AzamSharp

# re: Implementing Hit Counters in Asp.net

This is a good example for a simple crosscutting concern that can be implemented in an http module to be reused in all your asp.net applications. For performance reasons it might make sense to store the counter in a singleton instead of Application[...] to avoid the lookup in the hashtable (especially when you track requests) 7/20/2005 1:18 PM | fx

# re: Implementing Hit Counters in Asp.net

Thanks for the comment. I will check if I can implement Singleton on this and remove Application variable. 7/20/2005 2:03 PM | AzamSharp

# re: Implementing Hit Counters in Asp.net

Don't you think the counter needs to be locked while being incremented ? 7/21/2005 2:57 AM | enaoui@hotmail.Com

# re: Implementing Hit Counters in Asp.net

You are right ! You can use the lock keyword in C# to lock the Counter. 7/21/2005 5:13 AM | Azamsharp

# re: Implementing Hit Counters in Asp.net

I mean Application.Lock() and Application.Unlock()

:) 7/21/2005 7:20 AM | AzamSharp

# re: Implementing Hit Counters in Asp.net

Using lock and unlock for incrementing the counter will have a very negative effect on performance because concurrent requests will be locked. The only time I'd lock is when you dump the counter to the db, otherwise a counter singleton will do just fine

Even when persisting your counter I'd be very wary about using such a global lock like Application.Lock 7/21/2005 8:24 AM | fx

# re: Implementing Hit Counters in Asp.net

You are right ! It will kill performance. Let me know the details of your counter Singleton pattern.


You can than use the lock keyword of C#.

Thanks,
AzamSharp 7/21/2005 8:38 AM | AzamSharp

# re: Implementing Hit Counters in Asp.net

You could use a class like this to instantiate counters for your needs (see counterID):

public class Counter
{
// Identifier for counter (e.g. "Sessions", "Requests", "Errors")
private string _counterID;
public string CounterID
{
get { return (this._counterID); }
}

private int _persistenceThreshold=1000;
public int PersistenceThreshold
{
get { return (this._persistenceThreshold); }
}

private int _currentValue;
public int CurrentValue
{
get { return (this._currentValue); }
}

private int tempCounter=0;

public Counter(string id)
{
_counterID=id;
Load();
}

public Counter(string id, int threshold) : this(id)
{
_persistenceThreshold = threshold;
}

private void Load()
{
// Get the last counter value from persistentent storage (db, file, PerfCounter)
}

private void Save()
{
lock (this)
{
if (tempCounter > 0)
{
// Save counter to persistent storage (db, file, PerfCounter)
tempCounter = 0;
}
}
}

public void Increment()
{
_currentValue++;
if (tempCounter > PersistenceThreshold)
{
Save();
}
tempCounter++;
}
}

and then add in the http module:



public class CounterModule : IHttpModule
{
...
private Counter _requestCounter = new Counter("Request", 1000);
private Counter _errCounter = new Counter("Error", 10);
... // other counters

public void OnBeginRequest(Object s, EventArgs e)
{
_requestCounter.Increment();
}

public void OnError(Object s, EventArgs e)
{
_errCounter.Increment();
}

}

Then all you need to do is to register CounterModule in your web.config and
you should be good to go (Alternatively you can just hook them into Global.asax)

Of course the whole thing is kind of a void exercise, since the .Net Perfcounters were specifically designed for the task at hand
7/21/2005 1:42 PM | fx

# re: Implementing Hit Counters in Asp.net

Thanks a lot ! I will check your code :)

7/21/2005 2:23 PM | AzamSharp

# re: Implementing Hit Counters in Asp.net

There are two things that would worry me about fx's code:

1) It looks like the code is assuming there will be only one CounterModule created in an application. There will almost always be multiple instances of an HttpModule instantiated by the runtime - this will throw the counts off. You can use static int members to share the value across module instances.

2) The ++ operator isn't thread-safe - use Interlocked.Increment instead. 7/26/2005 5:59 PM | Scott Allen