Re: [Virtuoso-users] checkpointSyncMode default value

[Lorenz B. <bue...@in...>]

Hi Hugh,


I guess Jena gets no connection to the SPARQL service at the time 
Virtuoso is temporarily inaccessible

and thus simply returns a 404 error.


Cheers,

Lorenz


On 28.07.2016 15:03, Hugh Williams wrote:
> Hi Balazs,
>
>  From your stackoverflow post the “com.hp.hpl.jena.sparql.engine.http.QueryExceptionHTTP: File not found” error is coming from Jena, are any error in the Virtuoso log ? When performing a checkpoint which is an atomic action in Virtuoso the database will be temporarily inaccessible and a "40001 Error SR172: Transaction deadlocked” error or similar would be returned, thus a client application should handle such conditions as when handling deadlocks generally. Thus are any error being reported when this error occurs in Jena, in the “virtuoso.log” file ?
>
> Can you set the following params in the "[Parameters]" section of the INI file and restart the server which should enabled more detailed client errors to be returned if occurring
>
> 	CallstackOnException =  2
> 	PLDebug = 1
>
> Best Regards
> Hugh Williams
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>> On 25 Jul 2016, at 10:37, Balazs Varhegyi <var...@gm...> wrote:
>>
>> Ok, I managed to get this exception when CheckpointSynchMode is 1.
>> So when I do a query that only reads virtuoso when it does the checkpoint is  causes this com.hp.hpl.jena.sparql.engine.http.QueryExceptionHTTP, why?
>>
>> Regards, Balazs
>>
>> On 22/07/16 15:44, Balazs Varhegyi wrote:
>>> Hi,
>>>
>>> Why CheckpointSyncMode is 2 by default?
>>> What happens if we set this value to 1?
>>> I found "CheckpointSyncMode" section in this doc: http://docs.openlinksw.com/virtuoso/dbadm/
>>> but is it dangerous to set it to 1 and continue writing and reading virtuoso while it does the checkpoint?
>>> If dangerous, what can happen? if not, why it's not the default?
>>>
>>> We have an API that calls virtuoso and it gets an Exception during the checkpoint:
>>> "com.hp.hpl.jena.sparql.engine.http.QueryExceptionHTTP: File not found"
>>>
>>> Best regards,
>>> Balazs Varhegyi
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