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Date: Thu, 17 Nov 2011 10:15:06 +1300
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Subject: Re: svn commit: r1158991 - in /tomcat/jk/trunk:
 native/iis/jk_isapi_plugin.c
 xdocs/miscellaneous/changelog.xml
From: Tim Whittington <timw@apache.org>
To: Tomcat Developers List <dev@tomcat.apache.org>
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OK, finally getting time to have another look at this...

https://issues.apache.org/bugzilla/show_bug.cgi?id=52191 summarises
the situation - basically the SHM filename used now is not unique
enough when there are multiple ISAPI Redirectors on a single website.
My current proposal is to use the extension_uri to distinguish between
the configurations (on the assumption that this will be the same on
every site in a web server farm).

cheers
tim

On Thu, Aug 18, 2011 at 8:08 PM, Tim Whittington <timw@apache.org> wrote:
> Yeah - not sure what I was smoking on that one.
> Have reverted for another think.
>
> The basic problem we have is that the shared memory code assumes a
> single worker configuration, and when you have multiple ISAPI
> Redirectors on a single IIS with different configs that goes a bit
> wonky. For a start, the SHM size is calculated by the first redirector
> to start (and so may be too small for the other one), and then there's
> the issue of the workers in the SHM not aligning.
>
> A possible solution might be a shm_config_name property that
> distinguishes one redirector config from another (that should be
> consistent across all processes).
> The redirector DLL path could be used instead if that was reliable - I
> don't know enough about IIS clusters to know if they span multiple
> machines.
>
> If anyone's got any other ideas I'd be interested.
>
> cheers
> tim
>
> On Thu, Aug 18, 2011 at 4:40 PM, Mladen Turk <mturk@apache.org> wrote:
>> On 08/18/2011 03:54 AM, timw@apache.org wrote:
>>>
>>> Author: timw
>>> Date: Thu Aug 18 01:54:31 2011
>>> New Revision: 1158991
>>>
>>> URL: http://svn.apache.org/viewvc?rev=1158991&view=rev
>>> Log:
>>> Use the DLL handle to make the shared memory file name used by the ISAPI
>>> Redirector unique for each DLL - the redirector supports multiple instances
>>> per website, and without this multiple redirectors could access the same
>>> shared memory file, corrupting the contents (evident when LB workers are
>>> used on IIS 7).
>>>
>>
>>
>> Hmm, isn't that actually disabling the shared memory purpose?
>> There is no point to have shared memory if it can't be shared
>> across the processes.
>>
>> Your change makes no sense to me, cause now the shared memory
>> is unique to each worker process which can be easily solved by
>> not using the shared memory at all.
>>
>> IMHO if IIS7 corrupts the shared memory, we should find a way
>> to better synchronize the access to it from multiple
>> processes instead just making it unique to each process.
>>
>>
>> Regards
>> --
>> ^TM
>>
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