/**
   * @param sesId Session ID.
   * @param taskNodeId Task node ID.
   * @param taskName Task name.
   * @param dep Deployment.
   * @param taskClsName Task class name.
   * @param top Topology.
   * @param startTime Execution start time.
   * @param endTime Execution end time.
   * @param siblings Collection of siblings.
   * @param attrs Map of attributes.
   * @param fullSup {@code True} to enable distributed session attributes and checkpoints.
   * @return New session if one did not exist, or existing one.
   */
  public GridTaskSessionImpl createTaskSession(
      GridUuid sesId,
      UUID taskNodeId,
      String taskName,
      @Nullable GridDeployment dep,
      String taskClsName,
      @Nullable Collection<UUID> top,
      long startTime,
      long endTime,
      Collection<GridComputeJobSibling> siblings,
      Map<Object, Object> attrs,
      boolean fullSup) {
    if (!fullSup) {
      return new GridTaskSessionImpl(
          taskNodeId,
          taskName,
          dep,
          taskClsName,
          sesId,
          top,
          startTime,
          endTime,
          siblings,
          attrs,
          ctx,
          fullSup);
    }

    while (true) {
      GridTaskSessionImpl ses = sesMap.get(sesId);

      if (ses == null) {
        GridTaskSessionImpl old =
            sesMap.putIfAbsent(
                sesId,
                ses =
                    new GridTaskSessionImpl(
                        taskNodeId,
                        taskName,
                        dep,
                        taskClsName,
                        sesId,
                        top,
                        startTime,
                        endTime,
                        siblings,
                        attrs,
                        ctx,
                        fullSup));

        if (old != null) ses = old;
        else
          // Return without acquire.
          return ses;
      }

      if (ses.acquire()) return ses;
      else sesMap.remove(sesId, ses);
    }
  }
  /**
   * Removes session for a given session ID.
   *
   * @param sesId ID of session to remove.
   * @return {@code True} if session was removed.
   */
  public boolean removeSession(GridUuid sesId) {
    GridTaskSessionImpl ses = sesMap.get(sesId);

    assert ses == null || ses.isFullSupport();

    if (ses != null && ses.release()) {
      sesMap.remove(sesId, ses);

      return true;
    }

    return false;
  }