aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/OpenSim/Region/CoreModules/Asset/FlotsamAssetCache.cs
blob: cef8029cb83df397249ff5cfeb1cc1dc7c7dba80 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

// Uncomment to make asset Get requests for existing 
// #define WAIT_ON_INPROGRESS_REQUESTS

using System;
using System.IO;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Threading;
using System.Timers;

using log4net;
using Nini.Config;
using Mono.Addins;
using OpenMetaverse;

using OpenSim.Framework;
using OpenSim.Framework.Console;
using OpenSim.Region.Framework.Interfaces;
using OpenSim.Region.Framework.Scenes;
using OpenSim.Services.Interfaces;


//[assembly: Addin("FlotsamAssetCache", "1.1")]
//[assembly: AddinDependency("OpenSim", "0.5")]

namespace OpenSim.Region.CoreModules.Asset
{
    [Extension(Path = "/OpenSim/RegionModules", NodeName = "RegionModule")]
    public class FlotsamAssetCache : ISharedRegionModule, IImprovedAssetCache, IAssetService
    {
        private static readonly ILog m_log =
                LogManager.GetLogger(
                MethodBase.GetCurrentMethod().DeclaringType);

        private bool m_Enabled;

        private const string m_ModuleName = "FlotsamAssetCache";
        private const string m_DefaultCacheDirectory = "./assetcache";
        private string m_CacheDirectory = m_DefaultCacheDirectory;

        private readonly List<char> m_InvalidChars = new List<char>();

        private int m_LogLevel = 0;
        private ulong m_HitRateDisplay = 100; // How often to display hit statistics, given in requests

        private static ulong m_Requests;
        private static ulong m_RequestsForInprogress;
        private static ulong m_DiskHits;
        private static ulong m_MemoryHits;
        private static double m_HitRateMemory;
        private static double m_HitRateFile;

#if WAIT_ON_INPROGRESS_REQUESTS
        private Dictionary<string, ManualResetEvent> m_CurrentlyWriting = new Dictionary<string, ManualResetEvent>();
        private int m_WaitOnInprogressTimeout = 3000;
#else
        private HashSet<string> m_CurrentlyWriting = new HashSet<string>();
#endif

        private bool m_FileCacheEnabled = true;

        private ExpiringCache<string, AssetBase> m_MemoryCache;
        private bool m_MemoryCacheEnabled = false;

        // Expiration is expressed in hours.
        private const double m_DefaultMemoryExpiration = 2;
        private const double m_DefaultFileExpiration = 48;
        private TimeSpan m_MemoryExpiration = TimeSpan.FromHours(m_DefaultMemoryExpiration);
        private TimeSpan m_FileExpiration = TimeSpan.FromHours(m_DefaultFileExpiration);
        private TimeSpan m_FileExpirationCleanupTimer = TimeSpan.FromHours(0.166);

        private static int m_CacheDirectoryTiers = 1;
        private static int m_CacheDirectoryTierLen = 3;
        private static int m_CacheWarnAt = 30000;

        private System.Timers.Timer m_CacheCleanTimer;

        private IAssetService m_AssetService;
        private List<Scene> m_Scenes = new List<Scene>();

        public FlotsamAssetCache()
        {
            m_InvalidChars.AddRange(Path.GetInvalidPathChars());
            m_InvalidChars.AddRange(Path.GetInvalidFileNameChars());
        }

        public Type ReplaceableInterface 
        {
            get { return null; }
        }

        public string Name
        {
            get { return m_ModuleName; }
        }

        public void Initialise(IConfigSource source)
        {
            IConfig moduleConfig = source.Configs["Modules"];
            
            if (moduleConfig != null)
            {
                string name = moduleConfig.GetString("AssetCaching", String.Empty);

                if (name == Name)
                {
                    m_MemoryCache = new ExpiringCache<string, AssetBase>();
                    m_Enabled = true;

                    m_log.InfoFormat("[FLOTSAM ASSET CACHE]: {0} enabled", this.Name);

                    IConfig assetConfig = source.Configs["AssetCache"];
                    if (assetConfig == null)
                    {
                        m_log.Debug(
                           "[FLOTSAM ASSET CACHE]: AssetCache section missing from config (not copied config-include/FlotsamCache.ini.example?  Using defaults.");
                    }
                    else
                    {
                        m_FileCacheEnabled = assetConfig.GetBoolean("FileCacheEnabled", m_FileCacheEnabled);
                        m_CacheDirectory = assetConfig.GetString("CacheDirectory", m_DefaultCacheDirectory);

                        m_MemoryCacheEnabled = assetConfig.GetBoolean("MemoryCacheEnabled", m_MemoryCacheEnabled);
                        m_MemoryExpiration = TimeSpan.FromHours(assetConfig.GetDouble("MemoryCacheTimeout", m_DefaultMemoryExpiration));
    
    #if WAIT_ON_INPROGRESS_REQUESTS
                        m_WaitOnInprogressTimeout = assetConfig.GetInt("WaitOnInprogressTimeout", 3000);
    #endif
    
                        m_LogLevel = assetConfig.GetInt("LogLevel", m_LogLevel);
                        m_HitRateDisplay = (ulong)assetConfig.GetLong("HitRateDisplay", (long)m_HitRateDisplay);

                        m_FileExpiration = TimeSpan.FromHours(assetConfig.GetDouble("FileCacheTimeout", m_DefaultFileExpiration));
                        m_FileExpirationCleanupTimer
                            = TimeSpan.FromHours(
                                assetConfig.GetDouble("FileCleanupTimer", m_FileExpirationCleanupTimer.TotalHours));

                        m_CacheDirectoryTiers = assetConfig.GetInt("CacheDirectoryTiers", m_CacheDirectoryTiers);
                        m_CacheDirectoryTierLen = assetConfig.GetInt("CacheDirectoryTierLength", m_CacheDirectoryTierLen);

                        m_CacheWarnAt = assetConfig.GetInt("CacheWarnAt", m_CacheWarnAt);
                    }

                    m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Cache Directory {0}", m_CacheDirectory);

                    if (m_FileCacheEnabled && (m_FileExpiration > TimeSpan.Zero) && (m_FileExpirationCleanupTimer > TimeSpan.Zero))
                    {
                        m_CacheCleanTimer = new System.Timers.Timer(m_FileExpirationCleanupTimer.TotalMilliseconds);
                        m_CacheCleanTimer.AutoReset = true;
                        m_CacheCleanTimer.Elapsed += CleanupExpiredFiles;
                        lock (m_CacheCleanTimer)
                            m_CacheCleanTimer.Start();
                    }

                    if (m_CacheDirectoryTiers < 1)
                    {
                        m_CacheDirectoryTiers = 1;
                    }
                    else if (m_CacheDirectoryTiers > 3)
                    {
                        m_CacheDirectoryTiers = 3;
                    }

                    if (m_CacheDirectoryTierLen < 1)
                    {
                        m_CacheDirectoryTierLen = 1;
                    }
                    else if (m_CacheDirectoryTierLen > 4)
                    {
                        m_CacheDirectoryTierLen = 4;
                    }

                    MainConsole.Instance.Commands.AddCommand("Assets", true, "fcache status", "fcache status", "Display cache status", HandleConsoleCommand);
                    MainConsole.Instance.Commands.AddCommand("Assets", true, "fcache clear",  "fcache clear [file] [memory]", "Remove all assets in the cache.  If file or memory is specified then only this cache is cleared.", HandleConsoleCommand);
                    MainConsole.Instance.Commands.AddCommand("Assets", true, "fcache assets", "fcache assets", "Attempt a deep scan and cache of all assets in all scenes", HandleConsoleCommand);
                    MainConsole.Instance.Commands.AddCommand("Assets", true, "fcache expire", "fcache expire <datetime>", "Purge cached assets older then the specified date/time", HandleConsoleCommand);
                }
            }
        }

        public void PostInitialise()
        {
        }

        public void Close()
        {
        }

        public void AddRegion(Scene scene)
        {
            if (m_Enabled)
            {
                scene.RegisterModuleInterface<IImprovedAssetCache>(this);
                m_Scenes.Add(scene);

                if (m_AssetService == null)
                {
                    m_AssetService = scene.RequestModuleInterface<IAssetService>();
                }
            }
        }

        public void RemoveRegion(Scene scene)
        {
            if (m_Enabled)
            {
                scene.UnregisterModuleInterface<IImprovedAssetCache>(this);
                m_Scenes.Remove(scene);
            }
        }

        public void RegionLoaded(Scene scene)
        {
        }

        ////////////////////////////////////////////////////////////
        // IImprovedAssetCache
        //

        private void UpdateMemoryCache(string key, AssetBase asset)
        {
            m_MemoryCache.AddOrUpdate(key, asset, m_MemoryExpiration);
        }

        private void UpdateFileCache(string key, AssetBase asset)
        {
            // TODO: Spawn this off to some seperate thread to do the actual writing
            if (asset != null)
            {
                string filename = GetFileName(key);

                try
                {
                    // If the file is already cached, don't cache it, just touch it so access time is updated
                    if (File.Exists(filename))
                    {
                        // We don't really want to know about sharing
                        // violations here. If the file is locked, then
                        // the other thread has updated the time for us.
                        try
                        {
                            lock (m_CurrentlyWriting)
                            {
                                if (!m_CurrentlyWriting.Contains(filename))
                                    File.SetLastAccessTime(filename, DateTime.Now);
                            }
                        }
                        catch
                        {
                        }
                    } else {

                        // Once we start writing, make sure we flag that we're writing
                        // that object to the cache so that we don't try to write the 
                        // same file multiple times.
                        lock (m_CurrentlyWriting)
                        {
#if WAIT_ON_INPROGRESS_REQUESTS
                            if (m_CurrentlyWriting.ContainsKey(filename))
                            {
                                return;
                            }
                            else
                            {
                                m_CurrentlyWriting.Add(filename, new ManualResetEvent(false));
                            }

#else
                            if (m_CurrentlyWriting.Contains(filename))
                            {
                                return;
                            }
                            else
                            {
                                m_CurrentlyWriting.Add(filename);
                            }
#endif

                        }

                        Util.FireAndForget(
                            delegate { WriteFileCache(filename, asset); });
                    }
                }
                catch (Exception e)
                {
                    m_log.ErrorFormat(
                        "[FLOTSAM ASSET CACHE]: Failed to update cache for asset {0}.  Exception {1} {2}",
                        asset.ID, e.Message, e.StackTrace);
                }
            }
        }

        public void Cache(AssetBase asset)
        {
            // TODO: Spawn this off to some seperate thread to do the actual writing
            if (asset != null)
            {
                //m_log.DebugFormat("[FLOTSAM ASSET CACHE]: Caching asset with id {0}", asset.ID);

                if (m_MemoryCacheEnabled)
                    UpdateMemoryCache(asset.ID, asset);

                if (m_FileCacheEnabled)
                    UpdateFileCache(asset.ID, asset);
            }
        }

        /// <summary>
        /// Try to get an asset from the in-memory cache.
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        private AssetBase GetFromMemoryCache(string id)
        {
            AssetBase asset = null;

            if (m_MemoryCache.TryGetValue(id, out asset))
                m_MemoryHits++;

            return asset;
        }

        /// <summary>
        /// Try to get an asset from the file cache.
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        private AssetBase GetFromFileCache(string id)
        {
            AssetBase asset = null;

            string filename = GetFileName(id);
            if (File.Exists(filename))
            {
                FileStream stream = null;
                try
                {
                    stream = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
                    BinaryFormatter bformatter = new BinaryFormatter();

                    asset = (AssetBase)bformatter.Deserialize(stream);

                    m_DiskHits++;
                }
                catch (System.Runtime.Serialization.SerializationException e)
                {
                    m_log.ErrorFormat(
                        "[FLOTSAM ASSET CACHE]: Failed to get file {0} for asset {1}.  Exception {2} {3}",
                        filename, id, e.Message, e.StackTrace);

                    // If there was a problem deserializing the asset, the asset may
                    // either be corrupted OR was serialized under an old format
                    // {different version of AssetBase} -- we should attempt to
                    // delete it and re-cache
                    File.Delete(filename);
                }
                catch (Exception e)
                {
                    m_log.ErrorFormat(
                        "[FLOTSAM ASSET CACHE]: Failed to get file {0} for asset {1}.  Exception {2} {3}",
                        filename, id, e.Message, e.StackTrace);
                }
                finally
                {
                    if (stream != null)
                        stream.Close();
                }
            }

#if WAIT_ON_INPROGRESS_REQUESTS
            // Check if we're already downloading this asset.  If so, try to wait for it to
            // download.
            if (m_WaitOnInprogressTimeout > 0)
            {
                m_RequestsForInprogress++;

                ManualResetEvent waitEvent;
                if (m_CurrentlyWriting.TryGetValue(filename, out waitEvent))
                {
                    waitEvent.WaitOne(m_WaitOnInprogressTimeout);
                    return Get(id);
                }
            }
#else
            // Track how often we have the problem that an asset is requested while
            // it is still being downloaded by a previous request.
            if (m_CurrentlyWriting.Contains(filename))
            {
                m_RequestsForInprogress++;
            }
#endif
            return asset;
        }

        public AssetBase Get(string id)
        {
            m_Requests++;

            AssetBase asset = null;

            if (m_MemoryCacheEnabled)
                asset = GetFromMemoryCache(id);

            if (asset == null && m_FileCacheEnabled)
            {
                asset = GetFromFileCache(id);

                if (m_MemoryCacheEnabled && asset != null)
                    UpdateMemoryCache(id, asset);
            }

            if (((m_LogLevel >= 1)) && (m_HitRateDisplay != 0) && (m_Requests % m_HitRateDisplay == 0))
            {
                m_HitRateFile = (double)m_DiskHits / m_Requests * 100.0;

                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Cache Get :: {0} :: {1}", id, asset == null ? "Miss" : "Hit");
                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: File Hit Rate {0}% for {1} requests", m_HitRateFile.ToString("0.00"), m_Requests);

                if (m_MemoryCacheEnabled)
                {
                    m_HitRateMemory = (double)m_MemoryHits / m_Requests * 100.0;
                    m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Memory Hit Rate {0}% for {1} requests", m_HitRateMemory.ToString("0.00"), m_Requests);
                }

                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: {0} unnessesary requests due to requests for assets that are currently downloading.", m_RequestsForInprogress);
            }

            return asset;
        }

        public AssetBase GetCached(string id)
        {
            return Get(id);
        }

        public void Expire(string id)
        {
            if (m_LogLevel >= 2)
                m_log.DebugFormat("[FLOTSAM ASSET CACHE]: Expiring Asset {0}", id);

            try
            {
                if (m_FileCacheEnabled)
                {
                    string filename = GetFileName(id);
                    if (File.Exists(filename))
                    {
                        File.Delete(filename);
                    }
                }

                if (m_MemoryCacheEnabled)
                    m_MemoryCache.Remove(id);
            }
            catch (Exception e)
            {
                m_log.ErrorFormat(
                    "[FLOTSAM ASSET CACHE]: Failed to expire cached file {0}.  Exception {1} {2}",
                    id, e.Message, e.StackTrace);
            }
        }

        public void Clear()
        {
            if (m_LogLevel >= 2)
                m_log.Debug("[FLOTSAM ASSET CACHE]: Clearing caches.");

            if (m_FileCacheEnabled)
            {
                foreach (string dir in Directory.GetDirectories(m_CacheDirectory))
                {
                    Directory.Delete(dir);
                }
            }

            if (m_MemoryCacheEnabled)
                m_MemoryCache.Clear();
        }

        private void CleanupExpiredFiles(object source, ElapsedEventArgs e)
        {
            if (m_LogLevel >= 2)
                m_log.DebugFormat("[FLOTSAM ASSET CACHE]: Checking for expired files older then {0}.", m_FileExpiration);

            // Purge all files last accessed prior to this point
            DateTime purgeLine = DateTime.Now - m_FileExpiration;

            // An asset cache may contain local non-temporary assets that are not in the asset service.  Therefore,
            // before cleaning up expired files we must scan the objects in the scene to make sure that we retain
            // such local assets if they have not been recently accessed.
            TouchAllSceneAssets(false);

            foreach (string dir in Directory.GetDirectories(m_CacheDirectory))
            {
                CleanExpiredFiles(dir, purgeLine);
            }
        }

        /// <summary>
        /// Recurses through specified directory checking for asset files last 
        /// accessed prior to the specified purge line and deletes them.  Also 
        /// removes empty tier directories.
        /// </summary>
        /// <param name="dir"></param>
        /// <param name="purgeLine"></param>
        private void CleanExpiredFiles(string dir, DateTime purgeLine)
        {
            foreach (string file in Directory.GetFiles(dir))
            {
                if (File.GetLastAccessTime(file) < purgeLine)
                {
                    File.Delete(file);
                }
            }

            // Recurse into lower tiers
            foreach (string subdir in Directory.GetDirectories(dir))
            {
                CleanExpiredFiles(subdir, purgeLine);
            }

            // Check if a tier directory is empty, if so, delete it
            int dirSize = Directory.GetFiles(dir).Length + Directory.GetDirectories(dir).Length;
            if (dirSize == 0)
            {
                Directory.Delete(dir);
            }
            else if (dirSize >= m_CacheWarnAt)
            {
                m_log.WarnFormat("[FLOTSAM ASSET CACHE]: Cache folder exceeded CacheWarnAt limit {0} {1}.  Suggest increasing tiers, tier length, or reducing cache expiration", dir, dirSize);
            }
        }

        /// <summary>
        /// Determines the filename for an AssetID stored in the file cache
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        private string GetFileName(string id)
        {
            // Would it be faster to just hash the darn thing?
            foreach (char c in m_InvalidChars)
            {
                id = id.Replace(c, '_');
            }

            string path = m_CacheDirectory;
            for (int p = 1; p <= m_CacheDirectoryTiers; p++)
            {
                string pathPart = id.Substring((p - 1) * m_CacheDirectoryTierLen, m_CacheDirectoryTierLen);
                path = Path.Combine(path, pathPart);
            }

            return Path.Combine(path, id);
        }

        /// <summary>
        /// Writes a file to the file cache, creating any nessesary 
        /// tier directories along the way
        /// </summary>
        /// <param name="filename"></param>
        /// <param name="asset"></param>
        private void WriteFileCache(string filename, AssetBase asset)
        {
            Stream stream = null;

            // Make sure the target cache directory exists
            string directory = Path.GetDirectoryName(filename);

            // Write file first to a temp name, so that it doesn't look 
            // like it's already cached while it's still writing.
            string tempname = Path.Combine(directory, Path.GetRandomFileName());

            try
            {
                try
                {
                    if (!Directory.Exists(directory))
                    {
                        Directory.CreateDirectory(directory);
                    }
    
                    stream = File.Open(tempname, FileMode.Create);
                    BinaryFormatter bformatter = new BinaryFormatter();
                    bformatter.Serialize(stream, asset);
                }
                catch (IOException e)
                {
                    m_log.ErrorFormat(
                        "[FLOTSAM ASSET CACHE]: Failed to write asset {0} to temporary location {1} (final {2}) on cache in {3}.  Exception {4} {5}.",
                        asset.ID, tempname, filename, directory, e.Message, e.StackTrace);

                    return;
                }
                finally
                {
                    if (stream != null)
                        stream.Close();
                }

                try
                {
                    // Now that it's written, rename it so that it can be found.
                    //
    //                File.Copy(tempname, filename, true);
    //                File.Delete(tempname);
                    //
                    // For a brief period, this was done as a separate copy and then temporary file delete operation to
                    // avoid an IOException caused by move if some competing thread had already written the file.
                    // However, this causes exceptions on Windows when other threads attempt to read a file
                    // which is still being copied.  So instead, go back to moving the file and swallow any IOException.
                    //
                    // This situation occurs fairly rarely anyway.  We assume in this that moves are atomic on the
                    // filesystem.
                    File.Move(tempname, filename);
    
                    if (m_LogLevel >= 2)
                        m_log.DebugFormat("[FLOTSAM ASSET CACHE]: Cache Stored :: {0}", asset.ID);
                }
                catch (IOException)
                {
                    // If we see an IOException here it's likely that some other competing thread has written the
                    // cache file first, so ignore.  Other IOException errors (e.g. filesystem full) should be
                    // signally by the earlier temporary file writing code.
                }
            }
            finally
            {
                // Even if the write fails with an exception, we need to make sure
                // that we release the lock on that file, otherwise it'll never get
                // cached
                lock (m_CurrentlyWriting)
                {
#if WAIT_ON_INPROGRESS_REQUESTS
                    ManualResetEvent waitEvent;
                    if (m_CurrentlyWriting.TryGetValue(filename, out waitEvent))
                    {
                        m_CurrentlyWriting.Remove(filename);
                        waitEvent.Set();
                    }
#else
                    m_CurrentlyWriting.Remove(filename);
#endif
                }
            }
        }

        /// <summary>
        /// Scan through the file cache, and return number of assets currently cached.
        /// </summary>
        /// <param name="dir"></param>
        /// <returns></returns>
        private int GetFileCacheCount(string dir)
        {
            int count = Directory.GetFiles(dir).Length;

            foreach (string subdir in Directory.GetDirectories(dir))
            {
                count += GetFileCacheCount(subdir);
            }

            return count;
        }

        /// <summary>
        /// This notes the last time the Region had a deep asset scan performed on it.
        /// </summary>
        /// <param name="RegionID"></param>
        private void StampRegionStatusFile(UUID RegionID)
        {
            string RegionCacheStatusFile = Path.Combine(m_CacheDirectory, "RegionStatus_" + RegionID.ToString() + ".fac");
            if (File.Exists(RegionCacheStatusFile))
            {
                File.SetLastWriteTime(RegionCacheStatusFile, DateTime.Now);
            }
            else
            {
                File.WriteAllText(RegionCacheStatusFile, "Please do not delete this file unless you are manually clearing your Flotsam Asset Cache.");
            }
        }

        /// <summary>
        /// Iterates through all Scenes, doing a deep scan through assets 
        /// to update the access time of all assets present in the scene or referenced by assets
        /// in the scene.
        /// </summary>
        /// <param name="storeUncached">
        /// If true, then assets scanned which are not found in cache are added to the cache.
        /// </param>
        /// <returns>Number of distinct asset references found in the scene.</returns>
        private int TouchAllSceneAssets(bool storeUncached)
        {
            UuidGatherer gatherer = new UuidGatherer(m_AssetService);

            Dictionary<UUID, AssetType> assets = new Dictionary<UUID, AssetType>();
            foreach (Scene s in m_Scenes)
            {
                StampRegionStatusFile(s.RegionInfo.RegionID);

                s.ForEachSOG(delegate(SceneObjectGroup e)
                {
                    gatherer.GatherAssetUuids(e, assets);
                });
            }

            foreach (UUID assetID in assets.Keys)
            {
                string filename = GetFileName(assetID.ToString());

                if (File.Exists(filename))
                {
                    File.SetLastAccessTime(filename, DateTime.Now);
                }
                else if (storeUncached)
                {
                    m_AssetService.Get(assetID.ToString());
                }
            }

            return assets.Keys.Count;
        }

        /// <summary>
        /// Deletes all cache contents
        /// </summary>
        private void ClearFileCache()
        {
            foreach (string dir in Directory.GetDirectories(m_CacheDirectory))
            {
                try
                {
                    Directory.Delete(dir, true);
                }
                catch (Exception e)
                {
                    m_log.ErrorFormat(
                        "[FLOTSAM ASSET CACHE]: Couldn't clear asset cache directory {0} from {1}.  Exception {2} {3}",
                        dir, m_CacheDirectory, e.Message, e.StackTrace);
                }
            }

            foreach (string file in Directory.GetFiles(m_CacheDirectory))
            {
                try
                {
                    File.Delete(file);
                }
                catch (Exception e)
                {
                    m_log.ErrorFormat(
                        "[FLOTSAM ASSET CACHE]: Couldn't clear asset cache file {0} from {1}.  Exception {1} {2}",
                        file, m_CacheDirectory, e.Message, e.StackTrace);
                }
            }
        }

        #region Console Commands
        private void HandleConsoleCommand(string module, string[] cmdparams)
        {
            if (cmdparams.Length >= 2)
            {
                string cmd = cmdparams[1];
                switch (cmd)
                {
                    case "status":
                        if (m_MemoryCacheEnabled)
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Memory Cache : {0} assets", m_MemoryCache.Count);
                        else
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Memory cache disabled");

                        if (m_FileCacheEnabled)
                        {
                            int fileCount = GetFileCacheCount(m_CacheDirectory);
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: File Cache : {0} assets", fileCount);
    
                            foreach (string s in Directory.GetFiles(m_CacheDirectory, "*.fac"))
                            {
                                m_log.Info("[FLOTSAM ASSET CACHE]: Deep scans have previously been performed on the following regions:");
    
                                string RegionID = s.Remove(0,s.IndexOf("_")).Replace(".fac","");
                                DateTime RegionDeepScanTMStamp = File.GetLastWriteTime(s);
                                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Region: {0}, {1}", RegionID, RegionDeepScanTMStamp.ToString("MM/dd/yyyy hh:mm:ss"));
                            }
                        }
                        else
                        {
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: File cache disabled");
                        }

                        break;

                    case "clear":
                        if (cmdparams.Length < 2)
                        {
                            m_log.Warn("[FLOTSAM ASSET CACHE]: Usage is fcache clear [file] [memory]");
                            break;
                        }

                        bool clearMemory = false, clearFile = false;

                        if (cmdparams.Length == 2)
                        {
                            clearMemory = true;
                            clearFile = true;
                        }
                        foreach (string s in cmdparams)
                        {
                            if (s.ToLower() == "memory")
                                clearMemory = true;
                            else if (s.ToLower() == "file")
                                clearFile = true;
                        }

                        if (clearMemory)
                        {
                            if (m_MemoryCacheEnabled)
                            {
                                m_MemoryCache.Clear();
                                m_log.Info("[FLOTSAM ASSET CACHE]: Memory cache cleared.");
                            }
                            else
                            {
                                m_log.Info("[FLOTSAM ASSET CACHE]: Memory cache not enabled.");
                            }
                        }
    
                        if (clearFile)
                        {
                            if (m_FileCacheEnabled)
                            {
                                ClearFileCache();
                                m_log.Info("[FLOTSAM ASSET CACHE]: File cache cleared.");
                            }
                            else
                            {
                                m_log.Info("[FLOTSAM ASSET CACHE]: File cache not enabled.");
                            }
                        }

                        break;

                    case "assets":
                        m_log.Info("[FLOTSAM ASSET CACHE]: Ensuring assets are cached for all scenes.");

                        Util.FireAndForget(delegate {
                            int assetReferenceTotal = TouchAllSceneAssets(true);
                            m_log.InfoFormat(
                                "[FLOTSAM ASSET CACHE]: Completed check with {0} assets.",
                                assetReferenceTotal);
                        });

                        break;

                    case "expire":
                        if (cmdparams.Length < 3)
                        {
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Invalid parameters for Expire, please specify a valid date & time", cmd);
                            break;
                        }

                        string s_expirationDate = "";
                        DateTime expirationDate;

                        if (cmdparams.Length > 3)
                        {
                            s_expirationDate = string.Join(" ", cmdparams, 2, cmdparams.Length - 2);
                        }
                        else
                        {
                            s_expirationDate = cmdparams[2];
                        }

                        if (!DateTime.TryParse(s_expirationDate, out expirationDate))
                        {
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: {0} is not a valid date & time", cmd);
                            break;
                        }

                        if (m_FileCacheEnabled)
                            CleanExpiredFiles(m_CacheDirectory, expirationDate);
                        else
                            m_log.InfoFormat("[FLOTSAM ASSET CACHE]: File cache not active, not clearing.");

                        break;
                    default:
                        m_log.InfoFormat("[FLOTSAM ASSET CACHE]: Unknown command {0}", cmd);
                        break;
                }
            }
            else if (cmdparams.Length == 1)
            {
                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: fcache status - Display cache status");
                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: fcache clearmem - Remove all assets cached in memory");
                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: fcache clearfile - Remove all assets cached on disk");
                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: fcache cachescenes - Attempt a deep cache of all assets in all scenes");
                m_log.InfoFormat("[FLOTSAM ASSET CACHE]: fcache <datetime> - Purge assets older then the specified date & time");
            }
        }

        #endregion

        #region IAssetService Members

        public AssetMetadata GetMetadata(string id)
        {
            AssetBase asset = Get(id);
            return asset.Metadata;
        }

        public byte[] GetData(string id)
        {
            AssetBase asset = Get(id);
            return asset.Data;
        }

        public bool Get(string id, object sender, AssetRetrieved handler)
        {
            AssetBase asset = Get(id);
            handler(id, sender, asset);
            return true;
        }

        public string Store(AssetBase asset)
        {
            if (asset.FullID == UUID.Zero)
            {
                asset.FullID = UUID.Random();
            }

            Cache(asset);

            return asset.ID;
        }

        public bool UpdateContent(string id, byte[] data)
        {
            AssetBase asset = Get(id);
            asset.Data = data;
            Cache(asset);
            return true;
        }

        public bool Delete(string id)
        {
            Expire(id);
            return true;
        }

        #endregion
    }
}