bad logging around broken restore_command - Mailing list pgsql-hackers

From Jeff Janes
Subject bad logging around broken restore_command
Date
Msg-id CAMkU=1xkFs3Omp4JR4wMYWdam_KLuj6LXnTYfU8u3T0h=PLLMQ@mail.gmail.com
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Responses Re: bad logging around broken restore_command
Re: bad logging around broken restore_command
List pgsql-hackers
If the restore command claims to have succeeded, but fails to have created a file with the right name (due to typos or escaping or quoting issues, for example), no complaint is issued at the time, and it then fails later with a relatively uninformative error message like "could not locate required checkpoint record".

    if (rc == 0)
    {
        /*
         * command apparently succeeded, but let's make sure the file is
         * really there now and has the correct size.
         */
        if (stat(xlogpath, &stat_buf) == 0)
        {......
        }
        else
        {
            /* stat failed */
            if (errno != ENOENT)
                ereport(FATAL,
                        (errcode_for_file_access(),
                         errmsg("could not stat file \"%s\": %m",
                                xlogpath)));
        }

I don't see why ENOENT is thought to deserve the silent treatment.  It seems weird that success gets logged ("restored log file \"%s\" from archive"), but one particular type of unexpected failure does not.

I've attached a patch which emits a LOG message for ENOENT.  The exact wording doesn't matter to me, I'm sure someone can improve it.  Alternatively, perhaps the message a few lines down, "could not restore file", could get promoted from DEBUG2 to LOG when rc indicates success.  But I don't think we need any more messages which say "Something went wrong: success".

This is based on the question at https://stackoverflow.com/questions/60056597/couldnt-restore-postgres-v11-from-pg-basebackup.  But this isn' the first time I've seen similar confusion.

Cheers,

Jeff

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