what is the right way to spawn thread for database IO in asmx web service?

Question

I have a short lock guarded section in a method (that serves the request entirely) that makes all initializations (etc. log-related). So only 1 thread can be there at time. In

Answer 1

Matti, you're asking multiple questions that point to the best structure for your application. I would summarize your questions as:

• How do I pre-load data needed by my service prior to handling any legitimate requests?
• How do I ensure the pre-loaded data is loaded "once"?
• How do I refresh the pre-loaded data on a schedule, i.e. every 24 hours?

Understanding the Asp.Net pipeline and event structure will help you understand the answers to these questions.

First, the Asp.Net pipeline provides a one-time execution region in Application_Start. This is fired once per application cycle. This would also fire in 'iisreset', which cycles every application for a given server. However, application cycles themselves will recycle on their own, based on their configuration. All of which are controlled through IIS settings.

Second, Asp.Net is a request system; it won't fire refresh events for you, nor can you use it by itself as a scheduler. You need an outside agent to act on that for you.

Here's what you could do:

1. Add your pre-loaded data routine to Application_Start.
2. Configure your web site's Application cycle settings for every 24 hours.

This would ensure your data is loaded once, via Application_Start. It would ensure your data is loaded prior to your site serving any requests. Last, it would ensure your data is refreshed every 24 hours.

Here's what I would do:

1. Add pre-loaded data routine to Application_Start.
2. Modify pre-loaded data routine to use Asp.Net Cache, instead of static usage.
3. Modify lookup data to retrieve data from cache, and re-load if data is not found.
4. Provide capability for diagnostic/monitoring system, i.e. nagios, to refresh data asynchronously via web method call, i.e. "preload_refresh()".

This would provide essentially the same forward effect as the above solution, but with better reliability for your service.

As always, your mileage may vary. Hope this helps.

Answer 2

To answer part of your question anyway, you can use the "Application_Start" method in the Global.asax to execute the statement on the start of the application if you want to pre-fill the data as soon as the application comes online.