
00071                 // this is what we'll send as an invalidation notification ...
00072                 this.filter = new InvalidatorPayload;
00073         }
00074 
00075         /***********************************************************************
00076 
00077                 Invalidate all network cache instances on this channel
00078                 using the specified key. When 'timeLimit' is specified, 
00079                 only those cache entries with a time lesser or equal to
00080                 that specified will be removed. This is often useful if 
00081                 you wish to avoid invalidating a cache (local or remote)
00082                 that has just been updated; simply pass the time value
00083                 of the 'old' IPayload as the argument.
00084 
00085                 Note that this is asynchronous! An invalidation is just
00086                 a request to remove the item within a short time period.
00087                 If you need the entry removed synchronously, you should
00088                 use the NetworkCache extract() method instead.
00089 
00090         ***********************************************************************/
00091         
00092         void invalidate (char[] key, ulong timeLimit = ulong.max)
00093         in {
00094            assert (key.length);
00095            }
00096         body
00097         {
00098                 filter.setText (key);
00099                 filter.setTimeout (timeLimit);
00100 
00101                 // broadcast a message across the cluster
00102                 getCluster.broadcast (getChannel, filter);
00103         }
00104 }
00105 
00106 
00107 /*******************************************************************************
00108 
00109 *******************************************************************************/
00110 
00111 private class InvalidatorPayload : Payload
00112 {
00113         private char[]                    text;
00114         private ulong                     timeout;
00115 
00116         private InvalidatorPayload        next;   
00117         private static InvalidatorPayload freelist;
00118 
00119         private import mango.io.PickleRegistry;
00120 
00121         /***********************************************************************
00122         
00123                 Register this class for pickling, so we can resurrect
00124                 instances when they arrive on a network datagram.
00125 
00126         ***********************************************************************/
00127 
00128         static this ()
00129         {
00130                 PickleRegistry.enroll (new InvalidatorPayload);
00131         }
00132 
00133         /***********************************************************************
00134 
00135                 Allocate a Payload from a list rather than creating a new one
00136 
00137         ***********************************************************************/
00138 
00139         synchronized InvalidatorPayload create ()
00140         {  
00141                 InvalidatorPayload s;
00142         
00143                 if (freelist)
00144                    {
00145                    s = freelist;
00146                    freelist = s.next;
00147                    }
00148                 else
00149                    s = new InvalidatorPayload;
00150                 return s;
00151         }
00152 
00153         /***********************************************************************
00154 
00155         ***********************************************************************/
00156 
00157         char[] getText ()
00158         {
00159                 return text;
00160         }
00161 
00162         /***********************************************************************
00163 
00164         ***********************************************************************/
00165 
00166         void setText (char[] text)
00167         in {
00168            assert (text.length);
00169            }
00170         body
00171         {
00172                 this.text = text;
00173         }
00174 
00175         /***********************************************************************
00176 
00177                 Set the identifier of the cache that should not be touched
00178                 by an invalidation broadcast. This is typically a local
00179                 cache on the machine originating the invalidation; without
00180                 the ability to guard against local invalidation, the cache
00181                 entry that was just added locally would be removed along
00182                 with others across the cluster. The alternative would be
00183                 to invalidate before addding, but that approach can quickly 
00184                 become complicated by timing issues.
00185 
00186         ***********************************************************************/
00187 
00188         void setTimeout (ulong olderThan)
00189         {
00190                 timeout = olderThan;
00191         }
00192 
00193         /***********************************************************************
00194 
00195         ***********************************************************************/
00196 
00197         ulong getTimeout ()
00198         {
00199                 return timeout;
00200         }
00201 
00202         /***********************************************************************
00203 
00204                 Return this Payload to the free-list
00205 
00206         ***********************************************************************/
00207 
00208         synchronized void destroy ()
00209         {
00210                 next = freelist;
00211                 freelist = this;
00212         }
00213 
00214         /***********************************************************************
00215 
00216         ***********************************************************************/
00217 
00218         void write (IWriter writer)
00219         {
00220                 super.write (writer);
00221                 writer.put  (timeout).put(text);
00222         }
00223 
00224         /***********************************************************************
00225 
00226                 Read our attributes, after telling our superclass to do
00227                 likewise. The order of this is important with respect to
00228                 inheritance, such that a subclass and superclass may be 
00229                 populated in isolation where appropriate.
00230 
00231                 Note that we slice our text attribute, rather than copying
00232                 it. Since this class is temporal we can forego allocation
00233                 of memory, and just map it directly from the input buffer. 
00234 
00235         ***********************************************************************/
00236 
00237         void read (IReader reader)
00238         {
00239                 super.read (reader);
00240                 reader.get (timeout).get(text); 
00241         }
00242 
00243         /***********************************************************************
00244 
00245         ***********************************************************************/
00246 
00247         char[] getGuid ()
00248         {
00249                 return this.classinfo.name;
00250         }
00251 }
00252 
00253 

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