[Koha] when will koha master work with elastic search 5.X

[David Holoshka]

Nau Mai,

I am working with migrating an vtls ILS to koha for a uni library.  
Mostly I have been recoding and optimizing some old bywater scripts and 
some koha import utilities  to import our 3.2 M+ holdings into koha.

We are trying to run koha master with elastic search due to performance 
issues with zebra.  Our initial impression was that koha worked with ES 
5.X so we installed 5.3, but we can not get it to work at all with 
authorities.  The indexing processes generates a 7 Gbyte file filled 
with warnings and several key fields in elastic search contain nulls.   
It is possible to perform some searches on the biblio index if the sort 
is turned off, but it does not seem to work fully either.

We have been studying bugzilla to try and figure out what is supposed to 
work.  I have tried to apply several new patches to koha ES with out 
seeing any improvement.

My questions are :

1/  Can koha be made to work with elastic search 5.X  ?

2/  If not are when will Koha work with ES 5.x ?

3/  Does some version of Koha work with an older version of ES ?

Best Regards,

Dave