Ok, I'll do that! :-D
Andrus Adamchik escribió:
> It's not that expensive (each context attaches to a shared stack) and
> looks like the best strategy in your case.
>
> One possible optimization is to use a single shared DataContext for
> read-only operations, and create a new DataContext for each operation
> that is expected to modify and commit the objects. It is only possible
> of course if you have any "read-only" operations at all.
>
> Andrus
>
>
> On Jan 7, 2008, at 5:30 PM, Álvaro Martínez wrote:
>
>>
>> Thanks, Andrus and Philip
>>
>> The threads I'm talking about are created from many sources and for
>> different reasons. Not of all them are triggered in response to
>> "something". There are also watchers, periodic tasks... So I can't
>> map data contexts to some particular condition.
>>
>> So then I have to create one data context per operation (that means a
>> set of actions). Is this expensive? We are developing a heavy loaded
>> cluster of servers, so it's important.
>>
>> Thanks again!
>>
>>
>> Andrus Adamchik escribió:
>>> Hi Álvaro,
>>>
>>> It is hard to give a precise advice on multithreading without
>>> knowing the nature of your application. So here is a few general notes:
>>>
>>> * DataContext instance is your isolated area for making in-memory
>>> changes to objects that will all be committed at once. So consider
>>> using multiple contexts as appropriate. Cayenne docs recommend
>>> various common patterns, such as DataContext per session (i.e. each
>>> user has a dedicated context), DataContext per request, or
>>> DataContext per application (in a read-only app). You can also
>>> devise your own approach, if none of the above fit your needs. All
>>> you need to know here is that multiple threads *reading* from a
>>> shared DataContext is ok, but multiple threads *writing* to a shared
>>> DataContext is not ok.
>>>
>>> * In a rare case if you really need multiple threads to work off of
>>> the same context, consider using a dedicated nested DataContext for
>>> each atomic object modifications.
>>>
>>> Andrus
>>>
>>>
>>> On Jan 7, 2008, at 2:44 PM, Álvaro Martínez wrote:
>>>>
>>>> Hi, I've been working for a while with Cayenne but never realized I
>>>> had a problem... until I got a weird exception.
>>>>
>>>> The fact is that I had been using context.newObject() and
>>>> context.commitChanges() to create new rows in the database. But my
>>>> application works with many threads, so global commits can (and in
>>>> fact do) interrupt normal creation of objects. Thread A and Thread
>>>> B are creating objects and filling their fields, but then B commits
>>>> all and A throws a validation exception because mandatory fields
>>>> are missing.
>>>>
>>>> How could I commit only one object?
>>>>
>>>> Thanks,
>>>>
>>>> Álvaro from Spain (Push the button Inc.)
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>
>
>
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