[Yanel-dev] Atomic operations in Yarep

[Michael Wechner]

On 1/24/11 10:15 AM, Cedric Staub wrote:
> Hello
>
> On Fri, Jan 14, 2011 at 06:36:53PM +0100, Balz Schreier wrote:
>> do you agree that there is a potential of data inconsistency when modifying
>> a Yarep Group from within your application?
> Yes.
>
>> Scenario:
>> - The application itself can add and remove groups to a certain user,
>> depending on what that user is doing in your application.
>> - At the same time, a Yanel Administrator modifies memberships via the out
>> of the box Group Mgmt page via toolbar.
>>
>> Now, the application can remove a membership like this:
>>
>>                     group.removeMember(user); // this also removes the group
>> entry in the user XML and the user object gets saved!
>>
>>                  group.save();
>>
>> As you can see, there is no possibility that these two steps are done in 1
>> step (in Java terms: synchronized).
>> It also does not help if you write a Facade which does these two steps in a
>> synchronized way because those modifications from the yanel admin page are
>> still bypassing that facade.
> I can see how that could go wrong.
>
>> So my suggestion would be to extend Yarep by introducing this mechanism
>> built-in, so that there is no way that files can get corrupt.
>>
>> If you agree, we should work once on a patch for Yarep where such operations
>> are handled atomic.
> Sure, but then what about other scenarios? I think what we really need
> here is a facility which allows for transactions like a relational
> database has them. But implementing that will be rather difficult I
> imagine. How would you go about doing this?

maybe using

http://en.wikipedia.org/wiki/Java_Transaction_API

Just my two cents

Michael
> Cheers
> Cedric