Question

I’m having an issue with the Singleton pattern.

It is really weird, but it looks like there are two or three instances of my Singleton Pattern.
My website, is an actions site, with timers and I’m handling those timers and prices with my Singleton Object.

What is happening is that some people see some prices, and other people see other prices always when they are in different networks.

For example, In my office, my people see some auction at 0.56 cents, everybody sees the same, but in another network, for example, my house, I see 0.55 cents and also the timers have different values.

Having said this, I’ve tested my Singleton, by generating a GUID and logging it in my log file. Here is some code

public class Singleton
{
    private static Singleton instance;
    private static System.Threading.Mutex mutex;

    System.Guid token;

    private Singleton() { 
        token = System.Guid.NewGuid();
        Logger.Log("New singleton Instance" + token.toString());
    }
    static Singleton()
    {
        instance = new Singleton();
        mutex = new System.Threading.Mutex();
    }

    public static Singleton Acquire()
    {
        mutex.WaitOne();
        return instance;
    }

    // Each call to Acquire() requires a call to Release()
    public static void Release()
    {
        mutex.ReleaseMutex();
    }

    public void SomeAction()
    {
       Logger.Log(token.toString() + " - SomeAction");
    }
}

In this code, I generate the token on the constructor, and log the creation of a new Singleton, then… in the SomeAction method, I log who is doing that action.

After this, we made a couple of tests and downloaded the log file.

To my surprise, I see only one “New Singleton Instance bla” which is correct. but then, many calls to the SomeAction Method with different GUIDs, which is weird.

I checked that object is only created in the static constructor, and I also checked that there is no manual creation anywhere.

For more information, this only happens on my production server, which is a goDaddy hosting. I’ve asked if there is more than one application pool for my website and they say there is only one app Pool.

Answer 1

Your singleton lifetime is tied to the current worker process of IIS.

If you have multiple worker processes configured then not all of the requests are handled by the same process and thus not the same singleton.