[Qitab-devel] A problem of quux-hunchentoot and its solution

[昊 谢]

Hi fahree,

It works on my OSX 10.9.2, sbcl 1.1.17, and hunchentoot 1.2.26. Although I haven’t tested it on the other environments, I think it should be.

Thank you.

On Apr 25, 2014, at 18:11 , Faré <fahree at gmail.com> wrote:

> Dear xiehao,
> 
> thank you for excellently diagnosing this issue.
> I have pushed a fix that I think is more robust,
> but it is wholly untested, so please tell me if it works for you.
> 
> —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org
> My hobby of not attending meetings about recycling saves more energy than
> your hobby of recycling.  — John McCarthy
> 
> 
> On Thu, Apr 24, 2014 at 11:03 PM, 昊 谢 <xiehao at outlook.com> wrote:
>> + qitab-devel
>> 
>> On Apr 25, 2014, at 15:00 , 昊 谢 <xiehao at outlook.com> wrote:
>> 
>> HI Francois-Rene Rideau, qitab-devel,
>> 
>> I encountered a problem when I’m using your quux-hunchentoot and I have a
>> simple way to fix it. Could you please consider it?
>> 
>> When I’m using the thread-pooling taskmaster and starting acceptor, there
>> may be an error invoked occasionally like this:
>> debugger invoked on a SIMPLE-ERROR in thread
>> #<THREAD "quux-hunchentoot-dispatcher-*:8080" RUNNING {10035DDF03}>:
>>  The assertion
>>  (EQ QUUX-HUNCHENTOOT::DISPATCHER-PROCESS
>> (BORDEAUX-THREADS:CURRENT-THREAD))
>>  failed with QUUX-HUNCHENTOOT::DISPATCHER-PROCESS = NIL,
>>  (BORDEAUX-THREADS:CURRENT-THREAD) =
>>  #<SB-THREAD:THREAD "quux-hunchentoot-dispatcher-*:8080" RUNNING
>> {10035DDF03}>.
>> 
>> I think the reason for this is quite straightforward. While the method
>> “execute-acceptor” is creating dispatcher thread and set it by the
>> dispatcher-process accessor of taskmaster, we can’t imagine the “setf”
>> action comes first. In other words, if dispatcher thread started before the
>> accessor was set, the assertion in ensure-dispatcher-process may fail.
>> 
>> My solution for this is quite simple and here’s the effective solution,
>> adding something like a spin-lock.
>> diff --git a/thread-pooling.lisp b/thread-pooling.lisp
>> index dcb3427..8f3f32b 100644
>> --- a/thread-pooling.lisp
>> +++ b/thread-pooling.lisp
>> @@ -146,6 +146,7 @@ then the reply will be HTTP 503."))
>> 
>> (defmethod ensure-dispatcher-process ((taskmaster
>> thread-pooling-taskmaster))
>>   (with-taskmaster-accessors (dispatcher-process) taskmaster
>> +    (do () (dispatcher-process) (sleep 0.1))
>>     (assert (eq dispatcher-process (bt:current-thread)))))
>> 
>> (defmethod decrement-taskmaster-accept-count ((taskmaster
>> thread-pooling-taskmaster))
>> 
>> Maybe you can get a better patch to solve this problem and I’m looking
>> forward your reply.
>> 
>> Thanks & have a good day
>> Hao Xie
>> 
>