xenadmin/XenModel/Actions/Updates/DownloadAndUnzipXenServerPatchAction.cs

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using System;
using System.Net;
using System.ComponentModel;
using System.Threading;
using System.IO;
using XenCenterLib.Archive;

namespace XenAdmin.Actions
{
    internal enum DownloadState { InProgress, Cancelled, Completed, Error };

    public class DownloadAndUnzipXenServerPatchAction : AsyncAction
    {
        private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        private const int SLEEP_TIME_TO_CHECK_DOWNLOAD_STATUS_MS = 900;
        private const int MAX_NUMBER_OF_TRIES = 5; //If you consider increasing this for any reason (I think 5 is already more than enough), have a look at nextSleepMs in DownloadFile() as well.
        private Random random = new Random();

        private readonly Uri address;
        private readonly string outFileName;
        private readonly string updateName;
        private readonly string updateFileExtension;
        private DownloadState patchDownloadState;
        private Exception patchDownloadError;

        public string PatchPath
        {
            get; private set;
        }

        public DownloadAndUnzipXenServerPatchAction(string patchName, Uri uri, string outputFileName)
            : this(patchName, uri, outputFileName, InvisibleMessages.XEN_UPDATE)
        { }

        public DownloadAndUnzipXenServerPatchAction(string patchName, Uri uri, string outputFileName, string updateFileExtension)
            : base(null, string.Format(Messages.DOWNLOAD_AND_EXTRACT_ACTION_TITLE, patchName), string.Empty, false)
        {
            updateName = patchName;
            address = uri;
            outFileName = outputFileName;
            this.updateFileExtension = updateFileExtension;
        }

        private void DownloadFile()
        {
            int errorCount = 0;
            int nextSleepMs = 0;
            bool needToRetry = true;

            while (errorCount < MAX_NUMBER_OF_TRIES && needToRetry)
            {
                needToRetry = false;

                using (var client = new WebClient())
                {
                    try
                    {
                        //register download events
                        client.DownloadProgressChanged += client_DownloadProgressChanged;
                        client.DownloadFileCompleted += client_DownloadFileCompleted;
                        //start the download
                        client.DownloadFileAsync(address, outFileName);

                        patchDownloadState = DownloadState.InProgress;
                        bool patchDownloadCancelling = false;

                        //wait for the file to be downloaded
                        while (patchDownloadState == DownloadState.InProgress)
                        {
                            if (!patchDownloadCancelling && (Cancelling || Cancelled))
                            {
                                Description = Messages.DOWNLOAD_AND_EXTRACT_ACTION_DOWNLOAD_CANCELLED_DESC;
                                client.CancelAsync();
                                patchDownloadCancelling = true;
                            }
                            Thread.Sleep(SLEEP_TIME_TO_CHECK_DOWNLOAD_STATUS_MS);
                        }

                        if (patchDownloadState == DownloadState.Cancelled)
                            throw new CancelledException();

                        if (patchDownloadState == DownloadState.Error)
                        {
                            needToRetry = true;

                            // this many errors so far - including this one
                            errorCount++;

                            // logging only, it will retry again.
                            log.ErrorFormat("Error while downloading from '{0}'. Number of errors so far (including this): {1}. Trying maximum {2} times.", address, errorCount, MAX_NUMBER_OF_TRIES);
                            log.Error(patchDownloadError ?? new Exception(Messages.ERROR_UNKNOWN));
                            
                            // wait for some randomly increased amount of time after each retry
                            nextSleepMs += random.Next(5000);
                            Thread.Sleep(nextSleepMs);
                        }
                    }
                    finally
                    {
                        //deregister download events
                        client.DownloadProgressChanged -= client_DownloadProgressChanged;
                        client.DownloadFileCompleted -= client_DownloadFileCompleted;
                    }
                }
            }

            //if this is still the case after having retried MAX_RETRY number of times.
            if (patchDownloadState == DownloadState.Error)
            {
                log.ErrorFormat("Giving up - MAX_NUMBER_OF_RETRIES_IF_FAILED has been reached.");
                            
                MarkCompleted(patchDownloadError ?? new Exception(Messages.ERROR_UNKNOWN));
            }

        }

        private void ExtractFile()
        {
            ArchiveIterator iterator = null;
            try
            {
                using (Stream stream = new FileStream(outFileName, FileMode.Open, FileAccess.Read))
                {
                    iterator = ArchiveFactory.Reader(ArchiveFactory.Type.Zip, stream);
                    DotNetZipZipIterator zipIterator = iterator as DotNetZipZipIterator;
                    if (zipIterator != null)
                    {
                        zipIterator.CurrentFileExtractProgressChanged +=
                            archiveIterator_CurrentFileExtractProgressChanged;
                    }

                    while (iterator.HasNext())
                    {
                        string currentExtension = Path.GetExtension(iterator.CurrentFileName());

                        if (!string.IsNullOrEmpty(updateFileExtension) && currentExtension == "." + updateFileExtension)
                        {
                            string path = Path.Combine(Path.GetDirectoryName(outFileName), iterator.CurrentFileName());

                            log.DebugFormat("Found '{0}' in the downloaded archive when looking for a '{1}' file. Extracting...", iterator.CurrentFileName(), currentExtension);

                            using (Stream outputStream = new FileStream(path, FileMode.Create))
                            {
                                iterator.ExtractCurrentFile(outputStream);
                                PatchPath = path;

                                log.DebugFormat("Update file extracted to '{0}'", path);
                                
                                break;
                            }
                        }
                    }

                    if (zipIterator != null)
                    {
                        zipIterator.CurrentFileExtractProgressChanged -=
                            archiveIterator_CurrentFileExtractProgressChanged;
                    }
                }
            }
            catch (Exception e)
            {
                log.ErrorFormat("Exception occurred when extracting downloaded archive: {0}", e.Message);
                throw new Exception(Messages.DOWNLOAD_AND_EXTRACT_ACTION_EXTRACTING_ERROR);
            }
            finally
            {
                if (iterator != null)
                    iterator.Dispose();
                File.Delete(outFileName);
            }
            
            if (string.IsNullOrEmpty(PatchPath))
            {
                MarkCompleted(new Exception(Messages.DOWNLOAD_AND_EXTRACT_ACTION_FILE_NOT_FOUND));
                log.DebugFormat("File '{0}.{1}' could not be located in downloaded archive", updateName, updateFileExtension);
            }
        }

        protected override void Run()
        {
            log.DebugFormat("Downloading XenServer patch '{0}' (url: {1})", updateName, address);

            Description = string.Format(Messages.DOWNLOAD_AND_EXTRACT_ACTION_DOWNLOADING_DESC, updateName);
            LogDescriptionChanges = false;
            DownloadFile();
            LogDescriptionChanges = true;

            if (IsCompleted || Cancelled)
                return;

            if (Cancelling)
                throw new CancelledException();

            log.DebugFormat("Extracting XenServer patch '{0}'", updateName);
            Description = string.Format(Messages.DOWNLOAD_AND_EXTRACT_ACTION_EXTRACTING_DESC, updateName);
            ExtractFile();
            log.DebugFormat("Extracting XenServer patch '{0}' completed", updateName);

            Description = Messages.COMPLETED;
            MarkCompleted();
        }

        void archiveIterator_CurrentFileExtractProgressChanged(object sender, ExtractProgressChangedEventArgs e)
        {
            int pc = 95 + (int)(5.0 * e.BytesTransferred / e.TotalBytesToTransfer);
            if (pc != PercentComplete)
                PercentComplete = pc;
        }

        void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            int pc = (int)(95.0 * e.BytesReceived / e.TotalBytesToReceive);
            if (pc != PercentComplete)
            {
                PercentComplete = pc;
                Description = string.Format(Messages.DOWNLOAD_AND_EXTRACT_ACTION_DOWNLOADING_DETAILS_DESC, updateName,
                                            Util.DiskSizeString(e.BytesReceived),
                                            Util.DiskSizeString(e.TotalBytesToReceive));
            }
        }

        void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            if (e.Cancelled) //user cancelled
            {
                patchDownloadState = DownloadState.Cancelled;
                log.DebugFormat("XenServer patch '{0}' download cancelled by the user", updateName);
                return;
            }

            if (e.Error != null) //failure
            {
                patchDownloadError = e.Error;
                log.DebugFormat("XenServer patch '{0}' download failed", updateName);
                patchDownloadState = DownloadState.Error;
                return;
            }

            //success
            patchDownloadState = DownloadState.Completed;
            log.DebugFormat("XenServer patch '{0}' download completed successfully", updateName);
        }

        public override void RecomputeCanCancel()
        {
            CanCancel = !Cancelling && !IsCompleted && (patchDownloadState == DownloadState.InProgress);
        }

        protected override void CancelRelatedTask()
        {
        }
    }
}