[Mondrian] Queries being executed in serial in mondrian 3.4

[Luc Boudreau]

My guess is that dashboard B waits on some cells that are fetched by
dashboard A before rendering. As of Mondrian 3.4, we do a more efficient
cell sharing scheme; the cells are only loaded once, whereas before, two
concurrent queries could end up executing the same request if both were
issued before the cells were written to cache.

Luc

On Fri, Jun 8, 2012 at 9:31 AM, Pedro Alves <pmgalves at gmail.com> wrote:

>
> I don't think that's the case (as we actually increased that number a
> lot) but no harm done trying
>
>
> However - We just tested adding a breakpoint to a topcount def fun,
> stopping there and then opening another analysis view - It was stuck
> there until we pressed continue !!
>
>
> I'll test this in 3.3.0 or whatever was on pentaho 4.0
>
>
>
> -pedro
>
>
>
> On 06/08/2012 02:27 PM, Brian Hagan wrote:
> > Pedro,
> >
> > It does ring a bell. See http://jira.pentaho.com/browse/MONDRIAN-1080.
> Maybe you can try 3.4.3.
> >
> > - Brian
> > On Jun 8, 2012, at 9:02 AM, Pedro Alves wrote:
> >
> >>
> >>
> >> Hey there.
> >>
> >>
> >> I really don't know how to ask this. I'm not even sure there's an issue,
> >> just a set of coincidences.
> >>
> >>
> >> As most of you know, we develop a lot of dashboards that rely on mdx.
> >> Lately, we've been having a few complains that the dashboards are
> >> incredibly slow.
> >>
> >>
> >> And we can't find, in the mondrian / sql logs reasons for that to be
> slow.
> >>
> >>
> >> Until we noticed somethng weird:
> >>
> >> 1. User A accesses a dashboard that is not on cache
> >> 2. User B accesses a dashboard that should be on cache
> >> 3. We see on the logs the queries for user A
> >> 4. User B is stuck, no activity
> >> 5. User A's queries end, dashboard rendered
> >> 6. User B's dashboard is immediately rendered
> >>
> >>
> >> I saw this the first time 2 weeks ago in a mondrian over lucid. I
> >> thought it had to do with lucid's connection polling.
> >>
> >>
> >> I saw this again *today* with mondrian with mysql.
> >>
> >>
> >> Common factor: They were both on pentaho 4.5 (with mondrian 3.4.1).
> >>
> >>
> >> Commented this with Jan Aertsen and he said "weird - someone mentioned
> >> something very similar a few days ago".
> >>
> >>
> >> I'm not saying this is a regression cause I don't know what it is. I
> >> know some work has been done on query execution. But it's definitely
> >> something that was not there before (or all our dashboards would be
> >> basically unusable).
> >>
> >>
> >> Does this ring any bells to anyone? We'll try to see if we can somehow
> >> reproduce this, but it's incredibly hard to reproduce concurrency
> >> issues.... :(
> >>
> >>
> >>
> >> -pedro
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> >
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