[basex-talk] Re: Difficult for me to understand

3 Feb 2026

      Hi Marco,

It’s just an assumption, but your problem could be related to a known xquery:fork-join bug that became effective with BaseX 12.0 and JDK  17 [1]. We are working on it, but I cannot give a timeline yet.

You can try to minimize the code that is contained in the fork-join function. For example, code like…

xquery:fork-join(
  for $i in 1 to 100
  return fn() {
    let $url := "http://xyz.com/" || $i
    return doc($url)
  }
)

…could be simplified to:

let $urls := (
  for $i in 1 to 100
  return "http://xyz.com/" || $i
)
return xquery:fork-join(
  for $url in $urls
  return fn() { doc($url) }
)

Hope this helps; please follow the referenced GitHub issue to track the progress.
Christian

[1] https://github.com/BaseXdb/basex/issues/2479
________________________________
Von: Marco Lettere via BaseX-Talk <basex-talk@mailman.uni-konstanz.de>
Gesendet: Dienstag, 3. Februar 2026 10:29
An: basex-talk@mailman.uni-konstanz.de <basex-talk@mailman.uni-konstanz.de>
Betreff: [basex-talk] Re: Difficult for me to understand

Oops, forgot to mention that meanwhile I moved from 11.7 to 12.1.

Sorry.

On 03/02/26 10:18, Marco Lettere wrote:
...
Hi Christian and all,
I'm experiencing a weird issue with a RestXQ service of mine which was
working and suddenly starts having problems because it just stops
serving requests.
I know about SSCE and so on but this time it's hard to reproduce.
Shortly, it receives about 5 simultaneous requests and for each of
those it calls one xquery:fork-join (5 functions) to query another
service.
I cannot say what the error is exactly during the time when it is
stuck. What I can see on the client are, besides HTTP 503 and Read
Timeouts, the following logs which appear frequently but with no
particular order:
ERROR: Unexpected error: java.lang.NullPointerException: Cannot invoke
"org.basex.util.hash.WeakTokenSet$WeakTokenRef.get()" because
"this.keys[index]" is null (hint:
/...y/webapp/nubisware.muscle.fiber.ccp_admin/ccp_worker_sk.xqm@65:33)
ERROR: Unexpected error: java.lang.ArrayIndexOutOfBoundsException
(hint:
/.../webapp/nubisware.muscle.fiber.ccp_admin/ccp_worker_sk.xqm@65:33)
ERROR: Unexpected error: java.lang.ArrayIndexOutOfBoundsException:
Index 8 out of bounds for length 8 (hint:
/.../webapp/nubisware.muscle.fiber.ccp_admin/ccp_worker_sk.xqm@65:33)
Line and column numbers point always to the same xquery:fork-join call.
Can you point me to what I should investigate? Am I hitting some
quantitative limit on concurrency? Connections?
Thank you for any help because I'm currently wandering in the darkness
:-)
Regards,
Marco.

[basex-talk] Re: Difficult for me to understand

Christian Grün