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Posted to users@jena.apache.org by Dimitris Spanos <di...@gmail.com> on 2020/12/27 14:08:09 UTC
Is there a dataset registry in ARQ or Jena?
Hi all,
I was wondering if there is a registry in ARQ or Jena base that keeps track
of all registered datasets?
Such a registry would be helpful, since I have a custom
Dataset/DatasetGraph implementation and I would like to perform some
resource cleanup during JenaSubsystemLifecycle.stop() for every dataset.
I am aware of DataAccessPointRegistry but from an architectural point of
view, I would not want my Jena submodule to depend on Fuseki.
Right now, I have implemented a Singleton dataset registry for my custom
datasets (registration happens during dataset assembly), but I am curious
to know if there is another/better way to retrieve registered datasets.
Regards,
Dimitris
Re: Is there a dataset registry in ARQ or Jena?
Posted by Andy Seaborne <an...@apache.org>.
On 27/12/2020 17:48, Dimitris Spanos wrote:
> Hi Andy,
>
> Thanks for your answer. The dataset cleanup operation I am referring to is
> just closing a database pool.
>
> Given that my custom dataset is read-only, after an abnormal server
> shutdown, I would expect no dataset recovery actions are needed and the
> only impact would be a few open connection pools.
>
> Despite that the latter cannot be avoided, I think it's still beneficial to
> try to handle graceful shutdown by closing the open pools.
Agreed - more friendly for an external resource that timeouts eventually.
As long as you're not assuming the dataset will have shutdown code
called because sometimes it won't!
Andy
>
> On Sun, Dec 27, 2020 at 7:18 PM Andy Seaborne <an...@apache.org> wrote:
>
>> Hi Dimitris,
>>
>> On 27/12/2020 14:08, Dimitris Spanos wrote:
>>> Hi all,
>>>
>>> I was wondering if there is a registry in ARQ or Jena base that keeps
>> track
>>> of all registered datasets?
>>
>> There isn't.
>>
>>> Such a registry would be helpful, since I have a custom
>>> Dataset/DatasetGraph implementation and I would like to perform some
>>> resource cleanup during JenaSubsystemLifecycle.stop() for every dataset.
>>> I am aware of DataAccessPointRegistry but from an architectural point of
>>> view, I would not want my Jena submodule to depend on Fuseki.
>>
>> Any dataset implementation has to survive reality.:-)
>>
>> Reality includes (machine|process|JVM) crashes, "kill -9" and
>> System.exit(0) and nasty things in transactions like out of disk space.
>>
>> Datasets have to cope with unexpected stops. For example, when a TDB(1
>> or 2) dataset starts, it check whether any recovery actions are needed
>> and does them as it starts,
>>
>> Because that happens, clean shutdown can only be an "extra". Once you
>> trust the recovery, adding clean shutdown is extra work.
>>
>> What sort of clean shutdown does you dataset impl wish to do?
>>
>> Andy
>>
>>> Right now, I have implemented a Singleton dataset registry for my custom
>>> datasets (registration happens during dataset assembly), but I am curious
>>> to know if there is another/better way to retrieve registered datasets.
>>>
>>> Regards,
>>> Dimitris
>>>
>>
>
Re: Is there a dataset registry in ARQ or Jena?
Posted by Dimitris Spanos <di...@gmail.com>.
Hi Andy,
Thanks for your answer. The dataset cleanup operation I am referring to is
just closing a database pool.
Given that my custom dataset is read-only, after an abnormal server
shutdown, I would expect no dataset recovery actions are needed and the
only impact would be a few open connection pools.
Despite that the latter cannot be avoided, I think it's still beneficial to
try to handle graceful shutdown by closing the open pools.
On Sun, Dec 27, 2020 at 7:18 PM Andy Seaborne <an...@apache.org> wrote:
> Hi Dimitris,
>
> On 27/12/2020 14:08, Dimitris Spanos wrote:
> > Hi all,
> >
> > I was wondering if there is a registry in ARQ or Jena base that keeps
> track
> > of all registered datasets?
>
> There isn't.
>
> > Such a registry would be helpful, since I have a custom
> > Dataset/DatasetGraph implementation and I would like to perform some
> > resource cleanup during JenaSubsystemLifecycle.stop() for every dataset.
> > I am aware of DataAccessPointRegistry but from an architectural point of
> > view, I would not want my Jena submodule to depend on Fuseki.
>
> Any dataset implementation has to survive reality.:-)
>
> Reality includes (machine|process|JVM) crashes, "kill -9" and
> System.exit(0) and nasty things in transactions like out of disk space.
>
> Datasets have to cope with unexpected stops. For example, when a TDB(1
> or 2) dataset starts, it check whether any recovery actions are needed
> and does them as it starts,
>
> Because that happens, clean shutdown can only be an "extra". Once you
> trust the recovery, adding clean shutdown is extra work.
>
> What sort of clean shutdown does you dataset impl wish to do?
>
> Andy
>
> > Right now, I have implemented a Singleton dataset registry for my custom
> > datasets (registration happens during dataset assembly), but I am curious
> > to know if there is another/better way to retrieve registered datasets.
> >
> > Regards,
> > Dimitris
> >
>
Re: Is there a dataset registry in ARQ or Jena?
Posted by Andy Seaborne <an...@apache.org>.
Hi Dimitris,
On 27/12/2020 14:08, Dimitris Spanos wrote:
> Hi all,
>
> I was wondering if there is a registry in ARQ or Jena base that keeps track
> of all registered datasets?
There isn't.
> Such a registry would be helpful, since I have a custom
> Dataset/DatasetGraph implementation and I would like to perform some
> resource cleanup during JenaSubsystemLifecycle.stop() for every dataset.
> I am aware of DataAccessPointRegistry but from an architectural point of
> view, I would not want my Jena submodule to depend on Fuseki.
Any dataset implementation has to survive reality.:-)
Reality includes (machine|process|JVM) crashes, "kill -9" and
System.exit(0) and nasty things in transactions like out of disk space.
Datasets have to cope with unexpected stops. For example, when a TDB(1
or 2) dataset starts, it check whether any recovery actions are needed
and does them as it starts,
Because that happens, clean shutdown can only be an "extra". Once you
trust the recovery, adding clean shutdown is extra work.
What sort of clean shutdown does you dataset impl wish to do?
Andy
> Right now, I have implemented a Singleton dataset registry for my custom
> datasets (registration happens during dataset assembly), but I am curious
> to know if there is another/better way to retrieve registered datasets.
>
> Regards,
> Dimitris
>