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From Ian Boston <...@tfd.co.uk>
Subject Re: Concurrent Use of System Session in ACLProvider Question.
Date Mon, 04 Oct 2010 08:05:28 GMT

On 3 Oct 2010, at 13:16, Jukka Zitting wrote:

> Hi,
> 
> On Sun, Oct 3, 2010 at 12:51 PM, Ian Boston <ieb@tfd.co.uk> wrote:
>>  Just in case it helps, I have commented and attached patches for the partial
>> solution that I am working on which eliminate blocking by simply not sharing
>> the SystemSession in the AccessControlProvider.
> 
> Excellent, thanks!
> 
> BR,
> 
> Jukka Zitting


For posterity:
One other fix mentioned on the jira was to remove synchronisation from the cache surrounding
the LRUMap in the AbrstractPrincipalProvider, and protect the operation from failure with
try {} catch {} (LRUMap throws NPE on concurrent access). 

This has now freed our code base up to the extent that read concurrency is being limited by
the SharedItemManager, however we still are limited to around 1000 requests per second regardless
of number of cores, indicating although faster, its still single threaded. What I don't know
is if being fast but single threaded is good enough to support the number of users we have
to support per JVM.

Jukka, 
Do you think your work on JCR-2699 will make reads truly concurrent with no blocking or will
there always be a part of the code base that is essentially single threaded? 
I ask because this might become a deal breaker for us, and I would rather not raise expectations,
or ask too for too much from the Jackrabbit community, if our usage of Jackrabbit  is not
going to match the aims of Jackrabbit.

Thanks
Ian
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