在ASP.NET中使用WCF服务，如何缓存？

Question

I have two situations in this case:

I want to query a WCF service and hold the data somewhere, because one of the web pages renders based on the data that's retrieved from the service. I don't want the page itself querying the service, but I'd rather have some sort of scheduled worker that runs once every a couple of minutes, and retrieves the data and holds it somewhere.

Where should I cache the service response, and what is the correct way to create the task to query the service every couple minutes?

I think I could achieve this by saving the response to a static variable, alongside the last query date, and then check on the page load if enough time has passed, I call the service and refresh the data, else I use the static cache.

This would also account for the case where no users access the page for a long time, and the site not futilely querying the service.

But it seems kind of rough, are there other, better ways to accomplish this kind of task?

Answer 1

你看过速度了吗

Answer 2

You could indeed take another approach like having a scheduled program query the information and put it in an in-memory cache available to all the web servers in your farm. However, whether that would be better for your scenario depends on the size of your app and how much time/effort you want to spend on it.

An in-memory cache is harder to implement/support than a static variable but it's sometimes better since static variables can be cleared up every time the server resets (eg after X number of minutes of inactivity)

Depending on the size of your system I would start with the static variable, test drive the approach for a while and then decide if you need something more sophisticated.

Answer 3

Nico: Why don't you write a simple console daemon that gets the data and stores it on your end in a database and then have your web app get the data from your local copy? You can make that console app run every certain amount of time. Inserting the data should not be a problem if you are using sql server 2008. You can pass datatable parameters to a stored proc and insert a whole table in one call. If you don't use Sql Server 2008, then serialize the whole collection returned by the web service and store in a table in one big blob column and record the timestamp when you got the data. You then can read the content of that column, deserealize your collection and reconstruct it to native objects for displaying on your page.

I've never seen (and I don't think its possible) to have your web app query the web service every certain amount of time. Imagine the web site is idle for hours therefore no interaction from anybody. That means that no events will fire and nothing will be queried.

Alternatively, you could create a dummy page executing a javascript function at certain intervals and have that javascript function make an ajax request to the server to get the data from the web service and cache the data. The problem is that the minute you walk out of that page, nothing will happen and you'll stop querying the web service. I think this is silly.