Re: Avoid exception In the middle of an alloc-write

[Andy Seaborne <an...@apache.org>]

On 11/12/17 09:38, George News wrote:
> Hi,
> 
> I'm facing the exception that I include below. I guess this is because I'm not properly opening a transaction or so.
> 
> Let's try to explain a bit to guess if this is the problem:
> - I have multiple graphs which I merge using MultiUnion
> - I generate the MultiUnion in one transaction, but the use of the joined graph is done in another transaction.
> - I use a single static final Dataset from TDBFactory.createDataset(TRIPLE_STORE_PATH);
> - Read and write operations are done in different threads, so maybe we have started a join for read and in parallel we are writing on one of the graphs included in the union.
> 
> 
> Any hint is welcome.
> 
> Regards,
> Jorge
> 
> 
> org.apache.jena.tdb.base.file.FileException: In the middle of an alloc-write

This could be related to JENA-1516. Part of that, for 3.5.0, is bad 
testing of the alloc-write flag in read().

The only test case we have for this only occurs under quite high load 
with more concurrent requests than real threads in the Fuseki server.

     Andy