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Re: [Exist-open] Urgent assistance with locking behaviour of existdb / deadlocking
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From: Pieter L. <pie...@be...> - 2025-10-15 12:09:14
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I don't know how to get that dump, would that be with jstack {pid} >
C:\jstack.txt? I am not too keen on breaking my instance as I have a lot
to do with it. Also, exist completely freezes so I do not know whether
it would be possible to extract anything.
-p
On 10/15/2025 1:55 PM, Adam Retter wrote:
> Would it be possible to see a dump of the lock table when that happens
> Pieter?
>
> On Wed, 15 Oct 2025 at 12:52, Pieter Lamers via Exist-open
> <exi...@li...> wrote:
>
> Hi Adam,
>
> It is not trivial to create a reproduceable case for the
> deadlocking problem but I am seeing deadlocks all the time when I
> do not take the necessary precautions when updating. I think it
> has to do with module imports. I think the deadlock occurs when
> the update of a library module is attempted which is also holding
> a read-lock because of an active process. Or the other way around:
> you make a request which involves a library which is being
> updated. At least one of these scenarios and maybe both can break
> my setup.
>
> This does not seem to be Willem's problem tho.
>
> Best,
> Pieter
>
> On 10/14/2025 9:59 AM, Adam Retter wrote:
>>
>> Hi Willem,
>>
>> In eXist-db 5.x.x and 6.x.x, the XQuery (if stored in the
>> database) is treated as any other document, and so it is locked
>> for the duration of operations that happen upon it. Unfortunately
>> this means that whilst a query is executing the document holding
>> that query will keep a READ lock on the document.
>>
>> A document may have many either a single write lock, or one or
>> more read locks. This means that the query can only be updated by
>> one person/client at a time, but that multiple clients can run
>> the query in parallel.
>>
>> I am not sure how a deadlock could occur with this. Can you
>> provide some further information about your issue, and how to
>> reproduce it please?
>>
>> Thanks, Adam.
>>
>> On Tue, 14 Oct 2025 at 08:53, Willem van der Westhuizen
>> <wi...@kw...> wrote:
>>
>> Hi
>>
>> We use existdb extensively to run xqueries on our external
>> databases,
>> couchdb and others. We dont use the existdb datastore for our
>> data.
>>
>> We used to run on an old 3.3.3 version of existdb, and
>> recently migrated
>> to 6.2. Since then we have found that existdb locks the
>> xquery that is
>> being executed, causing deadlocks that eventually locks up
>> the server.
>> Is there an easy way to tell existdb to revert to the older
>> locking
>> behaviour that does not lock up the xquery being run?
>>
>>
>> Regards
>>
>> --
>> Willem van der Westhuizen
>> +27 82 9200718
>>
>>
>>
>> _______________________________________________
>> Exist-open mailing list
>> Exi...@li...
>> https://lists.sourceforge.net/lists/listinfo/exist-open
>>
>>
>>
>> --
>> Adam Retter
>>
>> eXist Core Developer
>> { United Kingdom }
>> ad...@ex...
>>
>>
>> _______________________________________________
>> Exist-open mailing list
>> Exi...@li...
>> https://lists.sourceforge.net/lists/listinfo/exist-open
>
> --
> Pieter Lamers
> John Benjamins Publishing Company
> Postal Address: P.O. Box 36224, 1020 ME AMSTERDAM, The Netherlands
> Visiting Address: Klaprozenweg 75G, 1033 NN AMSTERDAM, The Netherlands
> Warehouse: Kelvinstraat 11-13, 1446 TK PURMEREND, The Netherlands
> tel: +31 20 630 4747
> web:www.benjamins.com <http://www.benjamins.com>
>
>
> _______________________________________________
> Exist-open mailing list
> Exi...@li...
> https://lists.sourceforge.net/lists/listinfo/exist-open
>
>
>
> --
> Adam Retter
>
> eXist Core Developer
> { United Kingdom }
> ad...@ex...
--
Pieter Lamers
John Benjamins Publishing Company
Postal Address: P.O. Box 36224, 1020 ME AMSTERDAM, The Netherlands
Visiting Address: Klaprozenweg 75G, 1033 NN AMSTERDAM, The Netherlands
Warehouse: Kelvinstraat 11-13, 1446 TK PURMEREND, The Netherlands
tel: +31 20 630 4747
web:www.benjamins.com
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