How to check how many users are online?

Question

I administer a ASP.NET website that has decent traffic. In the middle of the day, I sometimes would need to either redeploy the website, change the configuration in the web.config file or make some update to the SQL Server.

In theory, when I make these changes, I can redirect the user to a "Maintainence page" that indicates that updates are in progress. But sometimes, the fix usually takes only a few seconds.

How would I check how many users are using the website and apply the quick changes when no one is online? I do have access to the web server and the database server.

Solution

You could monitor active connections in real-time using System Monitor (type perfmon in the Run dialog box). Add the "Web Service" counter to monitor active Web connections.

Here is a list of performance counters for IIS 6.0 (Microsoft Technet).