[jboss-as7-dev] Limiting Server Thread Usage

[Carlo de Wolf]

We should actually invert the model (especially for EJB remote invocations).

Instead of having threads blocking on pool constraints, make the pool 
leading in thread management.

Carlo

On 09/14/2011 09:03 PM, Scott Stark wrote:
> 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.
>>    >
>>
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