Question

In the web app that I’m currently working on I’ve to make multiple calls to database and combine the results at-last to show in the UI. Right now.. I’m doing the calls one by one and combining the results at last. Since the web app will be hosted in a multi-core machine(intel i5) I think I can use TPL to make parallel db calls. Is it a good idea? What are the things/pitfalls I want to consider when I’m doing parallel calls to db?

Answer 1

There are two things to remember here. Firstly you’re DB provided API may not be thread-safe, for example ADO.NET explicitly isn’t 100% thread-safe. Secondly by doing this you are moving your load from the clinet to the DB. In other words if your client creates 5 concurrent connections to the DB at once it’s going to have a larger impact on the DB’s load. The latency of an individual client to the user may be reduced but at the expense of overall throughput in terms of the number of clients an individual DB can support.

If largely depends on your scenario as to whether you think this is a good tradeoff.

You say the “we app” if you mean web app then their are similar tradeoffs, I’d recommend this blog post on using the TPL from a web application.

http://blogs.msdn.com/b/pfxteam/archive/2010/02/08/9960003.aspx

It’s the same issue. You trade of individual request latency for throughput or vis versa.