[wildfly-dev] Pooling EJB Session Beans per default

[Jason Greene]

On Aug 5, 2014, at 8:43 AM, Andrig Miller <anmiller at redhat.com> wrote:

> 
> 
> ----- Original Message -----
>> From: "Bill Burke" <bburke at redhat.com>
>> To: "James Livingston" <jlivings at redhat.com>
>> Cc: wildfly-dev at lists.jboss.org
>> Sent: Tuesday, August 5, 2014 7:32:04 AM
>> Subject: Re: [wildfly-dev] Pooling EJB Session Beans per default
>> 
>> 
>> 
>> On 8/4/2014 8:44 PM, James Livingston wrote:
>>> On Mon, 2014-08-04 at 20:22 -0400, Bill Burke wrote:
>>>> I always liked the ThreadLocal pool.   No synchronization, little
>>>> to no
>>>> allocations.
>>> 
>>> It also can cause massive memory leaks if invoked from threads
>>> which
>>> aren't re-used, like timer threads, and precautions aren't taken.
>>> AS/EAP
>>> 5 suffered from that problem with the default ThreadLocalPool.
>>> 
>> 
>> Which is also something that could be mitigated by a common thread
>> facility.  Something AS/EAP 5 didn't have.
>> 
>> Honestly though, I think this talk of EJB pooling is ridiculous.
>> Component layers like CDI and JAX-RS don't have pooled architectures
>> for
>> their per-request objects.  Also, in an average application, there
>> are
>> multiple orders of magnitude more non component classes that are
>> being
>> instantiated per request.  Just think of all the Strings created by a
>> simple HTTP request.
>> 
>> You want a better focus?  How about JSON/XML marshalling?  Which
>> could
>> make things much easier to maintain then the hand-coded parsers that
>> Wildfly uses to parse config.  And much faster and less memory at
>> runtime for SOAP and JAX-RS request that currently rely on java
>> reflection.
>> 
>> You could go research perfect hashing algorithms for URL matching
>> with
>> servlets and JAX-RS.
>> 
>> You could go do some perf analysis of all of our frameworks to make
>> memory reduction and speed recommendations or even Pull Requests.
>> 
>> You could visit each major project and make sure our automated builds
>> have and can run automated stress tests and are measured against
>> previous versions.
>> 
>> Or you could just focus on these silly benchmarks that test no-op
>> HTTP
>> and EJB requests.
>> 
> 
> Those silly benchmarks, are indeed silly.  Any workload that doesn't actually do anything with the requests is not very helpful.  You can be really fast on them, and be really slow on a workload that actually does something.  We have already seen this in one case recently.

It’s all about precision, and limiting variables. I know its fun to criticize micro benchmarks (obviously micro is indeed relative because a great deal of processing goes on even when you have EJB and HTTP requests that don’t do much), however micro benchmarks, provided they are measured correctly, are quick to run and make it easy to tell what you have to fix. Large gigantic apps on the other hand are difficult to analyze, and do not necessarily represent activity that a differently architected app would show. To use an example, if you have pattern matching code, and you want it to be fast, it’s much easier (and accurate) to benchmark the pattern matching code then it is to benchmaark a full EE app that happens to use pattern matching in a few places.

Arguing against targeted benchmarks is like arguing that you should never write a test case, because only real production load will show problems…. To some extent thats true, but that doesn’t mean that the problems you catch in simulations won’t affect production users. 

--
Jason T. Greene
WildFly Lead / JBoss EAP Platform Architect
JBoss, a division of Red Hat