Subject: Re: Allow some recovery parameters to be changed with reload
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: sk@zsrv.org, a.lubennikova@postgrespro.ru, robertmhaas@gmail.com,
 michael@paquier.xyz, andres@anarazel.de, peter.eisentraut@2ndquadrant.com,
 pgsql-hackers@postgresql.org
References: <ebba1190-0336-66ef-3023-da6b1f856d82@oss.nttdata.com>
 <194171605123306@mail.yandex.ru>
 <d33c954e-a505-66bc-996e-5a92caaffbfe@oss.nttdata.com>
 <20201127.093040.1121089236433501638.horikyota.ntt@gmail.com>
From: Fujii Masao <masao.fujii@oss.nttdata.com>
Message-ID: <44876a44-60a9-c45e-15a2-5fe3239f0a09@oss.nttdata.com>
Date: Fri, 27 Nov 2020 09:48:25 +0900
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On 2020/11/27 9:30, Kyotaro Horiguchi wrote:
> At Thu, 26 Nov 2020 22:43:48 +0900, Fujii Masao <masao.fujii@oss.nttdata.com> wrote in
>>
>>
>> On 2020/11/12 4:38, Sergei Kornilov wrote:
>>> Hello
>>>
>>>> Anyway, for now I think that your first patch would be enough, i.e.,
>>>> just change the context of restore_command to PGC_SIGHUP.
>>> Glad to hear. Attached a rebased version of the original proposal.
>>
>> Thanks for rebasing the patch!
>>
>>      This parameter is required for archive recovery,
>>
>> I found the above description in config.sgml. I was just wondering
>> if it should be updated so that the actual specification is described
>> or not.
>> The actual spec is that restore_command is required to start archive
>> recovery, but optional (i.e., the parameter can be reset to an empty)
>> after archive recovery has started. But this updated version of
>> description would be rather confusing to users. So I'm now thinking
>> not to update that.
>>
>> Does anyone object to the patch? If no, I'm thinking to commit the
>> patch.
> 
> Although I don't object to make the parameter reloadable, I think it
> needs to be documented that server could stop after reloading if the
> server failed to execute the new command line.

You mean that we should document that if restore_command is set to improper command mistakenly, archive recovery may fail to restore some archived WAL files and finish without replaying those WAL? But isn't this true even without applying the patch?

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION