Synnefo » Pithos MS Client

#region

/* -----------------------------------------------------------------------

 * <copyright file="PollAgent.cs" company="GRNet">

 * 

 * Copyright 2011-2012 GRNET S.A. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or

 * without modification, are permitted provided that the following

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 *      copyright notice, this list of conditions and the following

 *      disclaimer.

 *

 *   2. Redistributions in binary form must reproduce the above

 *      copyright notice, this list of conditions and the following

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 *

 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``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 GRNET S.A OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

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 * -----------------------------------------------------------------------

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#endregion

using System.Collections.Concurrent;

using System.ComponentModel.Composition;

using System.Diagnostics;

using System.Diagnostics.Contracts;

using System.IO;

using System.Threading;

using System.Threading.Tasks;

using System.Threading.Tasks.Dataflow;

using Castle.ActiveRecord;

using Pithos.Interfaces;

using Pithos.Network;

using log4net;

namespace Pithos.Core.Agents

{

    using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Text;

    /// <summary>

    /// PollAgent periodically polls the server to detect object changes. The agent retrieves a listing of all

    /// objects and compares it with a previously cached version to detect differences. 

    /// New files are downloaded, missing files are deleted from the local file system and common files are compared

    /// to determine the appropriate action

    /// </summary>

    [Export]

    public class PollAgent

    {

        private static readonly ILog Log = LogManager.GetLogger("PollAgent");

        [System.ComponentModel.Composition.Import]

        public IStatusKeeper StatusKeeper { get; set; }

        [System.ComponentModel.Composition.Import]

        public IPithosSettings Settings { get; set; }

        [System.ComponentModel.Composition.Import]

        public NetworkAgent NetworkAgent { get; set; }

        public IStatusNotification StatusNotification { get; set; }

        private bool _firstPoll = true;

        //The Sync Event signals a manual synchronisation

        private readonly AsyncManualResetEvent _syncEvent = new AsyncManualResetEvent();

        private ConcurrentDictionary<string, DateTime> _lastSeen = new ConcurrentDictionary<string, DateTime>();

        private readonly ConcurrentBag<AccountInfo> _accounts = new ConcurrentBag<AccountInfo>();

        /// <summary>

        /// Start a manual synchronization

        /// </summary>

        public void SynchNow()

        {            

            _syncEvent.Set();

        }

        /// <summary>

        /// Remote files are polled periodically. Any changes are processed

        /// </summary>

        /// <param name="since"></param>

        /// <returns></returns>

        public async Task PollRemoteFiles(DateTime? since = null)

        {

            Debug.Assert(Thread.CurrentThread.IsBackground, "Polling Ended up in the main thread!");

            UpdateStatus(PithosStatus.Syncing);

            StatusNotification.Notify(new PollNotification());

            using (log4net.ThreadContext.Stacks["Retrieve Remote"].Push("All accounts"))

            {

                //If this poll fails, we will retry with the same since value

                var nextSince = since;

                try

                {

                    //Next time we will check for all changes since the current check minus 1 second

                    //This is done to ensure there are no discrepancies due to clock differences

                    var current = DateTime.Now.AddSeconds(-1);

                    var tasks = from accountInfo in _accounts

                                select ProcessAccountFiles(accountInfo, since);

                    await TaskEx.WhenAll(tasks.ToList());

                    _firstPoll = false;

                    //Reschedule the poll with the current timestamp as a "since" value

                    nextSince = current;

                }

                catch (Exception ex)

                {

                    Log.ErrorFormat("Error while processing accounts\r\n{0}", ex);

                    //In case of failure retry with the same "since" value

                }

                UpdateStatus(PithosStatus.InSynch);

                //The multiple try blocks are required because we can't have an await call

                //inside a finally block

                //TODO: Find a more elegant solution for reschedulling in the event of an exception

                try

                {

                    //Wait for the polling interval to pass or the Sync event to be signalled

                    nextSince = await WaitForScheduledOrManualPoll(nextSince);

                }

                finally

                {

                    //Ensure polling is scheduled even in case of error

                    TaskEx.Run(() => PollRemoteFiles(nextSince));                        

                }

            }

        }

        /// <summary>

        /// Wait for the polling period to expire or a manual sync request

        /// </summary>

        /// <param name="since"></param>

        /// <returns></returns>

        private async Task<DateTime?> WaitForScheduledOrManualPoll(DateTime? since)

        {

            var sync = _syncEvent.WaitAsync();

            var wait = TaskEx.Delay(TimeSpan.FromSeconds(Settings.PollingInterval), NetworkAgent.CancellationToken);

            var signaledTask = await TaskEx.WhenAny(sync, wait);

            //Wait for network processing to finish before polling

            var pauseTask=NetworkAgent.ProceedEvent.WaitAsync();

            await TaskEx.WhenAll(signaledTask, pauseTask);

            //If polling is signalled by SynchNow, ignore the since tag

            if (sync.IsCompleted)

            {

                //TODO: Must convert to AutoReset

                _syncEvent.Reset();

                return null;

            }

            return since;

        }

        public async Task ProcessAccountFiles(AccountInfo accountInfo, DateTime? since = null)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))

                throw new ArgumentException("The AccountInfo.AccountPath is empty", "accountInfo");

            Contract.EndContractBlock();

            using (log4net.ThreadContext.Stacks["Retrieve Remote"].Push(accountInfo.UserName))

            {

                await NetworkAgent.GetDeleteAwaiter();

                Log.Info("Scheduled");

                var client = new CloudFilesClient(accountInfo);

                //We don't need to check the trash container

                var containers = client.ListContainers(accountInfo.UserName).Where(c=>c.Name!="trash");

                CreateContainerFolders(accountInfo, containers);

                try

                {

                    //Wait for any deletions to finish

                    await NetworkAgent.GetDeleteAwaiter();

                    //Get the poll time now. We may miss some deletions but it's better to keep a file that was deleted

                    //than delete a file that was created while we were executing the poll                    

                    var pollTime = DateTime.Now;

                    //Get the list of server objects changed since the last check

                    //The name of the container is passed as state in order to create a dictionary of tasks in a subsequent step

                    var listObjects = (from container in containers

                                       select Task<IList<ObjectInfo>>.Factory.StartNew(_ =>

                                             client.ListObjects(accountInfo.UserName, container.Name, since), container.Name)).ToList();

                    //BUG: Can't detect difference between no changes or no objects

                    //ListObjects returns nothing if there are no changes since the last check time (since value)                    

                    //TODO: Must detect the difference between no server objects and no change

                    //NOTE: One option is to "mark" all result lists with their container name, or 

                    //rather the url of the container

                    //Another option 

                    var listShared = Task<IList<ObjectInfo>>.Factory.StartNew(_ => 

                        client.ListSharedObjects(since), "shared");

                    listObjects.Add(listShared);

                    var listTasks = await Task.Factory.WhenAll(listObjects.ToArray());

                    using (log4net.ThreadContext.Stacks["SCHEDULE"].Push("Process Results"))

                    {

                        var dict = listTasks.ToDictionary(t => t.AsyncState);

                        //Get all non-trash objects. Remember, the container name is stored in AsyncState

                        var remoteObjects = from objectList in listTasks

                                            where (string)objectList.AsyncState != "trash"

                                            from obj in objectList.Result

                                            select obj;

                        var sharedObjects = dict["shared"].Result;

                        //DON'T process trashed files

                        //If some files are deleted and added again to a folder, they will be deleted

                        //even though they are new.

                        //We would have to check file dates and hashes to ensure that a trashed file

                        //can be deleted safely from the local hard drive.

                        /*

                        //Items with the same name, hash may be both in the container and the trash

                        //Don't delete items that exist in the container

                        var realTrash = from trash in trashObjects

                                        where

                                            !remoteObjects.Any(

                                                info => info.Name == trash.Name && info.Hash == trash.Hash)

                                        select trash;

                        ProcessTrashedFiles(accountInfo, realTrash);

*/

                        var cleanRemotes = (from info in remoteObjects.Union(sharedObjects)

                                            let name = info.Name

                                            where !name.EndsWith(".ignore", StringComparison.InvariantCultureIgnoreCase) &&

                                                  !name.StartsWith(FolderConstants.CacheFolder + "/",

                                                                   StringComparison.InvariantCultureIgnoreCase)

                                            select info).ToList();

                        var differencer = _differencer.PostSnapshot(accountInfo, cleanRemotes);

                        ProcessDeletedFiles(accountInfo, differencer.Deleted.FilterDirectlyBelow(SelectiveUris), pollTime);

                        // @@@ NEED To add previous state here as well, To compare with previous hash

                        //Create a list of actions from the remote files

                        var allActions = ChangesToActions(accountInfo, differencer.Changed.FilterDirectlyBelow(SelectiveUris))

                                        .Union(

                                        CreatesToActions(accountInfo, differencer.Created.FilterDirectlyBelow(SelectiveUris)));

                        //And remove those that are already being processed by the agent

                        var distinctActions = allActions

                            .Except(NetworkAgent.GetEnumerable(), new PithosMonitor.LocalFileComparer())

                            .ToList();

                        //Queue all the actions

                        foreach (var message in distinctActions)

                        {

                            NetworkAgent.Post(message);

                        }

                        Log.Info("[LISTENER] End Processing");

                    }

                }

                catch (Exception ex)

                {

                    Log.ErrorFormat("[FAIL] ListObjects for{0} in ProcessRemoteFiles with {1}", accountInfo.UserName, ex);

                    return;

                }

                Log.Info("[LISTENER] Finished");

            }

        }

        AccountsDifferencer _differencer = new AccountsDifferencer();

        private List<Uri> _selectiveUris=new List<Uri>();

        /// <summary>

        /// Deletes local files that are not found in the list of cloud files

        /// </summary>

        /// <param name="accountInfo"></param>

        /// <param name="cloudFiles"></param>

        /// <param name="pollTime"></param>

        private void ProcessDeletedFiles(AccountInfo accountInfo, IEnumerable<ObjectInfo> cloudFiles, DateTime pollTime)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))

                throw new ArgumentException("The AccountInfo.AccountPath is empty", "accountInfo");

            if (cloudFiles == null)

                throw new ArgumentNullException("cloudFiles");

            Contract.EndContractBlock();

            //On the first run

            if (_firstPoll)

            {

                //Only consider files that are not being modified, ie they are in the Unchanged state            

                var deleteCandidates = FileState.Queryable.Where(state =>

                    state.FilePath.StartsWith(accountInfo.AccountPath)

                    && state.FileStatus == FileStatus.Unchanged).ToList();

                //TODO: filesToDelete must take into account the Others container            

                var filesToDelete = (from deleteCandidate in deleteCandidates

                                     let localFile = FileInfoExtensions.FromPath(deleteCandidate.FilePath)

                                     let relativeFilePath = localFile.AsRelativeTo(accountInfo.AccountPath)

                                     where

                                         !cloudFiles.Any(r => r.RelativeUrlToFilePath(accountInfo.UserName) == relativeFilePath)

                                     select localFile).ToList();

                //Set the status of missing files to Conflict

                foreach (var item in filesToDelete)

                {

                    //Try to acquire a gate on the file, to take into account files that have been dequeued

                    //and are being processed

                    using (var gate = NetworkGate.Acquire(item.FullName, NetworkOperation.Deleting))

                    {

                        if (gate.Failed)

                            continue;

                        StatusKeeper.SetFileState(item.FullName, FileStatus.Conflict, FileOverlayStatus.Deleted);

                    }

                }

                UpdateStatus(PithosStatus.HasConflicts);

                StatusNotification.NotifyConflicts(filesToDelete, String.Format("{0} local files are missing from Pithos, possibly because they were deleted", filesToDelete.Count));

                StatusNotification.NotifyForFiles(filesToDelete, String.Format("{0} files were deleted", filesToDelete.Count), TraceLevel.Info);

            }

            else

            {

                var deletedFiles = new List<FileSystemInfo>();

                foreach (var objectInfo in cloudFiles)

                {

                    var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);

                    var item = FileAgent.GetFileAgent(accountInfo).GetFileSystemInfo(relativePath);

                    if (item.Exists)

                    {

                        if ((item.Attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)

                        {

                            item.Attributes = item.Attributes & ~FileAttributes.ReadOnly;

                        }

                        item.Delete();

                        DateTime lastDate;

                        _lastSeen.TryRemove(item.FullName, out lastDate);

                        deletedFiles.Add(item);

                    }

                    StatusKeeper.SetFileState(item.FullName, FileStatus.Deleted, FileOverlayStatus.Deleted);

                }

                StatusNotification.NotifyForFiles(deletedFiles, String.Format("{0} files were deleted", deletedFiles.Count), TraceLevel.Info);

            }

        }

        //Creates an appropriate action for each server file

        private IEnumerable<CloudAction> ChangesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> changes)

        {

            if (changes == null)

                throw new ArgumentNullException();

            Contract.EndContractBlock();

            var fileAgent = FileAgent.GetFileAgent(accountInfo);

            //In order to avoid multiple iterations over the files, we iterate only once

            //over the remote files

            foreach (var objectInfo in changes)

            {

                var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);

                //and remove any matching objects from the list, adding them to the commonObjects list

                if (fileAgent.Exists(relativePath))

                {

                    //If a directory object already exists, we don't need to perform any other action                    

                    var localFile = fileAgent.GetFileSystemInfo(relativePath);

                    if (objectInfo.Content_Type == @"application/directory" && localFile is DirectoryInfo)

                        continue;

                    using (new SessionScope(FlushAction.Never))

                    {

                        var state = StatusKeeper.GetStateByFilePath(localFile.FullName);

                        _lastSeen[localFile.FullName] = DateTime.Now;

                        //Common files should be checked on a per-case basis to detect differences, which is newer

                        yield return new CloudAction(accountInfo, CloudActionType.MustSynch,

                                                     localFile, objectInfo, state, accountInfo.BlockSize,

                                                     accountInfo.BlockHash);

                    }

                }

                else

                {

                    //Remote files should be downloaded

                    yield return new CloudDownloadAction(accountInfo, objectInfo);

                }

            }

        }

        private IEnumerable<CloudAction> CreatesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> creates)

        {

            if (creates == null)

                throw new ArgumentNullException();

            Contract.EndContractBlock();

            var fileAgent = FileAgent.GetFileAgent(accountInfo);

            //In order to avoid multiple iterations over the files, we iterate only once

            //over the remote files

            foreach (var objectInfo in creates)

            {

                var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);

                //and remove any matching objects from the list, adding them to the commonObjects list

                if (fileAgent.Exists(relativePath))

                {

                    //If the object already exists, we probably have a conflict

                    //If a directory object already exists, we don't need to perform any other action                    

                    var localFile = fileAgent.GetFileSystemInfo(relativePath);

                    StatusKeeper.SetFileState(localFile.FullName, FileStatus.Conflict, FileOverlayStatus.Conflict);

                }

                else

                {

                    //Remote files should be downloaded

                    yield return new CloudDownloadAction(accountInfo, objectInfo);

                }

            }

        }

        private void ProcessTrashedFiles(AccountInfo accountInfo, IEnumerable<ObjectInfo> trashObjects)

        {

            var fileAgent = FileAgent.GetFileAgent(accountInfo);

            foreach (var trashObject in trashObjects)

            {

                var barePath = trashObject.RelativeUrlToFilePath(accountInfo.UserName);

                //HACK: Assume only the "pithos" container is used. Must find out what happens when

                //deleting a file from a different container

                var relativePath = Path.Combine("pithos", barePath);

                fileAgent.Delete(relativePath);

            }

        }

        /// <summary>

        /// Notify the UI to update the visual status

        /// </summary>

        /// <param name="status"></param>

        private void UpdateStatus(PithosStatus status)

        {

            try

            {

                StatusKeeper.SetPithosStatus(status);

                StatusNotification.Notify(new Notification());

            }

            catch (Exception exc)

            {

                //Failure is not critical, just log it

                Log.Warn("Error while updating status", exc);

            }

        }

        private static void CreateContainerFolders(AccountInfo accountInfo, IEnumerable<ContainerInfo> containers)

        {

            var containerPaths = from container in containers

                                 let containerPath = Path.Combine(accountInfo.AccountPath, container.Name)

                                 where container.Name != FolderConstants.TrashContainer && !Directory.Exists(containerPath)

                                 select containerPath;

            foreach (var path in containerPaths)

            {

                Directory.CreateDirectory(path);

            }

        }

        public void SetSyncUris(Uri[] uris)

        {            

            SelectiveUris=uris.ToList();

        }

        protected List<Uri> SelectiveUris

        {

            get { return _selectiveUris;}

            set { _selectiveUris = value; }

        }

        public void AddAccount(AccountInfo accountInfo)

        {

            if (!_accounts.Contains(accountInfo))

                _accounts.Add(accountInfo);

        }

    }

}