Sorry, missed this question ...
It depends on the scale of the data, the size of the tomcat application,
the machine sizes available and how much API-side in-memory caching you
want to do.
We use both styles successfully. For modest data even at high load, or
for large data at modest load then having both on the same machine works
fine and is slightly easier to scale out. So long as your machines have
a reasonable memory footprint for the data scale. For larger data
(300-400MT plus) with either significant query rates or very memory
hungry applications we split the data and front end tiers.
Dave
On 19/09/17 20:02, Dimov, Stefan wrote:
Thanks for the response!
One more question:
Would it be better if I put Tomcat on one machine and have Fuseki on another?
Provided they are both in the same network and the connection between them is
unobstructed, wouldn’t this improve the performance, considering they don’t
share memory/CPU?
Regards,
Stefan
On 9/19/17, 5:24 AM, "Dave Reynolds" <[email protected]> wrote:
On 19/09/17 11:33, George News wrote:
>
> On 2017-09-19 09:57, Dave Reynolds wrote:
>> On 19/09/17 01:13, Dimov, Stefan wrote:
>>> Hi,
>>>
>>> I have Tomcat setup, that receives REST requests, “translates” them
>>> into SAPRQL queries, invokes them on the underlying FUSEKI and returns
>>> the results:
>>>
>>>
>>> USER AGENT
>>> ^
>>> REST
>>> v
>>> ---------------
>>> TOMCAT
>>> ^
>>> REST
>>> v
>>> -------------
>>> FUSEKI
>>> ------------
>>> JENA
>>> -----------
>>> TDB
>>> ----------
>>>
>>> Would I be able to achieve significant performance improvement, if I
>>> use directly the JENA libraries and bypass FUSEKI?
>>
>> Unlikely. We successfully use the set up you describe for dozens of
>> services, some quite high load. We have a few which go direct to Jena
>> for legacy reasons and they show no particular performance benefits.
>>
>> If your payloads can be large then make sure the way you are driving
>> fuseki is streaming and doesn't accidentally store the entire SPARQL
>> results in your tomcat app. This also means chosing a streamable media
>> type for your fuseki requests.
>
> I'm using Jena to create my own REST service and I'm facing some issues
> when SPARQL resultsets are big. Could you please give me a hint on the
> streaming stuff from fuseki so I can incorporate that to my REST service?
If you are just doing SELECTs then it should be straightforward. Of the
sparql results media types then at least XML and TSV are streaming. We
just use Jena's QueryExecutionFactory.sparqlService in the REST service
to set up the execution. We wrap the ResultSet from execSelect and
process that one row at a time. Our wrapper keeps track of the
underlying QueryExecution so we can close that when finished or in the
event of a problem.
For DESCRIBE/CONSTRUCT queries then use a streamable media type for the
RDF such as ntriples/nquads. We have less experience of that, we tend to
actually execute those in batches (a SELECT provides a set of resource
bindings and we then issue a DESCRIBE on those resources one batch at a
time).
Dave
