Microsoft released the Windows 8.1 Preview on June 26, but some of the articles that the IIS team was working on for IIS 8.5 needed a little more work before we published them. That being said, those articles were published on IIS.net earlier today, and here is a quick preview of those articles and the new features in IIS 8.5 which they describe:

  • Dynamic Website Activation in IIS 8.5
    This feature allows IIS to scale to an even larger set of websites than before by only loading websites after an HTTP request has been received; this significantly reduces the startup time and initial resource allocation for IIS, and it prevents resources from being unnecessarily consumed for websites that are accessed infrequently.
  • Enhanced Logging for IIS 8.5
    IIS now provides built-in functionality for adding custom logging fields to your W3C log files that are populated with values that are from request headers, response headers, or server variables. This functionality allows you to log a great deal of custom information about each HTTP request; for example, you could include the information an HTTP header like X-Forwarded-For, which would allow you to decode the request path through all firewalls/proxies, or you could insert information from a custom module into a server variable and have IIS add that information directly to your logs.
  • Idle Worker Process Page-Out in IIS 8.5
    In previous versions of IIS, inactive worker processes were terminated when they reached their recycle interval, but IIS 8.5 allows you to configure your application pools so that inactive worker processes are swapped out to the page file; since IIS can restore a suspended worker process into service much faster than starting up a new worker process, this functionality significantly improves the user experience when a request is received for a suspended application.
  • Logging to Event Tracing for Windows in IIS 8.5
    IIS 8.5 expands the logging capabilities for HTTP events to include Event Tracing for Windows (ETW); this functionality allows you monitor your IIS events in real-time, which can be extremely useful for troubleshooting and debugging/developing applications.

For examples of these technologies in action, you can watch one of the following presentations:

Special thanks go to Gary Ericson for putting together and publishing these articles on IIS.net, and a big round of thanks to the IIS team for adding all of these new features!

(One quick note in closing: functionality similar to IIS 8.5's Enhanced Logging was available in the past by installing separate modules, but IIS 8.5 now makes this functionality available out-of-the-box.)