The short circuit article

About three and a half years ago I co-wrote an article named “Increase stability and responsiveness by short-circuiting code” for IBM’s developer works site, and for some reason in the past few days it has repeatedly asked for attention (“hi this is 2004, your article is on the line, and its woefully dated”). First, the one page abstract we submitted fell out of a book on my bookshelf, then I was asked about it at at least one interview. Sadly, that was one of the top results for my name in google for a while and people still find it.
I figure its about time to revisit, and disavow, the implementation in the article, if that isn’t already obvious to anyone.

The idea was to provide a way to time-box operations that could take an unknown amount of time. In this way for example, a web page that must be displayed faster than a certain time can be guaranteed to run in that time, if it can do without the results of operations that take too long to execute.
One obvious flaw is that the code creates LOTS of new threads for a short period of time. It should have used a thread pool to reduce that churn.
The best reason not to use that code is that Java 1.5 introduced a whole set of Concurrency utilities. ExecutorService and Future. There are lots of examples about, so you can check them out.

The high level view is that you package your functionality in a Runnable or Callable (depending if you need to return a result), submit it to an instance of ExecutorService to run. It will return a Future object which can be queried to get the result. One can call get on the Future class, which will return right away if the task is done execuiting, or block until the sooner of a specified timeout or the task completing. Even better, one can submit multiple tasks at once with invokeAll(..) and that will return when all tasks are complete or the timeout has expired.

Leave a Reply

Your email address will not be published.