[Koha-zebra] Updating zebradb

[Sebastian Hammer]

Hi Tümer,

We've now put some considerable time into attempting to recreate the 
problem with the updates, with no luck. It would be a great help if you 
could provide *any* additional information about what you do to cause 
this -- ideally a small test script that illustrates the problem. We've 
run 200 scripts in parallel running updates to the DB with no problem.

In particular, it would be helpful to know what the pattern of updates 
is.. do you always commit immediately as part of an update or do you 
sometimes do multiple updates between commits?

Cheers,

--Sebastian

Tümer Garip wrote:

>Hi,
>
>My hintch is that it is the multiclient usage that is causing the
>problem.
>You can have one single process doing thousands of updates one after the
>other and you do not get any problems. We already know that as when we
>first build a zebradb we do not get any problems even if we build 150K
>records as xml read from KOHA. Even if you have searches going on at he
>same time updating is blocking so the search takes a long time which is
>normal.
>
>I noticed that its actually the server crashing in the middle of an
>update if you have different processes updating the database and it is
>most probably that leaving the database in an unstable stage. I just
>realised that my zebraserver is set to automatically restart after a
>failiure. 
>
>I think rather than trying to reproduce an update/commit sequence that
>causes this crash it will be easier for you to try and use  different
>processes trying to update the database with a set of different records
>all at once and see what happens.
>
>I myself just set up a system like that and started trying. At this
>preliminary stage my findings are that server crashes and stops if you
>have multiple clients running parallel. Probably keep doing this and I
>will crash the database at some stage.
>
>Lets keep trying,
>Tumer
>
>
>
>-----Original Message-----
>From: Sebastian Hammer [mailto:quinn at indexdata.com] 
>Sent: Tuesday, March 21, 2006 6:33 PM
>To: Tümer Garip
>Cc: koha-zebra at nongnu.org
>Subject: Re: [Koha-zebra] Updating zebradb
>
>
>Tümer,
>
>Is there some sequence of updates/commits that will reliably cause the 
>crash that you've seen?
>
>If we could come up with a Perl script, say, which performed a certain 
>sequence of updates and commits and caused the problem to reappear, it 
>would be a lot easier to trace. Zebra should take care of locking 
>between commits and updates, but there might be a condition that has 
>been missed which leads to the corrupted database. Whatever it is, it 
>sounds like a bug and it's something we're keen to have fixed.
>
>I strongly suspect that the challenge here is that you have multiple 
>processes (i.e. circulation desks) doing concurrent updates..  many 
>applications I have run into would have updates funnelled through one 
>queue...  but we're pretty keen to isolate this problem.
>
>--Seb
>
>Tümer Garip wrote:
>
>  
>
>>Hi,
>>
>>This is the continuation of building zebradb thread.
>>
>>As suggested by Sebastian we moved to zebra 1.4 but our problems have 
>>not gone away. Version 1.4 not being a release version we moved back to
>>    
>>
>
>  
>
>>1.3.34 to do further tests.
>>
>>Updating zebradb with just one process is not a problem. i.e a script 
>>that reads 2000 random records modifies a flag and updates the zebradb 
>>works OK. If you do not have shadow files search respone slows down 
>>drastically but if you update with shadow files and do a single commit 
>>everything looks fine.
>>
>>But that is not a real life situation and it real life everything is 
>>still hectic. In real life you have about 20 searches going on and 
>>about 10-20 update requests in queue. In those situations zebra can not
>>    
>>
>
>  
>
>>handle things. If you use shadow files we had a crashed db. I dont know
>>    
>>
>
>  
>
>>the mechanics behind zebra but when you have:
>>
>>Update
>>|
>>|
>>|		Update
>>|		 |
>>Commit	 |
>>		 |
>>		 |
>>		commit
>>
>>Processes like this going on is it safe? Is each commit knows what to 
>>commit? I can not comment on this but just can say that it does not 
>>work.
>>
>>So we changed file handling not to use shadow files. Now we get lots of
>>    
>>
>
>  
>
>>TIMEOUT errors from updates and then zebraserver crashes. Well at least
>>    
>>
>
>  
>
>>the zebradb stayed intact.
>>
>>We tried all sorts of other things (like looping the process until it
>>updates) but all in vain.
>>
>>I can definitely say that we have not managed to get zebra updates 
>>coming from multiple clients work whatever we tried. Either ZEBRA does 
>>not like this sort of updating or we have a long way of debugging.
>>
>>A little bit disappointed but not lost hope. We'll keep on trying and 
>>reporting.
>>
>>Regards
>>Tumer
>>NEU Grand Library
>>CYPRUS
>>
>>
>>
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>>Koha-zebra at nongnu.org 
>>http://lists.nongnu.org/mailman/listinfo/koha-zebra
>>
>> 
>>
>>    
>>
>
>  
>

-- 
Sebastian Hammer, Index Data
quinn at indexdata.com   www.indexdata.com
Ph: (603) 209-6853