As was kind of discussed earlier, TPE uses max threads in a different way then
most people would think.
It creates up to min threads, as long as the "queue is not full" (offer()
succeeding is "not full"). When the queue is "full", it creates up to
maxPoolSize threads for (maxPoolSize-corePoolSize) more adds.
So for an open ended queue, maxPoolSize has no meaning, and only corePoolSize
threads will ever be created it looks to me.
I think there are still bugs to be fixed and behavior to be better defined in
TPE in particular. I'm all for using the interfaces in j.u.c that make sense to
use. But I am a bit worried about swapping out TaskManager for TPE without a
lot more studying around the exact behaviors and failure modes, which might help
identify some issues we need to address overall regarding how threads are managed.
For example, the default life of 15mins on threads created by TaskManager in its
current version, seems extreme. 15 seconds would be much better for resource
management I think.
Gregg Wonderly
Patrick Wright wrote:
One point I'd like to raise about using java.util.concurrent and TPE:
I think that over the long term, it makes sense to (re)use existing
utilities which are being maintained by domain experts rather than
custom utilities you've written yourself. The concurrent libraries
available since Java 5 were written and maintained by people widely
recognized to be very, very good at a very hard problem. That doesn't
mean they, or the library, is perfect, just that there is value in
building on their work and letting them take care of the bugs and
optimizations over time. The downside would be that if a River user
was stuck with, say, Java 5, they couldn't take advantage of bugfixes
or improvements in Java 6. On the other hand, that's true of the
entire JDK.
The max threads issue seems to me a non-issue. A JVM can allocate only
so many native threads before it runs out of OS resources; that's a
hard limit. You can set a max of Integer.MAX_VALUE but your VM would
die long, long before it reached that.
For me this is more of design policy decision. Re-use, intelligently
and selectively, where possible, to reduce your project's workload.
Patrick
