source: branches/3.3-HiveMigration/sources/HeuristicLab.Hive/HeuristicLab.Hive.Server.Core/3.3/SlaveCommunicator.cs @ 4263

#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2008 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Threading;
using System.Transactions;
using HeuristicLab.Hive.Contracts;
using HeuristicLab.Hive.Contracts.BusinessObjects;
using HeuristicLab.Hive.Contracts.Interfaces;
using HeuristicLab.Hive.Server.Core.InternalInterfaces;
using HeuristicLab.PluginInfrastructure;
using HeuristicLab.Tracing;
using HeuristicLab.Hive.Contracts.ResponseObjects;

namespace HeuristicLab.Hive.Server.Core {
  /// <summary>
  /// The ClientCommunicator manages the whole communication with the client
  /// </summary>
  public class SlaveCommunicator : ISlaveCommunicator,
    IInternalSlaveCommunicator {
    private static Dictionary<Guid, DateTime> lastHeartbeats = new Dictionary<Guid, DateTime>();
    private static Dictionary<Guid, int> newAssignedJobs = new Dictionary<Guid, int>();
    private static Dictionary<Guid, int> pendingJobs = new Dictionary<Guid, int>();

    private static ReaderWriterLockSlim heartbeatLock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);

    //private ISessionFactory factory;
    private ILifecycleManager lifecycleManager;
    private IInternalJobManager jobManager;
    private IScheduler scheduler;

    private static int PENDING_TIMEOUT = 100;

    /// <summary>
    /// Initialization of the Adapters to the database
    /// Initialization of Eventhandler for the lifecycle management
    /// Initialization of lastHearbeats Dictionary
    /// </summary>
    public SlaveCommunicator() {
      //factory = ServiceLocator.GetSessionFactory();

      lifecycleManager = ServiceLocator.GetLifecycleManager();
      jobManager = ServiceLocator.GetJobManager() as IInternalJobManager;
      scheduler = ServiceLocator.GetScheduler();

      lifecycleManager.RegisterHeartbeat(new EventHandler(lifecycleManager_OnServerHeartbeat));
    }

    /// <summary>
    /// Check if online clients send their hearbeats
    /// if not -> set them offline and check if they where calculating a job
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    void lifecycleManager_OnServerHeartbeat(object sender, EventArgs e) {
      Logger.Debug("Server Heartbeat ticked");

      // [chn] why is transaction management done here
      using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required, new TransactionOptions { IsolationLevel = ApplicationConstants.ISOLATION_LEVEL_SCOPE })) {
        List<ClientDto> allClients = new List<ClientDto>(DaoLocator.ClientDao.FindAll());

        foreach (ClientDto client in allClients) {
          if (client.State != State.Offline && client.State != State.NullState) {
            heartbeatLock.EnterUpgradeableReadLock();

            if (!lastHeartbeats.ContainsKey(client.Id)) {
              Logger.Info("Client " + client.Id +
                              " wasn't offline but hasn't sent heartbeats - setting offline");
              client.State = State.Offline;
              DaoLocator.ClientDao.Update(client);
              Logger.Info("Client " + client.Id +
                              " wasn't offline but hasn't sent heartbeats - Resetting all his jobs");
              foreach (JobDto job in DaoLocator.JobDao.FindActiveJobsOfSlave(client)) {
                //maybe implementa n additional Watchdog? Till then, just set them offline..
                DaoLocator.JobDao.SetJobOffline(job);
              }
            } else {
              DateTime lastHbOfClient = lastHeartbeats[client.Id];

              TimeSpan dif = DateTime.Now.Subtract(lastHbOfClient);
              // check if time between last hearbeat and now is greather than HEARTBEAT_MAX_DIF
              if (dif.TotalSeconds > ApplicationConstants.HEARTBEAT_MAX_DIF) {
                // if client calculated jobs, the job must be reset
                Logger.Info("Client timed out and is on RESET");
                foreach (JobDto job in DaoLocator.JobDao.FindActiveJobsOfSlave(client)) {
                  DaoLocator.JobDao.SetJobOffline(job);
                  lock (newAssignedJobs) {
                    if (newAssignedJobs.ContainsKey(job.Id))
                      newAssignedJobs.Remove(job.Id);
                  }
                }
                Logger.Debug("setting client offline");
                // client must be set offline
                client.State = State.Offline;

                //clientAdapter.Update(client);
                DaoLocator.ClientDao.Update(client);

                Logger.Debug("removing it from the heartbeats list");
                heartbeatLock.EnterWriteLock();
                lastHeartbeats.Remove(client.Id);
                heartbeatLock.ExitWriteLock();
              }
            }

            heartbeatLock.ExitUpgradeableReadLock();
          } else {
            //TODO: RLY neccesary?
            //HiveLogger.Info(this.ToString() + ": Client " + client.Id + " has wrong state: Shouldn't have offline or nullstate, has " + client.State);
            heartbeatLock.EnterWriteLock();
            //HiveLogger.Info(this.ToString() + ": Client " + client.Id + " has wrong state: Resetting all his jobs");
            if (lastHeartbeats.ContainsKey(client.Id))
              lastHeartbeats.Remove(client.Id);
            foreach (JobDto job in DaoLocator.JobDao.FindActiveJobsOfSlave(client)) {
              DaoLocator.JobDao.SetJobOffline(job);
            }
            heartbeatLock.ExitWriteLock();
          }
        }
        CheckForPendingJobs();
        //        DaoLocator.DestroyContext();
        scope.Complete();
      }
    }

    private void CheckForPendingJobs() {
      IList<JobDto> pendingJobsInDB = new List<JobDto>(DaoLocator.JobDao.GetJobsByState(State.Pending));

      foreach (JobDto currJob in pendingJobsInDB) {
        lock (pendingJobs) {
          if (pendingJobs.ContainsKey(currJob.Id)) {
            if (pendingJobs[currJob.Id] <= 0) {
              currJob.State = State.Offline;
              DaoLocator.JobDao.Update(currJob);
            } else {
              pendingJobs[currJob.Id]--;
            }
          }
        }
      }
    }

    #region IClientCommunicator Members

    /// <summary>
    /// Login process for the client
    /// A hearbeat entry is created as well (login is the first hearbeat)
    /// </summary>
    /// <param name="slaveInfo"></param>
    /// <returns></returns>
    public Response Login(ClientDto slaveInfo) {
      Response response = new Response();

      heartbeatLock.EnterWriteLock();
      if (lastHeartbeats.ContainsKey(slaveInfo.Id)) {
        lastHeartbeats[slaveInfo.Id] = DateTime.Now;
      } else {
        lastHeartbeats.Add(slaveInfo.Id, DateTime.Now);
      }
      heartbeatLock.ExitWriteLock();

      ClientDto dbClient = DaoLocator.ClientDao.FindById(slaveInfo.Id);

      //Really set offline? 
      //Reconnect issues with the currently calculating jobs
      slaveInfo.State = State.Idle;
      slaveInfo.CalendarSyncStatus = dbClient != null ? dbClient.CalendarSyncStatus : CalendarState.NotAllowedToFetch;

      if (dbClient == null)
        DaoLocator.ClientDao.Insert(slaveInfo);
      else
        DaoLocator.ClientDao.Update(slaveInfo);

      return response;
    }

    public ResponseCalendar GetCalendar(Guid clientId) {
      ResponseCalendar response = new ResponseCalendar();

      ClientDto client = DaoLocator.ClientDao.FindById(clientId);
      if (client == null) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.GetCalendar_ResourceNotFound;
        return response;
      }

      response.ForceFetch = (client.CalendarSyncStatus == CalendarState.ForceFetch);

      IEnumerable<AppointmentDto> appointments = DaoLocator.UptimeCalendarDao.GetCalendarForClient(client);
      if (appointments.Count() == 0) {
        response.StatusMessage = ResponseStatus.GetCalendar_NoCalendarFound;
        //response.Success = false;
      } else {
        //response.Success = true;
        response.Appointments = appointments;
      }

      client.CalendarSyncStatus = CalendarState.Fetched;
      DaoLocator.ClientDao.Update(client);
      return response;
    }

    public Response SetCalendarStatus(Guid clientId, CalendarState state) {
      Response response = new Response();
      ClientDto client = DaoLocator.ClientDao.FindById(clientId);
      if (client == null) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.GetCalendar_ResourceNotFound;
        return response;
      }

      client.CalendarSyncStatus = state;
      DaoLocator.ClientDao.Update(client);

      return response;
    }

    /// <summary>
    /// The client has to send regulary heartbeats
    /// this hearbeats will be stored in the heartbeats dictionary
    /// check if there is work for the client and send the client a response if he should pull a job
    /// </summary>
    /// <param name="hbData"></param>
    /// <returns></returns>
    public ResponseHeartBeat ProcessHeartBeat(HeartBeatData hbData) {
      Logger.Debug("BEGIN Processing Heartbeat for Client " + hbData.SlaveId);

      ResponseHeartBeat response = new ResponseHeartBeat();
      response.ActionRequest = new List<MessageContainer>();

      Logger.Debug("BEGIN Started Client Fetching");
      ClientDto client = DaoLocator.ClientDao.FindById(hbData.SlaveId);
      Logger.Debug("END Finished Client Fetching");
      // check if the client is logged in
      if (client.State == State.Offline || client.State == State.NullState) {
        // response.Success = false;
        response.StatusMessage = ResponseStatus.ProcessHeartBeat_UserNotLoggedIn;
        response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.NoMessage));

        Logger.Error("ProcessHeartBeat: Client state null or offline: " + client);

        return response;
      }

      client.NrOfFreeCores = hbData.FreeCores;
      client.FreeMemory = hbData.FreeMemory;

      // save timestamp of this heartbeat
      Logger.Debug("BEGIN Locking for Heartbeats");
      heartbeatLock.EnterWriteLock();
      Logger.Debug("END Locked for Heartbeats");
      if (lastHeartbeats.ContainsKey(hbData.SlaveId)) {
        lastHeartbeats[hbData.SlaveId] = DateTime.Now;
      } else {
        lastHeartbeats.Add(hbData.SlaveId, DateTime.Now);
      }
      heartbeatLock.ExitWriteLock();

      Logger.Debug("BEGIN Processing Heartbeat Jobs");
      ProcessJobProcess(hbData, response);
      Logger.Debug("END Processed Heartbeat Jobs");

      //check if new Cal must be loaded
      if (client.CalendarSyncStatus == CalendarState.Fetch || client.CalendarSyncStatus == CalendarState.ForceFetch) {
        response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.FetchOrForceFetchCalendar));

        //client.CalendarSyncStatus = CalendarState.Fetching;

        Logger.Info("fetch or forcefetch sent");
      }

      // check if client has a free core for a new job
      // if true, ask scheduler for a new job for this client
      Logger.Debug(" BEGIN Looking for Client Jobs");
      if (hbData.FreeCores > 0 && scheduler.ExistsJobForSlave(hbData)) {
        response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.FetchJob));
      } else {
        response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.NoMessage));
      }
      Logger.Debug(" END Looked for Client Jobs");

      DaoLocator.ClientDao.Update(client);

      //tx.Commit();
      Logger.Debug(" END Processed Heartbeat for Client " + hbData.SlaveId);
      return response;
    }

    /// <summary>
    /// Process the Job progress sent by a client
    /// [chn] this method needs to be refactored, because its a performance hog
    /// 
    /// what it does:
    /// (1) find out if the jobs that should be calculated by this client (from db) and compare if they are consistent with what the joblist the client sent
    /// (2) find out if every job from the joblist really should be calculated by this client
    /// (3) checks if a job should be aborted and issues Message
    /// (4) update job-progress and write to db
    /// (5) if snapshot is requested, issue Message
    /// 
    /// (6) for each job from DB, check if there is a job from client (again).
    /// (7) if job matches, it is removed from newAssigneJobs
    /// (8) if job !matches, job's TTL is reduced by 1, 
    /// (9) if TTL==0, job is set to Abort (save to DB), and Message to Abort job is issued to client
    /// 
    /// 
    /// 
    /// quirks:
    /// (1) the response-object is modified during the foreach-loop (only last element counts)
    /// (2) state Abort results in Finished. This should be: AbortRequested, Aborted.
    /// </summary>
    /// <param name="hbData"></param>
    /// <param name="jobAdapter"></param>
    /// <param name="clientAdapter"></param>
    /// <param name="response"></param>
    private void ProcessJobProcess(HeartBeatData hbData, ResponseHeartBeat response) {
      Logger.Debug("Started for Client " + hbData.SlaveId);
      List<JobDto> jobsOfClient = new List<JobDto>(DaoLocator.JobDao.FindActiveJobsOfSlave(DaoLocator.ClientDao.FindById(hbData.SlaveId)));
      if (hbData.JobProgress != null && hbData.JobProgress.Count > 0) {
        if (jobsOfClient == null || jobsOfClient.Count == 0) {
          //response.Success = false;
          //response.StatusMessage = ApplicationConstants.RESPONSE_COMMUNICATOR_JOB_IS_NOT_BEEING_CALCULATED;

          foreach (Guid jobId in hbData.JobProgress.Keys) {
            response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.AbortJob, jobId));
          }

          Logger.Error("There is no job calculated by this user " + hbData.SlaveId + ", advise him to abort all");
          return;
        }

        foreach (KeyValuePair<Guid, double> jobProgress in hbData.JobProgress) {
          JobDto curJob = DaoLocator.JobDao.FindById(jobProgress.Key);
          curJob.Client = DaoLocator.ClientDao.GetClientForJob(curJob.Id);
          if (curJob.Client == null || curJob.Client.Id != hbData.SlaveId) {
            //response.Success = false;
            //response.StatusMessage = ApplicationConstants.RESPONSE_COMMUNICATOR_JOB_IS_NOT_BEEING_CALCULATED;
            response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.AbortJob, curJob.Id));
            Logger.Error("There is no job calculated by this user " + hbData.SlaveId + " Job: " + curJob);
          } else if (curJob.State == State.Abort) {
            // a request to abort the job has been set
            response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.AbortJob, curJob.Id));
            curJob.State = State.Finished;
          } else {
            // save job progress
            curJob.Percentage = jobProgress.Value;

            if (curJob.State == State.RequestSnapshot) {
              // a request for a snapshot has been set
              response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.RequestSnapshot, curJob.Id));
              curJob.State = State.RequestSnapshotSent;
            }
          }
          DaoLocator.JobDao.Update(curJob);
        }
      }
      foreach (JobDto currJob in jobsOfClient) {
        bool found = false;
        if (hbData.JobProgress != null) {
          foreach (Guid jobId in hbData.JobProgress.Keys) {
            if (jobId == currJob.Id) {
              found = true;
              break;
            }
          }
        }
        if (!found) {
          lock (newAssignedJobs) {
            if (newAssignedJobs.ContainsKey(currJob.Id)) {
              newAssignedJobs[currJob.Id]--;
              Logger.Error("Job TTL Reduced by one for job: " + currJob + "and is now: " + newAssignedJobs[currJob.Id] + ". User that sucks: " + currJob.Client);
              if (newAssignedJobs[currJob.Id] <= 0) {
                Logger.Error("Job TTL reached Zero, Job gets removed: " + currJob + " and set back to offline. User that sucks: " + currJob.Client);

                currJob.State = State.Offline;
                DaoLocator.JobDao.Update(currJob);

                response.ActionRequest.Add(new MessageContainer(MessageContainer.MessageType.AbortJob, currJob.Id));

                newAssignedJobs.Remove(currJob.Id);
              }
            } else {
              Logger.Error("Job ID wasn't with the heartbeats:  " + currJob);
              currJob.State = State.Offline;
              DaoLocator.JobDao.Update(currJob);
            }
          } // lock
        } else {
          lock (newAssignedJobs) {

            if (newAssignedJobs.ContainsKey(currJob.Id)) {
              Logger.Info("Job is sending a heart beat, removing it from the newAssignedJobList: " + currJob);
              newAssignedJobs.Remove(currJob.Id);
            }
          }
        }
      }
    }

    /// <summary>
    /// if the client was told to pull a job he calls this method
    /// the server selects a job and sends it to the client
    /// </summary>
    /// <param name="clientId"></param>
    /// <returns></returns>
    public ResponseObject<JobDto> GetJob(Guid clientId) {
      ResponseObject<JobDto> response = new ResponseObject<JobDto>();

      JobDto job2Calculate = scheduler.GetNextJobForSlave(clientId);
      if (job2Calculate != null) {
        response.Obj = job2Calculate;
        response.Obj.PluginsNeeded = DaoLocator.PluginInfoDao.GetPluginDependenciesForJob(response.Obj);

        Logger.Info("Job pulled: " + job2Calculate + " for user " + clientId);
        lock (newAssignedJobs) {
          if (!newAssignedJobs.ContainsKey(job2Calculate.Id))
            newAssignedJobs.Add(job2Calculate.Id, ApplicationConstants.JOB_TIME_TO_LIVE);
        }
      } else {
        //response.Success = false;
        response.Obj = null;
        response.StatusMessage = ResponseStatus.GetJob_NoJobsAvailable;
        Logger.Info("No more Jobs left for " + clientId);
      }
      return response;
    }

    public ResponseResultReceived ProcessJobResult(Stream stream, bool finished) {
      Logger.Info("BEGIN Job received for Storage - main method:");

      //Stream jobResultStream = null;
      //Stream jobStream = null;

      //try {
      BinaryFormatter formatter = new BinaryFormatter();

      JobResult result = (JobResult)formatter.Deserialize(stream);

      //important - repeatable read isolation level is required here, 
      //otherwise race conditions could occur when writing the stream into the DB
      //just removed TransactionIsolationLevel.RepeatableRead
      //tx = session.BeginTransaction();

      ResponseResultReceived response = ProcessJobResult(result.ClientId, result.JobId, new byte[] { }, result.Percentage, result.Exception, finished);

      if (response.StatusMessage == ResponseStatus.Ok) {
        Logger.Debug("Trying to aquire WCF Job Stream");
        //jobStream = DaoLocator.JobDao.GetSerializedJobStream(result.JobId);
        //Logger.Debug("Job Stream Aquired");
        byte[] buffer = new byte[3024];
        List<byte> serializedJob = new List<byte>();
        int read = 0;
        int i = 0;
        while ((read = stream.Read(buffer, 0, buffer.Length)) > 0) {
          for (int j = 0; j < read; j++) {
            serializedJob.Add(buffer[j]);
          }
          if (i % 100 == 0)
            Logger.Debug("Writing to stream: " + i);
          //jobStream.Write(buffer, 0, read);
          i++;
        }
        Logger.Debug("Done Writing, closing the stream!");
        //jobStream.Close();

        DaoLocator.JobDao.SetBinaryJobFile(result.JobId, serializedJob.ToArray());
      }
      Logger.Info("END Job received for Storage:");
      stream.Dispose();
      return response;
    }

    private ResponseResultReceived ProcessJobResult(Guid clientId, Guid jobId, byte[] result, double? percentage, string exception, bool finished) {
      Logger.Info("BEGIN Job received for Storage - SUB method: " + jobId);

      ResponseResultReceived response = new ResponseResultReceived();
      ClientDto client = DaoLocator.ClientDao.FindById(clientId);

      SerializedJob job = new SerializedJob();

      if (job != null) {
        job.JobInfo = DaoLocator.JobDao.FindById(jobId);
        if (job.JobInfo != null) {
          job.JobInfo.Client = job.JobInfo.Client = DaoLocator.ClientDao.GetClientForJob(jobId);
        }
      }

      if (job != null && job.JobInfo == null) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.ProcessJobResult_JobDoesNotExist;
        response.JobId = jobId;
        Logger.Error("No job with Id " + jobId);

        //tx.Rollback();
        return response;
      }
      if (job.JobInfo.State == State.Abort) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.ProcessJobResult_JobAborted;

        Logger.Error("Job was aborted! " + job.JobInfo);

        //tx.Rollback();
        return response;
      }
      if (job.JobInfo.Client == null) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.ProcessJobResult_JobIsNotBeeingCalculated;
        response.JobId = jobId;

        Logger.Error("Job is not being calculated (client = null)! " + job.JobInfo);

        //tx.Rollback();
        return response;
      }
      if (job.JobInfo.Client.Id != clientId) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.ProcessJobResult_WrongClientForJob;
        response.JobId = jobId;

        Logger.Error("Wrong Client for this Job! " + job.JobInfo + ", Sending Client is: " + clientId);

        //tx.Rollback();
        return response;
      }
      if (job.JobInfo.State == State.Finished) {
        response.StatusMessage = ResponseStatus.Ok;
        response.JobId = jobId;

        Logger.Error("Job already finished! " + job.JobInfo + ", Sending Client is: " + clientId);

        //tx.Rollback();
        return response;
      }
      //Todo: RequestsnapshotSent => calculating?
      if (job.JobInfo.State == State.RequestSnapshotSent) {
        job.JobInfo.State = State.Calculating;
      }
      if (job.JobInfo.State != State.Calculating && job.JobInfo.State != State.Pending) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.ProcessJobResult_InvalidJobState;
        response.JobId = jobId;

        Logger.Error("Wrong Job State, job is: " + job.JobInfo);

        //tx.Rollback();
        return response;
      }
      job.JobInfo.Percentage = percentage;

      if (!string.IsNullOrEmpty(exception)) {
        job.JobInfo.State = State.Failed;
        job.JobInfo.Exception = exception;
        job.JobInfo.DateFinished = DateTime.Now;
      } else if (finished) {
        job.JobInfo.State = State.Finished;
        job.JobInfo.DateFinished = DateTime.Now;
      }

      job.SerializedJobData = result;

      DaoLocator.JobDao.Update(job.JobInfo);

      response.StatusMessage = ResponseStatus.Ok;
      response.JobId = jobId;
      response.Finished = finished;

      Logger.Info("END Job received for Storage - SUB method: " + jobId);
      return response;

    }

    /// <summary>
    /// the client can send job results during calculating 
    /// and will send a final job result when he finished calculating
    /// these job results will be stored in the database
    /// </summary>
    /// <param name="clientId"></param>
    /// <param name="jobId"></param>
    /// <param name="result"></param>
    /// <param name="exception"></param>
    /// <param name="finished"></param>
    /// <returns></returns>
    public ResponseResultReceived StoreFinishedJobResult(Guid clientId,
      Guid jobId,
      byte[] result,
      double percentage,
      string exception) {

      return ProcessJobResult(clientId, jobId, result, percentage, exception, true);
    }

    public ResponseResultReceived ProcessSnapshot(Guid clientId, Guid jobId, byte[] result, double percentage, string exception) {
      return ProcessJobResult(clientId, jobId, result, percentage, exception, false);
    }

    /// <summary>
    /// when a client logs out the state will be set
    /// and the entry in the last hearbeats dictionary will be removed
    /// </summary>
    /// <param name="clientId"></param>
    /// <returns></returns>                       
    public Response Logout(Guid clientId) {
      Logger.Info("Client logged out " + clientId);

      Response response = new Response();

      heartbeatLock.EnterWriteLock();
      if (lastHeartbeats.ContainsKey(clientId))
        lastHeartbeats.Remove(clientId);
      heartbeatLock.ExitWriteLock();

      ClientDto client = DaoLocator.ClientDao.FindById(clientId);
      if (client == null) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.Logout_SlaveNotRegistered;
        return response;
      }
      if (client.State == State.Calculating) {
        // check wich job the client was calculating and reset it
        IEnumerable<JobDto> jobsOfClient = DaoLocator.JobDao.FindActiveJobsOfSlave(client);
        foreach (JobDto job in jobsOfClient) {
          if (job.State != State.Finished)
            DaoLocator.JobDao.SetJobOffline(job);
        }
      }

      client.State = State.Offline;
      DaoLocator.ClientDao.Update(client);

      return response;
    }

    /// <summary>
    /// If a client goes offline and restores a job he was calculating 
    /// he can ask the client if he still needs the job result
    /// </summary>
    /// <param name="jobId"></param>
    /// <returns></returns>
    public Response IsJobStillNeeded(Guid jobId) {
      Response response = new Response();
      JobDto job = DaoLocator.JobDao.FindById(jobId);
      if (job == null) {
        //response.Success = false;
        response.StatusMessage = ResponseStatus.IsJobStillNeeded_JobDoesNotExist;
        Logger.Error("Job doesn't exist (anymore)! " + jobId);
        return response;
      }
      if (job.State == State.Finished) {
        //response.Success = true;
        response.StatusMessage = ResponseStatus.IsJobStillNeeded_JobAlreadyFinished;
        Logger.Error("already finished! " + job);
        return response;
      }
      job.State = State.Pending;
      lock (pendingJobs) {
        pendingJobs.Add(job.Id, PENDING_TIMEOUT);
      }

      DaoLocator.JobDao.Update(job);

      return response;
    }

    public ResponseList<CachedHivePluginInfoDto> GetPlugins(List<HivePluginInfoDto> pluginList) {
      ResponseList<CachedHivePluginInfoDto> response = new ResponseList<CachedHivePluginInfoDto>();
      response.List = new List<CachedHivePluginInfoDto>();
      foreach (HivePluginInfoDto pluginInfo in pluginList) {
        if (pluginInfo.Update) {
          //check if there is a newer version         
          IPluginDescription ipd = ApplicationManager.Manager.Plugins.Where(pd => pd.Name == pluginInfo.Name && pd.Version.Major == pluginInfo.Version.Major && pd.Version.Minor == pluginInfo.Version.Minor && pd.Version.Revision > pluginInfo.Version.Revision).SingleOrDefault();
          if (ipd != null) {
            response.List.Add(ConvertPluginDescriptorToDto(ipd));
          }
        } else {
          IPluginDescription ipd = ApplicationManager.Manager.Plugins.Where(pd => pd.Name == pluginInfo.Name && pd.Version.Major == pluginInfo.Version.Major && pd.Version.Minor == pluginInfo.Version.Minor && pd.Version.Revision >= pluginInfo.Version.Revision).SingleOrDefault();
          if (ipd != null) {
            response.List.Add(ConvertPluginDescriptorToDto(ipd));
          } else {
            //response.Success = false;
            response.StatusMessage = ResponseStatus.GetPlugins_PluginsNotAvailable;
            return response;
          }
        }
      }
      return response;
    }

    private CachedHivePluginInfoDto ConvertPluginDescriptorToDto(IPluginDescription currPlugin) {
      CachedHivePluginInfoDto currCachedPlugin = new CachedHivePluginInfoDto {
        Name = currPlugin.Name,
        Version = currPlugin.Version
      };

      foreach (string fileName in from file in currPlugin.Files select file.Name) {
        currCachedPlugin.PluginFiles.Add(new HivePluginFile(File.ReadAllBytes(fileName), fileName));
      }
      return currCachedPlugin;
    }

    #endregion
  }
}