Re: Concurrent request handling
Re: Concurrent request handling
- Subject: Re: Concurrent request handling
- From: Mark Wardle <email@hidden>
- Date: Fri, 08 Apr 2011 08:39:38 +0100
Thanks for this. I'm doing a quick code review!
b/w
Mark
On 5 April 2011 18:48, Chuck Hill <email@hidden> wrote:
> Hi Mark,
>
> On Apr 4, 2011, at 11:20 PM, Mark Wardle wrote:
>
>> Hi all,
>>
>> There have been a number of threads discussing this runtime option. I
>> think the consensus opinion was that although it is off by default, it
>> is better switched on.
>
> I think it is off by default to match the previous (now ancient) functionality.
>
>
>> Presumably there are some basic additional rules to follow.
>
> The EOF Commandments (as usual) plus:
>
> Don't Do Stupid Things
>
>
>
>> For instance, AFAIK components will not be shared by multiple threads
>> as they will be instantiated as one goes along or will be returned
>> from the page cache as part of a single session - and as one session
>> will be handled by only one thread, this is fine. How does concurrent
>> handling interact with stateful and stateless components?
>
> Stateful are always session specific so safe by design. Stateless are also safe, transparently, see Practical WebObjects for the details if you want.
>
>
>> Perhaps more of an issue is that code within my EOF classes may be
>> executed by more than one thread at a time. I use lazy initialisation
>> but there is a race condition there. Fortunately, most of the time
>> there are no side-effects and running that code twice would have no
>> significant deleterious effect. For situations where it would matter I
>> would assume protecting lazy initialisation with a double check and a
>> synchronised block for the inner check would be fine? Is that
>> interpretation correct?
>
> I think that synchronised is what you want.
>
>
>> Are there other commandments?
>
>
> Don't Do Stupid Things :-) Which boils down to don't share objects that are not thread-safe, or writable data, at the global level unless you have appropriate protection. Global being either static members or instance variables on your application. Shared, non-thread safe formatters are a common mistake.
>
>
> Chuck
>
>
> --
> Chuck Hill Senior Consultant / VP Development
>
> Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems.
> http://www.global-village.net/products/practical_webobjects
>
>
>
>
>
>
>
>
--
Dr. Mark Wardle
Specialist registrar, Neurology
Cardiff, UK
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