Re: The function of lock file named ".s.PGSQL..lock" on Linux?

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От Tom Lane
Тема Re: The function of lock file named ".s.PGSQL..lock" on Linux?
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Msg-id 23168.1281488995@sss.pgh.pa.us
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Ответ на Re: The function of lock file named ".s.PGSQL..lock" on Linux?  (Greg Smith <greg@2ndquadrant.com>)
Ответы Re: The function of lock file named ".s.PGSQL..lock" on Linux?  (Tom Lane <tgl@sss.pgh.pa.us>)
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Greg Smith <greg@2ndquadrant.com> writes:
> Tom Lane wrote:
>> We can't portably lock the socket file itself, so we make a separate
>> ordinary file for locking purposes.

> It looks to me like the fact that the .lock file is created is only
> documented in src/backend/utils/init/miscinit.c , and even there the
> reason why (what you wrote above) isn't mentioned.  Seems like noting
> this file is created in the unix_socket_directory entry of the docs, and
> the rationale for why in the source code, would make a useful
> improvement.  Anybody want to write a little documentation patch?

FWIW, the discussion about that was here:
http://archives.postgresql.org/pgsql-hackers/2000-11/msg01306.php

and the subsequent commit was

2000-11-29 15:59  tgl

    * configure, configure.in, src/backend/libpq/pqcomm.c,
    src/backend/postmaster/postmaster.c, src/backend/tcop/postgres.c,
    src/backend/utils/init/miscinit.c, src/backend/utils/misc/guc.c,
    src/bin/pg_ctl/pg_ctl.sh, src/include/config.h.in,
    src/include/miscadmin.h: Get rid of not-very-portable
    fcntl(F_SETLK) mechanism for locking the Unix socket file, in favor
    of having an ordinary lockfile beside the socket file.    Clean up a
    few robustness problems in the lockfile code.  If postmaster is
    going to reject a connection request based on database state, it
    will now tell you so before authentication exchange not after.    (Of
    course, a failure after is still possible if conditions change
    meanwhile, but this makes life easier for a yet-to-be-written
    pg_ping utility.)

(The pgsql-committers messages were pretty useless back then, so I won't
point you to that archive.)

            regards, tom lane

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