Always Name Your Thread Pools
Make life a little easier for the non-Spring folk.
Join the DZone community and get the full member experience.Join For Free
Our software tends to use a lot of thread pools – mostly through
java.util.concurrent.ExecutorService implementations (Created via
Executors.new.... We create these for various async use-cases, and they can be seen all over the place. All of these executors have a thread factory. It’s hidden in the default factory method, but you can supply a thread factory. If not supplied, a default thread factory is used whenever a thread is needed.
When using Spring, those can be created using
<task:executor />. In that case, each executor service’s thread factory is provided by Spring and it uses the name of the executor bean (specified with
id="executorName"). But for those not created by Spring, a default name is used, which isn’t helpful and doesn’t let you differentiate threads by name.
And you need to differentiate threads by name – in case of performance issues you have various options to investigate: thread dumps and using the top command. In both cases, it’s useful to know what function does a thread service, as the stacktrace in the dump might not always be revealing.
And my favorite tool for quick investigation is
top. More precisely,
top -H -p <pid>. This shows the usual top table, but the -H flag means that threads for the chosen process should be printed. You basically get the most CPU-heavy and currently active threads, by name. In those cases, it’s extremely useful to have custom names.
But how do you set a name? By specifying a named thread factory when creating each executor. Here’s a StackOverflow answer with multiple ways to achieve thread naming.
The method that I’m using is based on the 2nd answer:
Centrally managing all executors through Spring might be a better idea, but not everyone is using Spring and sometimes an executor is needed for a small piece of functionality that could even go outside Spring Beans. So it’s a good idea to have that method up your sleeve.
Published at DZone with permission of Bozhidar Bozhanov, DZone MVB. See the original article here.
Opinions expressed by DZone contributors are their own.