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Date: Fri, 1 Mar 2013 12:47:23 +0000
From: =?ISO-8859-1?Q?Michael_D=FCrig?= <mduerig@apache.org>
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To: <oak-dev@jackrabbit.apache.org>
Subject: Re: Behaviour of Move Operations
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What Jukka is saying is that the repository gives you a choice between 
consistency and availability. Since both you cannot have.

Michael

On 1.3.13 12:40, Felix Meschberger wrote:
> So you essentially say: Behaviour of the repository is "best effort" and we -- at the  end of the day -- cannot trust the repository ?
>
> Sounds frightening.
>
> IMHO the repository should be failsafe and thus eventually solve the issue making sure we don't end up with two copies of the same node (actually both copies, if referenceable, will even have the same node ID....
>
> Regards
> Felix
>
> Am 27.02.2013 um 16:35 schrieb Jukka Zitting:
>
>> Hi,
>>
>> On Wed, Feb 27, 2013 at 5:09 PM, Carsten Ziegeler <cziegeler@apache.org> wrote:
>>> How will this be handled with Oak? Could it happen that due to this
>>> happening concurrently that the node ends up twice in the repository
>>> (at /1/node and /2/node in my example)?
>>
>> The behavior depends on the underlying MicroKernel implementation.
>>
>> With the new SegmentMK I've been working on, you can control the behavior:
>>
>> * If both cluster nodes use the same (root) journal, then only one of
>> them succeeds and the other one will fail with an exception. The
>> behavior is more or less the same as with current Jackrabbit.
>>
>> * If the cluster nodes use different journals (with background
>> merging), then one of the moves will succeed and depending on timing
>> the other one either fails or ends up producing a duplicate copy of
>> the tree.
>>
>> The latter option is designed to boost write concurrency in scenarios
>> where it's OK for some operations to get lost or produce somewhat
>> inconsistent results (high-volume commenting or logging systems,
>> etc.). Operations for which such behavior is not desirable should use
>> the first option.
>>
>> BR,
>>
>> Jukka Zitting
>
>
> --
> Felix Meschberger | Principal Scientist | Adobe
>
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