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From "Walker, Andreas" <andreas.wal...@sub.uni-goettingen.de>
Subject AW: AW: AW: Error 500: No conversion to a Node: <RDF_Term >
Date Mon, 11 Mar 2019 14:37:00 GMT
Hi Andy,


the database was created from the web interface, and I've only used the web interface to add
data to it, so no other version has ever touched it.


If I understand you correctly, the problem is with the database as a whole, so dropping and
reloading the graph might not solve the problem. I have now switched to a fresh database and
am currently reloading the data, so I can see whether the problem persists beyond the original
database.


The only backup I have done is by making snapshots of the entire virtual server this is running
on, so I don't think that is related in any way.


Thanks again for your help,

Andreas

________________________________
Von: Andy Seaborne <andy@apache.org>
Gesendet: Freitag, 8. März 2019 10:50:28
An: users@jena.apache.org
Betreff: Re: AW: AW: Error 500: No conversion to a Node: <RDF_Term >

Hi Andreas,

Is this a database that has only ever been used with 3.10.0 or was the
data loaded with a previous version at some time in the past?

The problem occurs silently during loading. There is no sign of the
problem at the time and the system works just fine while the RDF term,
or terms, are also in the node table cache.

Then the system is restarted.

Then the RDF term is needed for a query and the errors are reported.

But the problem originated back when the data was loaded or updated, may
be several restarts ago.

Of course, it may be a different issue in which case, but the error
message is consistent with the known bug.

Have you been backing up the server on a regular basis? A backup is
NQuads so it is pulling every RDF term from disk (subject to already
being cached).

     Andy

On 07/03/2019 20:47, Walker, Andreas wrote:
> Hi Andy,
>
>
> I am running Version 3.10.0. The problem with reloading the database is the regular (multiple
times a day) recurrence of the problem, so if there are any strategies to avoid it, I'd appreciate
any advice.
>
>
> Best,
>
> Andreas
>
>
> ________________________________
> Von: Andy Seaborne <andy@apache.org>
> Gesendet: Donnerstag, 7. März 2019 21:12
> An: users@jena.apache.org
> Betreff: Re: AW: Error 500: No conversion to a Node: <RDF_Term >
>
> Hi Andreas - which version are you running?
>
> It does not look like the  corruption problem, which is now fixed.
>
> The best thing to do is reload the database again. Whatever terms were
> messed up are permanently damaged I'm afraid.
>
>       Andy
>
> On 07/03/2019 10:49, Walker, Andreas wrote:
>> Dear all,
>>
>>
>> as a quick follow-up which might be helpful in identifying the error; I can currently
run a SPARQL query (just listing any triples) with LIMIT 80, but no higher, before I run into
the error, so it seems like there might indeed be a particular part of the database that is
corrupted.
>>
>>
>> Best,
>>
>> Andreas
>>
>> ________________________________
>> Von: Walker, Andreas <andreas.walker@sub.uni-goettingen.de>
>> Gesendet: Mittwoch, 6. März 2019 10:42:32
>> An: users@jena.apache.org
>> Betreff: Error 500: No conversion to a Node: <RDF_Term >
>>
>> Dear all,
>>
>>
>> from time to time, my Fuseki server starts throwing the following error message on
any SPARQL query I pose to one of my graphs:
>>
>>
>> "Error 500: No conversion to a Node: <RDF_Term >"
>>
>>
>> Unfortunately, I couldn't find any explanation of this error message, beyond a discussion
of a corrupted TDB2 database.
>>
>>
>> (https://users.jena.apache.narkive.com/LF4XE801/corrupted-tdb2-database)<https://users.jena.apache.narkive.com/LF4XE801/corrupted-tdb2-database>
>>
>>
>> Once this happens, the only thing I could do so far is to drop the entire afflicted
graph and rebuild it, but of course that isn't going to be a viable solution in the long term.
>>
>>
>> The only way I interact with Fuseki is by starting and stopping it, querying it via
the SPARQL endpoint (and sometimes through the web interface, e.g. when troubleshooting my
application), and uploading new triples (as turtle files) via the web interface. I haven't
been able to find a pattern in when the error appears so far.
>>
>>
>> Any insights into why this error appears, and what to do in order to avoid it? I'd
appreciate any help.
>>
>>
>> Best,
>>
>> Andreas
>>
>

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