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Re: poor ldap load distribution

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  • Dan Lannom
    ... I m using virtual(5) and relay_recipients which is set to $virtual_alias_maps. ... I ll try out proxymap. I ve always considered our email environment
    Message 1 of 4 , Jun 1, 2007
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      Victor Duchovni wrote:
      > On Fri, Jun 01, 2007 at 02:14:34PM -0400, Dan Lannom wrote:
      >
      >> I'm trying to use a round robin DNS entry to distribute the queries over
      >> multiple ldap servers, but for some reason they are all being redirected
      >> to the same system, which is pushing load too high.
      >>
      >
      > In what Postfix context are you using LDAP? Are you using "proxy:ldap:..."?
      > Is transport(5) lookups?

      I'm using virtual(5) and relay_recipients which is set to
      $virtual_alias_maps.

      >
      > - Most people who care about load, have high volume systems, where
      > proxymap(8) is a must for LDAP queries from smtpd(8) and cleanup(8),
      > so the picture changes. Each proxymap(8) process (many fewer of
      > these) connects to an LDAP server and stays connected. These connection
      > count is one or two orders of magnitude lower, but distribution may
      > be uneven, and stay uneven, if you roll "heads" a few times in a row.

      I'll try out proxymap. I've always considered our email environment
      small since we're only accepting ~200k messages per day

      I'm typically seeing 60-120 established LDAP sessions all to the same
      host, so its more than a few bad rolls.

      > On my "busy" server using LDAP via proxymap for virtual(5) rewrites, the
      > process counts (sampled just now) are:
      >
      > 76 smtpd
      > 21 cleanup
      > 7 proxymap
      >
      > so 97 would-be LDAP clients are served by 7 LDAP connections from
      > 7 proxymap processes, which if LDAP cooperates each pick their
      > own IP address for the LDAP server.
      >
      > I don't actually use multiple A records for LDAP load balancing, rather
      > for machines in a cluster, I shuffle the LDAP server preference list from
      > host to host, and in some cases use actual network load balancers.

      I'll switch to the shuffle method, I was probably trying to do too much
      with DNS.

      Thanks,

      Dan
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