[Beowulf] Poll - Directory implementation

[Skylar Thompson]

Yup, indeed, nslcd is slow enough on its own that nscd helps despite its
flaws...

At this point, the only reason we haven't made the switch to sssd is that
nslcd works just well enough not to become a project to replace it.

On Sat, Oct 27, 2018 at 08:08:32AM +0100, John Hearns via Beowulf wrote:
>    To be clear I am talking about the Name Service Cacheing Daemon
>    I have always found this to be more trouble than it is worth  - it
>    holds on to out of date information,
>    and needs to be restarted when you are debugging things like batch
>    systems etc.
>    nslcd is something completely different (*)   and whoever chose similar
>    names should be forced to watch endless re-runs of the Parrot Sketch.
>    [1]https://wiki.samba.org/index.php/Nslcd
>    (*) obligatory Python reference
> 
>    On Sat, 27 Oct 2018 at 04:12, Skylar Thompson
>    <[2]skylar.thompson at gmail.com> wrote:
> 
>      Good to know - we're still nslcd users so have yet to run into that,
>      though
>      are about to make the leap to CentOS 7 where I think we will have to
>      use
>      it.
>      On Sat, Oct 27, 2018 at 03:13:47AM +0100, John Hearns via Beowulf
>      wrote:
>      >    Skylar, I believe that nscd does not work well with sssd and I
>      disabled
>      >    it.
>      >    See
>      [1][3]https://access.redhat.com/documentation/en-us/red_hat_enterpri
>      se
>      >    _linux/6/html/deployment_guide/usingnscd-sssd
>      >    I believe that nscd is the work of Auld Nick himself and causes
>      more
>      >    problems than it is worth on HPC nodes.
>      >    If you want to speed up cacheing with sssd itself you can put
>      its local
>      >    caches on a RAMdisk. This has the cost of no persistence of
>      course and
>      >    uses up RAM which you may prefer to put to better use.
>      >
>      >    On Sat, 27 Oct 2018 at 00:59, Skylar Thompson
>      >    <[2][4]skylar.thompson at gmail.com> wrote:
>      >
>      >      On Fri, Oct 26, 2018 at 08:44:28PM +0000, Ryan Novosielski
>      wrote:
>      >      > Our LDAP is very small, compared to the sorts of things
>      some
>      >      people run.
>      >      >
>      >      > We added indexes today on uid, uidNumber, and gidNumber and
>      the
>      >      problem went away. Didn’t try it earlier as it had virtually
>      no
>      >      impact on our testing system for whatever reason, but on a
>      different
>      >      testing system and on production, it dropped “ls -al /home/“
>      from
>      >      ~90s to ~5s. I’m not sure if all three were necessary, but
>      I’ll look
>      >      back at that later.
>      >      >
>      >      > We’ve run SSSD from day one, so that eliminates the nscld
>      >      question. We also moved CentOS 5.x to SSSD, FYI (I believe
>      there was
>      >      someone else with some old systems around). Was pretty
>      painless, and
>      >      SSSD eliminates a lot of problems that exist with the older
>      stuff
>      >      (including some really boneheaded very large LDAP queries
>      that were
>      >      happening routinely with the older nss-ldap software if I’m
>      >      remembering its name correctly).
>      >      Have you experimented with client-side caching services like
>      nscd?
>      >      nscd has
>      >      its quirks (in particular, it does very poorly with caching
>      spurious
>      >      negative
>      >      results from transient network failures), but it also is a
>      big
>      >      performance
>      >      improvement since you don't even have to hit the network or
>      the
>      >      directory
>      >      services.
>      >      --
>      >      Skylar
>      >      _______________________________________________
>      >      Beowulf mailing list, [3][5]Beowulf at beowulf.org sponsored by
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>      >      Computing
>      >      To change your subscription (digest mode or unsubscribe)
>      visit
>      >      [4][6]http://www.beowulf.org/mailman/listinfo/beowulf
>      >
>      > References
>      >
>      >    1.
>      [7]https://access.redhat.com/documentation/en-us/red_hat_enterprise_
>      linux/6/html/deployment_guide/usingnscd-sssd
>      >    2. mailto:[8]skylar.thompson at gmail.com
>      >    3. mailto:[9]Beowulf at beowulf.org
>      >    4. [10]http://www.beowulf.org/mailman/listinfo/beowulf
>      > _______________________________________________
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>      Computing
>      > To change your subscription (digest mode or unsubscribe) visit
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>      --
>      Skylar
>      _______________________________________________
>      Beowulf mailing list, [13]Beowulf at beowulf.org sponsored by Penguin
>      Computing
>      To change your subscription (digest mode or unsubscribe) visit
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> 
> References
> 
>    1. https://wiki.samba.org/index.php/Nslcd
>    2. mailto:skylar.thompson at gmail.com
>    3. https://access.redhat.com/documentation/en-us/red_hat_enterprise
>    4. mailto:skylar.thompson at gmail.com
>    5. mailto:Beowulf at beowulf.org
>    6. http://www.beowulf.org/mailman/listinfo/beowulf
>    7. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/deployment_guide/usingnscd-sssd
>    8. mailto:skylar.thompson at gmail.com
>    9. mailto:Beowulf at beowulf.org
>   10. http://www.beowulf.org/mailman/listinfo/beowulf
>   11. mailto:Beowulf at beowulf.org
>   12. http://www.beowulf.org/mailman/listinfo/beowulf
>   13. mailto:Beowulf at beowulf.org
>   14. http://www.beowulf.org/mailman/listinfo/beowulf

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-- 
Skylar