Re: pg_stat_progress_basebackup - progress reporting for pg_basebackup, in the server side

On 2020/02/26 23:18, Fujii Masao wrote:
>
>
> On 2020/02/18 21:31, Fujii Masao wrote:
>>
>>
>> On 2020/02/18 16:53, Amit Langote wrote:
>>> On Tue, Feb 18, 2020 at 4:42 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>>>> On 2020/02/18 16:02, Amit Langote wrote:
>>>>> I noticed that there is missing </para> tag in the documentation changes:
>>>>
>>>> Could you tell me where I should add </para> tag?
>>>>
>>>>> +     <row>
>>>>> +      <entry><literal>waiting for checkpoint to finish</literal></entry>
>>>>> +      <entry>
>>>>> +       The WAL sender process is currently performing
>>>>> +       <function>pg_start_backup</function> to set up for
>>>>> +       taking a base backup, and waiting for backup start
>>>>> +       checkpoint to finish.
>>>>> +      </entry>
>>>>> +     <row>
>>>>>
>>>>> There should be a </row> between </entry> and <row> at the end of the
>>>>> hunk shown above.
>>>>
>>>> Will fix. Thanks!
>>>
>>> Just to clarify, that's the missing </para> tag I am talking about above.
>>
>> OK, so I added </row> tag just after the above </entry>.
>>
>>>>> +  <para>
>>>>> +   Whenever <application>pg_basebackup</application> is taking a base
>>>>> +   backup, the <structname>pg_stat_progress_basebackup</structname>
>>>>> +   view will contain a row for each WAL sender process that is currently
>>>>> +   running <command>BASE_BACKUP</command> replication command
>>>>> +   and streaming the backup.
>>>>>
>>>>> I understand that you wrote "Whenever pg_basebackup is taking a
>>>>> backup...", because description of other views contains a similar
>>>>> starting line.  But, it may not only be pg_basebackup that would be
>>>>> served by this view, no?  It could be any tool that speaks Postgres'
>>>>> replication protocol and thus be able to send a BASE_BACKUP command.
>>>>> If that is correct, I would write something like "When an application
>>>>> is taking a backup" or some such without specific reference to
>>>>> pg_basebackup.  Thoughts?
>>>>
>>>> Yeah, there may be some such applications. But most users would
>>>> use pg_basebackup, so getting rid of the reference to pg_basebackup
>>>> would make the description a bit difficult-to-read. Also I can imagine
>>>> that an user of those backup applications would get to know
>>>> the progress reporting view from their documents. So I prefer
>>>> the existing one or something like "Whenever an application like
>>>>    pg_basebackup ...". Thought?
>>>
>>> Sure, "an application like pg_basebackup" sounds fine to me.
>>
>> OK, I changed the doc that way. Attached the updated version of the patch.
>
> Attached is the updated version of the patch.
>
> The previous patch used only pgstat_progress_update_param()
> even when updating multiple values. Since those updates are
> not atomic, this can cause readers of the values to see
> the intermediate states. To avoid this issue, the latest patch
> uses pgstat_progress_update_multi_param(), instead.

Attached the updated version of the patch.
Barring any objections, I plan to commit this patch.

Regards,

--
Fujii Masao
NTT DATA CORPORATION
Advanced Platform Technology Group
Research and Development Headquarters