code.grnet.gr Git - pithos-ms-client/blob - trunk/Pithos.Core/Agents/PollAgent.cs

   1 #region\r
   2 /* -----------------------------------------------------------------------\r
   3  * <copyright file="PollAgent.cs" company="GRNet">\r
   4  * \r
   5  * Copyright 2011-2012 GRNET S.A. All rights reserved.\r
   6  *\r
   7  * Redistribution and use in source and binary forms, with or\r
   8  * without modification, are permitted provided that the following\r
   9  * conditions are met:\r
  10  *\r
  11  *   1. Redistributions of source code must retain the above\r
  12  *      copyright notice, this list of conditions and the following\r
  13  *      disclaimer.\r
  14  *\r
  15  *   2. Redistributions in binary form must reproduce the above\r
  16  *      copyright notice, this list of conditions and the following\r
  17  *      disclaimer in the documentation and/or other materials\r
  18  *      provided with the distribution.\r
  19  *\r
  20  *\r
  21  * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS\r
  22  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED\r
  23  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR\r
  24  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR\r
  25  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,\r
  26  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT\r
  27  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF\r
  28  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED\r
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT\r
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN\r
  31  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE\r
  32  * POSSIBILITY OF SUCH DAMAGE.\r
  33  *\r
  34  * The views and conclusions contained in the software and\r
  35  * documentation are those of the authors and should not be\r
  36  * interpreted as representing official policies, either expressed\r
  37  * or implied, of GRNET S.A.\r
  38  * </copyright>\r
  39  * -----------------------------------------------------------------------\r
  40  */\r
  41 #endregion\r
  42 \r
  43 using System.Collections.Concurrent;\r
  44 using System.ComponentModel.Composition;\r
  45 using System.Diagnostics;\r
  46 using System.Diagnostics.Contracts;\r
  47 using System.IO;\r
  48 using System.Reflection;\r
  49 using System.Threading;\r
  50 using System.Threading.Tasks;\r
  51 using Castle.ActiveRecord;\r
  52 using Pithos.Interfaces;\r
  53 using Pithos.Network;\r
  54 using log4net;\r
  55 \r
  56 namespace Pithos.Core.Agents\r
  57 {\r
  58     using System;\r
  59     using System.Collections.Generic;\r
  60     using System.Linq;\r
  61 \r
  62     /// <summary>\r
  63     /// PollAgent periodically polls the server to detect object changes. The agent retrieves a listing of all\r
  64     /// objects and compares it with a previously cached version to detect differences. \r
  65     /// New files are downloaded, missing files are deleted from the local file system and common files are compared\r
  66     /// to determine the appropriate action\r
  67     /// </summary>\r
  68     [Export]\r
  69     public class PollAgent\r
  70     {\r
  71         private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);\r
  72 \r
  73         [System.ComponentModel.Composition.Import]\r
  74         public IStatusKeeper StatusKeeper { get; set; }\r
  75 \r
  76         [System.ComponentModel.Composition.Import]\r
  77         public IPithosSettings Settings { get; set; }\r
  78 \r
  79         [System.ComponentModel.Composition.Import]\r
  80         public NetworkAgent NetworkAgent { get; set; }\r
  81 \r
  82         public IStatusNotification StatusNotification { get; set; }\r
  83 \r
  84         private bool _firstPoll = true;\r
  85 \r
  86         //The Sync Event signals a manual synchronisation\r
  87         private readonly AsyncManualResetEvent _syncEvent = new AsyncManualResetEvent();\r
  88 \r
  89         private readonly ConcurrentDictionary<string, DateTime> _lastSeen = new ConcurrentDictionary<string, DateTime>();\r
  90         private readonly ConcurrentDictionary<string, AccountInfo> _accounts = new ConcurrentDictionary<string,AccountInfo>();\r
  91 \r
  92 \r
  93         /// <summary>\r
  94         /// Start a manual synchronization\r
  95         /// </summary>\r
  96         public void SynchNow()\r
  97         {            \r
  98             _syncEvent.Set();\r
  99         }\r
 100 \r
 101         /// <summary>\r
 102         /// Remote files are polled periodically. Any changes are processed\r
 103         /// </summary>\r
 104         /// <param name="since"></param>\r
 105         /// <returns></returns>\r
 106         public async Task PollRemoteFiles(DateTime? since = null)\r
 107         {\r
 108             if (Log.IsDebugEnabled)\r
 109                 Log.DebugFormat("Polling changes after [{0}]",since);\r
 110 \r
 111             Debug.Assert(Thread.CurrentThread.IsBackground, "Polling Ended up in the main thread!");\r
 112             \r
 113 \r
 114             using (ThreadContext.Stacks["Retrieve Remote"].Push("All accounts"))\r
 115             {\r
 116                 //If this poll fails, we will retry with the same since value\r
 117                 var nextSince = since;\r
 118                 try\r
 119                 {\r
 120                     UpdateStatus(PithosStatus.PollSyncing);\r
 121 \r
 122                     var tasks = from accountInfo in _accounts.Values\r
 123                                 select ProcessAccountFiles(accountInfo, since);\r
 124 \r
 125                     var nextTimes=await TaskEx.WhenAll(tasks.ToList());\r
 126 \r
 127                     _firstPoll = false;\r
 128                     //Reschedule the poll with the current timestamp as a "since" value\r
 129 \r
 130                     if (nextTimes.Length>0)\r
 131                         nextSince = nextTimes.Min();\r
 132                     if (Log.IsDebugEnabled)\r
 133                         Log.DebugFormat("Next Poll at [{0}]",nextSince);\r
 134                 }\r
 135                 catch (Exception ex)\r
 136                 {\r
 137                     Log.ErrorFormat("Error while processing accounts\r\n{0}", ex);\r
 138                     //In case of failure retry with the same "since" value\r
 139                 }\r
 140 \r
 141                 UpdateStatus(PithosStatus.PollComplete);\r
 142                 //The multiple try blocks are required because we can't have an await call\r
 143                 //inside a finally block\r
 144                 //TODO: Find a more elegant solution for reschedulling in the event of an exception\r
 145                 try\r
 146                 {\r
 147                     //Wait for the polling interval to pass or the Sync event to be signalled\r
 148                     nextSince = await WaitForScheduledOrManualPoll(nextSince);\r
 149                 }\r
 150                 finally\r
 151                 {\r
 152                     //Ensure polling is scheduled even in case of error\r
 153                     TaskEx.Run(() => PollRemoteFiles(nextSince));                        \r
 154                 }\r
 155             }\r
 156         }\r
 157 \r
 158         /// <summary>\r
 159         /// Wait for the polling period to expire or a manual sync request\r
 160         /// </summary>\r
 161         /// <param name="since"></param>\r
 162         /// <returns></returns>\r
 163         private async Task<DateTime?> WaitForScheduledOrManualPoll(DateTime? since)\r
 164         {\r
 165             var sync = _syncEvent.WaitAsync();\r
 166             var wait = TaskEx.Delay(TimeSpan.FromSeconds(Settings.PollingInterval), NetworkAgent.CancellationToken);\r
 167             var signaledTask = await TaskEx.WhenAny(sync, wait);\r
 168 \r
 169             //Wait for network processing to finish before polling\r
 170             var pauseTask=NetworkAgent.ProceedEvent.WaitAsync();\r
 171             await TaskEx.WhenAll(signaledTask, pauseTask);\r
 172 \r
 173             //If polling is signalled by SynchNow, ignore the since tag\r
 174             if (sync.IsCompleted)\r
 175             {\r
 176                 //TODO: Must convert to AutoReset\r
 177                 _syncEvent.Reset();\r
 178                 return null;\r
 179             }\r
 180             return since;\r
 181         }\r
 182 \r
 183         public async Task<DateTime?> ProcessAccountFiles(AccountInfo accountInfo, DateTime? since = null)\r
 184         {\r
 185             if (accountInfo == null)\r
 186                 throw new ArgumentNullException("accountInfo");\r
 187             if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))\r
 188                 throw new ArgumentException("The AccountInfo.AccountPath is empty", "accountInfo");\r
 189             Contract.EndContractBlock();\r
 190 \r
 191 \r
 192             using (ThreadContext.Stacks["Retrieve Remote"].Push(accountInfo.UserName))\r
 193             {\r
 194 \r
 195                 await NetworkAgent.GetDeleteAwaiter();\r
 196 \r
 197                 Log.Info("Scheduled");\r
 198                 var client = new CloudFilesClient(accountInfo);\r
 199 \r
 200                 //We don't need to check the trash container\r
 201                 var containers = client.ListContainers(accountInfo.UserName)\r
 202                     .Where(c=>c.Name!="trash")\r
 203                     .ToList();\r
 204 \r
 205 \r
 206                 CreateContainerFolders(accountInfo, containers);\r
 207 \r
 208                 //The nextSince time fallback time is the same as the current.\r
 209                 //If polling succeeds, the next Since time will be the smallest of the maximum modification times\r
 210                 //of the shared and account objects\r
 211                 var nextSince = since;\r
 212 \r
 213                 try\r
 214                 {\r
 215                     //Wait for any deletions to finish\r
 216                     await NetworkAgent.GetDeleteAwaiter();\r
 217                     //Get the poll time now. We may miss some deletions but it's better to keep a file that was deleted\r
 218                     //than delete a file that was created while we were executing the poll                    \r
 219 \r
 220                     //Get the list of server objects changed since the last check\r
 221                     //The name of the container is passed as state in order to create a dictionary of tasks in a subsequent step\r
 222                     var listObjects = (from container in containers\r
 223                                        select Task<IList<ObjectInfo>>.Factory.StartNew(_ =>\r
 224                                              client.ListObjects(accountInfo.UserName, container.Name, since), container.Name)).ToList();\r
 225 \r
 226                     var listShared = Task<IList<ObjectInfo>>.Factory.StartNew(_ => \r
 227                         client.ListSharedObjects(since), "shared");\r
 228                     listObjects.Add(listShared);\r
 229                     var listTasks = await Task.Factory.WhenAll(listObjects.ToArray());\r
 230 \r
 231                     using (ThreadContext.Stacks["SCHEDULE"].Push("Process Results"))\r
 232                     {\r
 233                         var dict = listTasks.ToDictionary(t => t.AsyncState);\r
 234 \r
 235                         //Get all non-trash objects. Remember, the container name is stored in AsyncState\r
 236                         var remoteObjects = (from objectList in listTasks\r
 237                                             where (string)objectList.AsyncState != "trash"\r
 238                                             from obj in objectList.Result\r
 239                                             select obj).ToList();\r
 240                         \r
 241                         //Get the latest remote object modification date, only if it is after\r
 242                         //the original since date\r
 243                         nextSince = GetLatestDateAfter(nextSince, remoteObjects);\r
 244 \r
 245                         var sharedObjects = dict["shared"].Result;\r
 246                         nextSince = GetLatestDateBefore(nextSince, sharedObjects);\r
 247 \r
 248                         //DON'T process trashed files\r
 249                         //If some files are deleted and added again to a folder, they will be deleted\r
 250                         //even though they are new.\r
 251                         //We would have to check file dates and hashes to ensure that a trashed file\r
 252                         //can be deleted safely from the local hard drive.\r
 253                         /*\r
 254                         //Items with the same name, hash may be both in the container and the trash\r
 255                         //Don't delete items that exist in the container\r
 256                         var realTrash = from trash in trashObjects\r
 257                                         where\r
 258                                             !remoteObjects.Any(\r
 259                                                 info => info.Name == trash.Name && info.Hash == trash.Hash)\r
 260                                         select trash;\r
 261                         ProcessTrashedFiles(accountInfo, realTrash);\r
 262 */\r
 263 \r
 264                         var cleanRemotes = (from info in remoteObjects.Union(sharedObjects)\r
 265                                             let name = info.Name??""\r
 266                                             where !name.EndsWith(".ignore", StringComparison.InvariantCultureIgnoreCase) &&\r
 267                                                   !name.StartsWith(FolderConstants.CacheFolder + "/",\r
 268                                                                    StringComparison.InvariantCultureIgnoreCase)\r
 269                                             select info).ToList();\r
 270 \r
 271                         var differencer = _differencer.PostSnapshot(accountInfo, cleanRemotes);\r
 272 \r
 273                         ProcessDeletedFiles(accountInfo, differencer.Deleted.FilterDirectlyBelow(SelectiveUris));\r
 274 \r
 275                         // @@@ NEED To add previous state here as well, To compare with previous hash\r
 276 \r
 277                         \r
 278 \r
 279                         //Create a list of actions from the remote files\r
 280                         var allActions = MovesToActions(accountInfo,differencer.Moved.FilterDirectlyBelow(SelectiveUris))\r
 281                                         .Union(\r
 282                                         ChangesToActions(accountInfo, differencer.Changed.FilterDirectlyBelow(SelectiveUris)))\r
 283                                         .Union(\r
 284                                         CreatesToActions(accountInfo, differencer.Created.FilterDirectlyBelow(SelectiveUris)));\r
 285 \r
 286                         //And remove those that are already being processed by the agent\r
 287                         var distinctActions = allActions\r
 288                             .Except(NetworkAgent.GetEnumerable(), new LocalFileComparer())\r
 289                             .ToList();\r
 290 \r
 291                         //Queue all the actions\r
 292                         foreach (var message in distinctActions)\r
 293                         {\r
 294                             NetworkAgent.Post(message);\r
 295                         }\r
 296 \r
 297                         Log.Info("[LISTENER] End Processing");\r
 298                     }\r
 299                 }\r
 300                 catch (Exception ex)\r
 301                 {\r
 302                     Log.ErrorFormat("[FAIL] ListObjects for{0} in ProcessRemoteFiles with {1}", accountInfo.UserName, ex);\r
 303                     return nextSince;\r
 304                 }\r
 305 \r
 306                 Log.Info("[LISTENER] Finished");\r
 307                 return nextSince;\r
 308             }\r
 309         }\r
 310 \r
 311         /// <summary>\r
 312         /// Returns the latest LastModified date from the list of objects, but only if it is before\r
 313         /// than the threshold value\r
 314         /// </summary>\r
 315         /// <param name="threshold"></param>\r
 316         /// <param name="cloudObjects"></param>\r
 317         /// <returns></returns>\r
 318         private static DateTime? GetLatestDateBefore(DateTime? threshold, IList<ObjectInfo> cloudObjects)\r
 319         {\r
 320             DateTime? maxDate = null;\r
 321             if (cloudObjects!=null &&  cloudObjects.Count > 0)\r
 322                 maxDate = cloudObjects.Max(obj => obj.Last_Modified);\r
 323             if (maxDate == null || maxDate == DateTime.MinValue)\r
 324                 return threshold;\r
 325             if (threshold == null || threshold == DateTime.MinValue || threshold > maxDate)\r
 326                 return maxDate;\r
 327             return threshold;\r
 328         }\r
 329 \r
 330         /// <summary>\r
 331         /// Returns the latest LastModified date from the list of objects, but only if it is after\r
 332         /// the threshold value\r
 333         /// </summary>\r
 334         /// <param name="threshold"></param>\r
 335         /// <param name="cloudObjects"></param>\r
 336         /// <returns></returns>\r
 337         private static DateTime? GetLatestDateAfter(DateTime? threshold, IList<ObjectInfo> cloudObjects)\r
 338         {\r
 339             DateTime? maxDate = null;\r
 340             if (cloudObjects!=null &&  cloudObjects.Count > 0)\r
 341                 maxDate = cloudObjects.Max(obj => obj.Last_Modified);\r
 342             if (maxDate == null || maxDate == DateTime.MinValue)\r
 343                 return threshold;\r
 344             if (threshold == null || threshold == DateTime.MinValue || threshold < maxDate)\r
 345                 return maxDate;\r
 346             return threshold;\r
 347         }\r
 348 \r
 349         readonly AccountsDifferencer _differencer = new AccountsDifferencer();\r
 350         private List<Uri> _selectiveUris=new List<Uri>();\r
 351 \r
 352         /// <summary>\r
 353         /// Deletes local files that are not found in the list of cloud files\r
 354         /// </summary>\r
 355         /// <param name="accountInfo"></param>\r
 356         /// <param name="cloudFiles"></param>\r
 357         private void ProcessDeletedFiles(AccountInfo accountInfo, IEnumerable<ObjectInfo> cloudFiles)\r
 358         {\r
 359             if (accountInfo == null)\r
 360                 throw new ArgumentNullException("accountInfo");\r
 361             if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))\r
 362                 throw new ArgumentException("The AccountInfo.AccountPath is empty", "accountInfo");\r
 363             if (cloudFiles == null)\r
 364                 throw new ArgumentNullException("cloudFiles");\r
 365             Contract.EndContractBlock();\r
 366 \r
 367             //On the first run\r
 368             if (_firstPoll)\r
 369             {\r
 370                 //Only consider files that are not being modified, ie they are in the Unchanged state            \r
 371                 var deleteCandidates = FileState.Queryable.Where(state =>\r
 372                     state.FilePath.StartsWith(accountInfo.AccountPath)\r
 373                     && state.FileStatus == FileStatus.Unchanged).ToList();\r
 374 \r
 375 \r
 376                 //TODO: filesToDelete must take into account the Others container            \r
 377                 var filesToDelete = (from deleteCandidate in deleteCandidates\r
 378                                      let localFile = FileInfoExtensions.FromPath(deleteCandidate.FilePath)\r
 379                                      let relativeFilePath = localFile.AsRelativeTo(accountInfo.AccountPath)\r
 380                                      where\r
 381                                          !cloudFiles.Any(r => r.RelativeUrlToFilePath(accountInfo.UserName) == relativeFilePath)\r
 382                                      select localFile).ToList();\r
 383 \r
 384 \r
 385 \r
 386                 //Set the status of missing files to Conflict\r
 387                 foreach (var item in filesToDelete)\r
 388                 {\r
 389                     //Try to acquire a gate on the file, to take into account files that have been dequeued\r
 390                     //and are being processed\r
 391                     using (var gate = NetworkGate.Acquire(item.FullName, NetworkOperation.Deleting))\r
 392                     {\r
 393                         if (gate.Failed)\r
 394                             continue;\r
 395                         StatusKeeper.SetFileState(item.FullName, FileStatus.Conflict, FileOverlayStatus.Deleted);\r
 396                     }\r
 397                 }\r
 398                 UpdateStatus(PithosStatus.HasConflicts);\r
 399                 StatusNotification.NotifyConflicts(filesToDelete, String.Format("{0} local files are missing from Pithos, possibly because they were deleted", filesToDelete.Count));\r
 400                 StatusNotification.NotifyForFiles(filesToDelete, String.Format("{0} files were deleted", filesToDelete.Count), TraceLevel.Info);\r
 401             }\r
 402             else\r
 403             {\r
 404                 var deletedFiles = new List<FileSystemInfo>();\r
 405                 foreach (var objectInfo in cloudFiles)\r
 406                 {\r
 407                     Log.DebugFormat("Handle deleted [{0}]",objectInfo.Uri);\r
 408                     var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);\r
 409                     var item = FileAgent.GetFileAgent(accountInfo).GetFileSystemInfo(relativePath);\r
 410                     Log.DebugFormat("Will delete [{0}] for [{1}]", item.FullName,objectInfo.Uri);\r
 411                     if (item.Exists)\r
 412                     {\r
 413                         if ((item.Attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)\r
 414                         {\r
 415                             item.Attributes = item.Attributes & ~FileAttributes.ReadOnly;\r
 416 \r
 417                         }\r
 418                         var directory = item as DirectoryInfo;\r
 419                         if (directory!=null)\r
 420                             directory.Delete(true);\r
 421                         else\r
 422                             item.Delete();\r
 423                         Log.DebugFormat("Deleted [{0}] for [{1}]", item.FullName, objectInfo.Uri);\r
 424                         DateTime lastDate;\r
 425                         _lastSeen.TryRemove(item.FullName, out lastDate);\r
 426                         deletedFiles.Add(item);\r
 427                     }\r
 428                     StatusKeeper.SetFileState(item.FullName, FileStatus.Deleted, FileOverlayStatus.Deleted);\r
 429                 }\r
 430                 Log.InfoFormat("[{0}] files were deleted",deletedFiles.Count);\r
 431                 StatusNotification.NotifyForFiles(deletedFiles, String.Format("{0} files were deleted", deletedFiles.Count), TraceLevel.Info);\r
 432             }\r
 433 \r
 434         }\r
 435 \r
 436         /// <summary>\r
 437         /// Creates a Sync action for each changed server file\r
 438         /// </summary>\r
 439         /// <param name="accountInfo"></param>\r
 440         /// <param name="changes"></param>\r
 441         /// <returns></returns>\r
 442         private IEnumerable<CloudAction> ChangesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> changes)\r
 443         {\r
 444             if (changes == null)\r
 445                 throw new ArgumentNullException();\r
 446             Contract.EndContractBlock();\r
 447             var fileAgent = FileAgent.GetFileAgent(accountInfo);\r
 448 \r
 449             //In order to avoid multiple iterations over the files, we iterate only once\r
 450             //over the remote files\r
 451             foreach (var objectInfo in changes)\r
 452             {\r
 453                 var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);\r
 454                 //If a directory object already exists, we may need to sync it\r
 455                 if (fileAgent.Exists(relativePath))\r
 456                 {\r
 457                     var localFile = fileAgent.GetFileSystemInfo(relativePath);\r
 458                     //We don't need to sync directories\r
 459                     if (objectInfo.Content_Type == @"application/directory" && localFile is DirectoryInfo)\r
 460                         continue;\r
 461                     using (new SessionScope(FlushAction.Never))\r
 462                     {\r
 463                         var state = StatusKeeper.GetStateByFilePath(localFile.FullName);\r
 464                         _lastSeen[localFile.FullName] = DateTime.Now;\r
 465                         //Common files should be checked on a per-case basis to detect differences, which is newer\r
 466 \r
 467                         yield return new CloudAction(accountInfo, CloudActionType.MustSynch,\r
 468                                                      localFile, objectInfo, state, accountInfo.BlockSize,\r
 469                                                      accountInfo.BlockHash);\r
 470                     }\r
 471                 }\r
 472                 else\r
 473                 {\r
 474                     //Remote files should be downloaded\r
 475                     yield return new CloudDownloadAction(accountInfo, objectInfo);\r
 476                 }\r
 477             }\r
 478         }\r
 479 \r
 480         /// <summary>\r
 481         /// Creates a Local Move action for each moved server file\r
 482         /// </summary>\r
 483         /// <param name="accountInfo"></param>\r
 484         /// <param name="moves"></param>\r
 485         /// <returns></returns>\r
 486         private IEnumerable<CloudAction> MovesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> moves)\r
 487         {\r
 488             if (moves == null)\r
 489                 throw new ArgumentNullException();\r
 490             Contract.EndContractBlock();\r
 491             var fileAgent = FileAgent.GetFileAgent(accountInfo);\r
 492 \r
 493             //In order to avoid multiple iterations over the files, we iterate only once\r
 494             //over the remote files\r
 495             foreach (var objectInfo in moves)\r
 496             {\r
 497                 var previousRelativepath = objectInfo.Previous.RelativeUrlToFilePath(accountInfo.UserName);\r
 498                 //If the previous file already exists, we can execute a Move operation\r
 499                 if (fileAgent.Exists(previousRelativepath))\r
 500                 {\r
 501                     var previousFile = fileAgent.GetFileSystemInfo(previousRelativepath);\r
 502                     using (new SessionScope(FlushAction.Never))\r
 503                     {\r
 504                         var state = StatusKeeper.GetStateByFilePath(previousFile.FullName);\r
 505                         _lastSeen[previousFile.FullName] = DateTime.Now;\r
 506 \r
 507                         //For each moved object we need to move both the local file and update                                                \r
 508                         yield return new CloudAction(accountInfo, CloudActionType.RenameLocal,\r
 509                                                      previousFile, objectInfo, state, accountInfo.BlockSize,\r
 510                                                      accountInfo.BlockHash);\r
 511                         //For modified files, we need to download the changes as well\r
 512                         if (objectInfo.Hash!=objectInfo.PreviousHash)\r
 513                             yield return new CloudDownloadAction(accountInfo,objectInfo);\r
 514                     }\r
 515                 }\r
 516                 //If the previous file does not exist, we need to download it in the new location\r
 517                 else\r
 518                 {\r
 519                     //Remote files should be downloaded\r
 520                     yield return new CloudDownloadAction(accountInfo, objectInfo);\r
 521                 }\r
 522             }\r
 523         }\r
 524 \r
 525 \r
 526         /// <summary>\r
 527         /// Creates a download action for each new server file\r
 528         /// </summary>\r
 529         /// <param name="accountInfo"></param>\r
 530         /// <param name="creates"></param>\r
 531         /// <returns></returns>\r
 532         private IEnumerable<CloudAction> CreatesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> creates)\r
 533         {\r
 534             if (creates == null)\r
 535                 throw new ArgumentNullException();\r
 536             Contract.EndContractBlock();\r
 537             var fileAgent = FileAgent.GetFileAgent(accountInfo);\r
 538 \r
 539             //In order to avoid multiple iterations over the files, we iterate only once\r
 540             //over the remote files\r
 541             foreach (var objectInfo in creates)\r
 542             {\r
 543                 if (Log.IsDebugEnabled)\r
 544                     Log.DebugFormat("[NEW INFO] {0}",objectInfo.Uri);\r
 545 \r
 546                 var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);\r
 547                 //If the object already exists, we probably have a conflict\r
 548                 if (fileAgent.Exists(relativePath))\r
 549                 {\r
 550                     Log.DebugFormat("[SKIP EXISTING] {0}", objectInfo.Uri);\r
 551                     //If a directory object already exists, we don't need to perform any other action                    \r
 552                     var localFile = fileAgent.GetFileSystemInfo(relativePath);\r
 553                     StatusKeeper.SetFileState(localFile.FullName, FileStatus.Conflict, FileOverlayStatus.Conflict);\r
 554                 }\r
 555                 else\r
 556                 {\r
 557                     //Remote files should be downloaded\r
 558                     yield return new CloudDownloadAction(accountInfo, objectInfo);\r
 559                 }\r
 560             }\r
 561         }\r
 562 \r
 563         /// <summary>\r
 564         /// Notify the UI to update the visual status\r
 565         /// </summary>\r
 566         /// <param name="status"></param>\r
 567         private void UpdateStatus(PithosStatus status)\r
 568         {\r
 569             try\r
 570             {\r
 571                 StatusNotification.SetPithosStatus(status);\r
 572                 //StatusNotification.Notify(new Notification());\r
 573             }\r
 574             catch (Exception exc)\r
 575             {\r
 576                 //Failure is not critical, just log it\r
 577                 Log.Warn("Error while updating status", exc);\r
 578             }\r
 579         }\r
 580 \r
 581         private static void CreateContainerFolders(AccountInfo accountInfo, IEnumerable<ContainerInfo> containers)\r
 582         {\r
 583             var containerPaths = from container in containers\r
 584                                  let containerPath = Path.Combine(accountInfo.AccountPath, container.Name)\r
 585                                  where container.Name != FolderConstants.TrashContainer && !Directory.Exists(containerPath)\r
 586                                  select containerPath;\r
 587 \r
 588             foreach (var path in containerPaths)\r
 589             {\r
 590                 Directory.CreateDirectory(path);\r
 591             }\r
 592         }\r
 593 \r
 594         public void SetSyncUris(Uri[] uris)\r
 595         {            \r
 596             SelectiveUris=uris.ToList();\r
 597         }\r
 598 \r
 599         protected List<Uri> SelectiveUris\r
 600         {\r
 601             get { return _selectiveUris;}\r
 602             set { _selectiveUris = value; }\r
 603         }\r
 604 \r
 605         public void AddAccount(AccountInfo accountInfo)\r
 606         {\r
 607             //Avoid adding a duplicate accountInfo\r
 608             _accounts.TryAdd(accountInfo.UserName, accountInfo);\r
 609         }\r
 610 \r
 611         public void RemoveAccount(AccountInfo accountInfo)\r
 612         {\r
 613             AccountInfo account;\r
 614             _accounts.TryRemove(accountInfo.UserName,out account);\r
 615             SnapshotDifferencer differencer;\r
 616             _differencer.Differencers.TryRemove(accountInfo.UserName, out differencer);\r
 617         }\r
 618     }\r
 619 }\r