Re: [HACKERS] gitlab post-mortem: pg_basebackup waiting for checkpoint

Hi,

Am Montag, den 13.02.2017, 09:31 +0100 schrieb Magnus Hagander:
> On Mon, Feb 13, 2017 at 3:29 AM, Jim Nasby <Jim.Nasby@bluetreble.com>
> wrote:
>         On 2/11/17 4:36 AM, Michael Banck wrote:
>                 I guess you're right, I've moved it further down.
>                 There is in fact a
>                 message about the xlog location (unless you switch off
>                 wal entirely),
>                 but having another one right before that mentioning
>                 the completed
>                 checkpoint sounds ok to me.
>
>         1) I don't think this should be verbose output. Having a
>         program sit there "doing nothing" for no apparent reason is
>         just horrible UI design.
>
>
> That would include much of Unix then.. For example if I run "cp" on a
> large file it sits around "doing nothing". Same if I do "tar". No?

The expectation for all three commands is that, even if there is no
output on stdout, they will write data to the local machine. So you can
easily monitor the progress of cp and tar by running du or something in
a different terminal.

With pg_basebackup, nothing is happening on the local machine until the
checkpoint on the remote is finished; while this is obvious to somebody
familiar with how basebackups work internally, it appears to be not
clear at all to some users.

So I think notifying the user that something is happening remotely while
the local process waits would be useful, but on the other hand,
pg_basebackup does not print anything unless (i) --verbose is set or
(ii) there is an error, so I think having it mention the checkpoint in
--verbose mode only is acceptable.