xenadmin/XenModel/Actions/ParallelAction.cs

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using System;
using System.Collections.Generic;
using System.Threading;
using XenAdmin.Network;
using XenAPI;


namespace XenAdmin.Actions
{
    /// <summary>
    /// ParallelAction takes a list of any number of actions and runs a certain number of them simultaneously.
    /// Once one simultaneous action is finished the next one in the queue is started until all are complete
    /// </summary>
    public class ParallelAction : MultipleAction
    {
        private int numberOfSimultaneousActions = 25;

        /// <summary>
        /// Number of actions to be run at the same time
        /// </summary>
        public int NumberOfSimultaneousActions
        {
            set { numberOfSimultaneousActions = value; }
        }

        //Change parameter to increase the number of concurrent actions running
        private readonly ProduceConsumerQueue _queuePC;

        public ParallelAction (IXenConnection connection, string title, string startDescription, string endDescription, List<AsyncAction> subActions)
            : base(connection, title, startDescription, endDescription, subActions)
        {
            _queuePC = new ProduceConsumerQueue(subActions.Count < numberOfSimultaneousActions ? subActions.Count : numberOfSimultaneousActions);
        }

        protected override void RunSubActions(List<Exception> exceptions)
        {
            foreach (AsyncAction subAction in subActions)
            {
                AsyncAction action = subAction;
                action.Completed += new EventHandler<EventArgs>(action_Completed);
                _queuePC.EnqueueItem(
                    () =>
                    {
                        try
                        {
                            action.RunExternal(Session);
                        }
                        catch (Exception e)
                        {
                            Failure f = e as Failure;
                            if (f != null && Connection != null &&
                                f.ErrorDescription[0] == Failure.RBAC_PERMISSION_DENIED)
                            {
                                Failure.ParseRBACFailure(f, Connection, Session ?? Connection.Session);
                            }
                            exceptions.Add(e);
                            // Record the first exception we come to. Though later if there are more than one we will replace this with non specific one.
                            if (Exception == null)
                                Exception = e;
                        }
                    });

            }
            lock (_lock)
            {
                Monitor.Wait(_lock);
            }
        }

        private readonly object _lock = new object();
        private volatile int i = 0;
        void action_Completed(object sender, EventArgs e)
        {
            lock (_lock)
            {
                i++;
                PercentComplete = 100 * i / subActions.Count;
                if (i == subActions.Count)
                    Monitor.Pulse(_lock);
            }
        }

        protected override void MultipleAction_Completed(object sender, EventArgs e)
        {
            
            base.MultipleAction_Completed(sender, e);
            _queuePC.StopWorkers(false);
        }
    }
}