Re: BUG #7858: Inaccurate Log Message

On Fri, Feb  8, 2013 at 06:46:29AM +0000, jackie.qq.zhang@gmail.com wrote:
> The following bug has been logged on the website:
>
> Bug reference:      7858
> Logged by:          Jackie Zhang
> Email address:      jackie.qq.zhang@gmail.com
> PostgreSQL version: 9.1.4
> Operating system:   Ubuntu
> Description:
>
> Hi,
>
> The log message of the sanity check for "superuser_reserved_connections" in
> PostmasterMain() is not accurate. See the following code snippet:
>
> /*src/backend/postmaster/postmaster.c*/
>  730         /*
>  731          * Check for invalid combinations of GUC settings.
>  732          */
>  733         if (ReservedBackends >= MaxBackends)
>  734         {
>  735                 write_stderr("%s: superuser_reserved_connections must
> be less than max_connections\n", progname);
>  736                 ExitPostmaster(1);
>  737         }
>
> The problem is that "MaxBackends" is calculated by both
> "autovacuum_max_workers" and "max_connections". See assign_maxconnections()
> and assign_autovacuum_max_workers() in src/backend/utils/misc/guc.c.
>
> The log message should inform both the two configuration parameters instead
> of only one -- the root cause could be the oversized
> "autovacuum_max_workers".

The calculation, ReservedBackends >= MaxBackends, was corrected in
Postgres 9.3 with this commit:

    commit b3055ab4fb5839a872bfe354b2b5ac31e6903ed6
    Author: Magnus Hagander <magnus@hagander.net>
    Date:   Fri Aug 10 14:49:03 2012 +0200

        Fix upper limit of superuser_reserved_connections, add limit for wal_senders

        Should be limited to the maximum number of connections excluding
        autovacuum workers, not including.

        Add similar check for max_wal_senders, which should never be higher than
        max_connections.


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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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