Re: [jboss-as7-dev] Limiting Server Thread Usage
The question of whether this is the right limit is one I have raised,
especially since the limit is being imposed via a pam_limits module
which actually limits the number of processes a user is allowed. A java
thread is mapping to a process in this model, which further blurs the
effectiveness/validity.
However, this is an issue that does commonly come up with system admins
as a way of gauging max requests and therefore some measure of the max
resource requirements.
Perhaps a global limit is really not an effective approach.
Similar to how we have a global view of ports in use, perhaps just
having a global view of the thread pools in the domain model stats would
be enough. If I can see of the server thread pools with the min/max
settings, and there is a base thread pool dsl for min/max settings in
every subsystem utilizing a thread pool, one can at least understand the
thread usage, and make some choices about how to limit it.
On 9/14/11 10:53 AM, Jason T. Greene wrote:
Moving to a new thread.
The big problem we run into with this is that almost every application
of a thread pool that we have needs to be highly tailored to its usage
to get the most optimal performance. So we end up with quite a few
different pools and it becomes difficult to impose a server wide limit.
There however some potential strategies we could take. Although I am
unsure as to how the overall effectiveness would be:
1. Sharing idle threads between pools
2. Force everything to go through a special blocking thread factory via
instrumentation of java.lang.Thread. Any attempt to allocate over the
max would lead to thread reclamation attempts and finally blocking until
a timeout is reached.
3. Some kind of auto-tuning weighting model. If the max total threads is
N, force all thread pools to use a percentage of N, potentially based on
establishing current config value divided by combined total.
One thing I wonder though is if cloud providers are "barking up the
wrong tree"? It seems a better limitation of an application is raw CPU
clock time and max memory usage. How they split that time into threads
doesn't really affect the scalability of the physical server, it's all
virtual process performance (who cares if someone wastes time context
switching?).
On 9/14/11 10:39 AM, Scott Stark wrote:
> The other big cross cutting concern is controlling the total number of
> threads in use by the application server. When running under a
> constrained environment that uses something like pam_limits module to
> control how many process(==java threads) a user can have, it is
> difficult to know what the server max thread usage is right now.
>