[jax-rs-spec users] [jsr339-experts] Re: Filters: comparison of proposed options

From: Bill Burke <>
Date: Thu, 08 Dec 2011 08:17:12 -0500

On 12/8/11 4:27 AM, Marek Potociar wrote:
> On 12/07/2011 10:29 PM, Bill Burke wrote:
>> On 12/7/11 5:26 AM, Marek Potociar wrote:
>>> Now I am not saying that we should address such scenarios right away or that we should expose our users to any complex
>>> implementation details around fork-join or any other execution strategy. But this is just to demonstrate what we may
>>> expect to deal with in the future, esp. if we, as implementors, want to leverage the parallel/async execution to gain
>>> performance boosts. That should help us to produce design flexible enough to support these types of scenarios. If all
>>> that we have to do right now is to convert an existing enum into an opaque interface and add bunch of action methods
>>> into the FilterContext, then I wonder why don't we just do it?
>> Running filters in parallel for the same request seems pretty crazy to me. In fact, its kinda silly. The context
>> switching/joining alone would kill any performance gains you made. Plus, any modicum of request concurrency will
>> already max out the cores of your CPU(s). All this crazy I/O you're talking about would rarely (if ever) happen in a
>> filter. It would happen in application code.
> Are you suggesting that all the caching, logging, auth etc. which IMHO may typically happen in a filter does not involve
> any I/O? Also, your idea that even a small amount of request concurrency necessarily leads to maxed CPU utilization is
> just false. With blocking I/O and synchronous processing I can easily craft a DoS attack that will occupy all the
> available threads and still the CPU will be just waiting idle most of the time.

By "small amount" I mean like 10-20 concurrent requests (not
connections, requests). You could create a DoS attack that could
probably kill any implementation.

Take a step back and think of what you're suggesting. The thought of
designing a system so that some time in the future somebody might want
to run a set of filters concurrently is just plain over-engineering.
Specifically when this would be an extreme edge case.

Bill Burke
JBoss, a division of Red Hat