ASP.NET Schedule deletion of temporary files

问题:

Question: I have an ASP.NET application which creates temporary PDF files (for the user to download). Now, many users over many days can create many PDFs, which take much disk space.

What's the best way to schedule deletion of files older than 1 day/ 8 hours ? Preferably in the asp.net application itselfs...

回答1:

For each temporary file that you need to create, make a note of the filename in the session:

// create temporary file:
string fileName = System.IO.Path.GetTempFileName();
Session[string.Concat("temporaryFile", Guid.NewGuid().ToString("d"))] = fileName;
// TODO: write to file

Next, add the following cleanup code to global.asax:

<%@ Application Language="C#" %>
<script RunAt="server">
    void Session_End(object sender, EventArgs e) {
        // Code that runs when a session ends. 
        // Note: The Session_End event is raised only when the sessionstate mode
        // is set to InProc in the Web.config file. If session mode is set to StateServer 
        // or SQLServer, the event is not raised.

        // remove files that has been uploaded, but not actively 'saved' or 'canceled' by the user
        foreach (string key in Session.Keys) {
            if (key.StartsWith("temporaryFile", StringComparison.OrdinalIgnoreCase)) {
                try {
                    string fileName = (string)Session[key];
                    Session[key] = string.Empty;
                    if ((fileName.Length > 0) && (System.IO.File.Exists(fileName))) {
                        System.IO.File.Delete(fileName);
                    }
                } catch (Exception) { }
            }
        }

    }       
</script>

UPDATE: I'm now accually using a new (improved) method than the one described above. The new one involves HttpRuntime.Cache and checking that the files are older than 8 hours. I'll post it here if anyones interested. Here's my new global.asax.cs:

using System;
using System.Web;
using System.Text;
using System.IO;
using System.Xml;
using System.Web.Caching;

public partial class global : System.Web.HttpApplication {
    protected void Application_Start() {
        RemoveTemporaryFiles();
        RemoveTemporaryFilesSchedule();
    }

    public void RemoveTemporaryFiles() {
        string pathTemp = "d:\\uploads\\";
        if ((pathTemp.Length > 0) && (Directory.Exists(pathTemp))) {
            foreach (string file in Directory.GetFiles(pathTemp)) {
                try {
                    FileInfo fi = new FileInfo(file);
                    if (fi.CreationTime < DateTime.Now.AddHours(-8)) {
                        File.Delete(file);
                    }
                } catch (Exception) { }
            }
        }
    }

    public void RemoveTemporaryFilesSchedule() {
        HttpRuntime.Cache.Insert("RemoveTemporaryFiles", string.Empty, null, DateTime.Now.AddHours(1), Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, delegate(string id, object o, CacheItemRemovedReason cirr) {
            if (id.Equals("RemoveTemporaryFiles", StringComparison.OrdinalIgnoreCase)) {
                RemoveTemporaryFiles();
                RemoveTemporaryFilesSchedule();
            }
        });
    }
}

回答2:

Try using Path.GetTempPath(). It will give you a path to a windows temp folder. Then it will be up to windows to clean up :)

You can read more about the method here http://msdn.microsoft.com/en-us/library/system.io.path.gettemppath.aspx

回答3:

The Best way is to create a batch file which it be called by the windows task scheduler one at the interval that you want.

OR

you can create a windows service with the class above

public class CleanUpBot
{

public bool KeepAlive;

private Thread _cleanUpThread;

public void Run()
{

_cleanUpThread = new Thread(StartCleanUp);

}

private void StartCleanUp()
{

do

{

// HERE THE LOGIC FOR DELETE FILES

_cleanUpThread.Join(TIME_IN_MILLISECOND);

}while(KeepAlive)

}

}

Notice that you can also call this class at the pageLoad and it wont affect the process time because the treatment is in another thread. Just remove the do-while and the Thread.Join().

回答4:

How do you store the files? If possible, you could just go with a simple solution, where all files are stored in a folder named after the current date and time.
Then create a simple page or httphandler that will delete old folders. You could call this page at intervals using a Windows schedule or other cron job.

回答5:

Create a timer on Appication_Start and schedule the timer to call a method on every 1 hours and flush the files older than 8 hours or 1 day or whatever duration you need.

回答6:

I sort of agree with whats said in the answer by dirk.

The idea being that the temp folder in which you drop the files to is a fixed known location however i differ slightly ...

1. Each time a file is created add the filename to a list in the session object (assuming there isn't thousands, if there is when this list hits a given cap do the next bit)

2. when the session ends the Session_End event should be raised in global.asax should be raised. Iterate all the files in the list and remove them.

回答7:

    private const string TEMPDIRPATH = @"C:\\mytempdir\";
    private const int DELETEAFTERHOURS = 8;

    private void cleanTempDir()
    {
        foreach (string filePath in Directory.GetFiles(TEMPDIRPATH))
        {
            FileInfo fi = new FileInfo(filePath);
            if (!(fi.LastWriteTime.CompareTo(DateTime.Now.AddHours(DELETEAFTERHOURS * -1)) <= 0)) //created or modified more than x hours ago? if not, continue to the next file
            {
                continue;
            }

            try
            {
                File.Delete(filePath);
            }
            catch (Exception)
            {
                //something happened and the file probably isn't deleted. the next time give it another shot
            }
        }
    }

The code above will remove the files in the temp directory that are created or modified more than 8 hours ago.

However I would suggest to use another approach. As Fredrik Johansson suggested, you can delete the files created by the user when the session ends. Better is to work with an extra directory based on the session ID of the user in you temp directory. When the session ends you simply delete the directory created for the user.

    private const string TEMPDIRPATH = @"C:\\mytempdir\";
    string tempDirUserPath = Path.Combine(TEMPDIRPATH, HttpContext.Current.User.Identity.Name);
    private void removeTempDirUser(string path)
    {
        try
        {
            Directory.Delete(path);
        }
        catch (Exception)
        {
            //an exception occured while deleting the directory.
        }
    }

回答8:

Use the cache expiry notification to trigger file deletion:

    private static void DeleteLater(string path)
    {
        HttpContext.Current.Cache.Add(path, path, null, Cache.NoAbsoluteExpiration, new TimeSpan(0, 8, 0, 0), CacheItemPriority.NotRemovable, UploadedFileCacheCallback);
    }

    private static void UploadedFileCacheCallback(string key, object value, CacheItemRemovedReason reason)
    {
        var path = (string) value;
        Debug.WriteLine(string.Format("Deleting upladed file '{0}'", path));
        File.Delete(path);
    }

ref: MSDN | How to: Notify an Application When an Item Is Removed from the Cache