Feedback-ID: i76984098:Fastmail
Message-ID: <d3622bf1-6a62-4703-b14e-295f47b5e348@aklaver.com>
Date: Fri, 8 Aug 2025 08:23:50 -0700
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: Questions about the continuity of WAL archiving
To: px shi <spxlyy123@gmail.com>
Cc: pgsql-general@lists.postgresql.org
References: <CAAccyYKpNsQMD+S-A7a8YtDevFN0uRXkzg4tYWWBOFsv_jASNg@mail.gmail.com>
 <fd5c6708-3791-4339-83a2-e5fc389cd9cb@aklaver.com>
 <CAAccyYLYZmwQiNMoJcQgo5t+E24rDtu1ZeBUrER7ZTKNAcZesw@mail.gmail.com>
Content-Language: en-US
From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <CAAccyYLYZmwQiNMoJcQgo5t+E24rDtu1ZeBUrER7ZTKNAcZesw@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: <https://www.postgresql.org/message-id/d3622bf1-6a62-4703-b14e-295f47b5e348%40aklaver.com>
Precedence: bulk

On 8/7/25 22:50, px shi wrote:
> Thank you for your reply.
> The archived files can be used for PITR (Point-In-Time Recovery), 
> allowing recovery to any point between WAL 80 and 100 on timeline 1.
> Additionally, if there's a backup taken during timeline 1 and a 
> switchover to a new primary has occurred without taking a new full 
> backup yet, these WAL logs can still be used to recover to any point on 
> timeline 2.

Alright I see.

Two things:

1) What is the current archiving setup on the primary and why is lagging?

2) Have you looked at archiving off the standby node while it is in 
standby per:

https://www.postgresql.org/docs/current/warm-standby.html#CONTINUOUS-ARCHIVING-IN-STANDBY

> 
> Regards,
> Pixian Shi
> 
> Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.com>> 于2025年8月8日周五 12:25写道：
> 
>     On 8/7/25 20:20, px shi wrote:
>      > Hi,
>      > There is a scenario: the current timeline of the PostgreSQL
>     primary node
>      > is 1, and the latest WAL file is 100. The standby node has also
>     received
>      > up to WAL file 100. However, the latest WAL file archived is only
>     file
>      > 80. If the primary node crashes at this point and the standby is
>      > promoted to the new primary, archiving will resume from file 100 on
>      > timeline 2. As a result, WAL files from 81 to 100 on timeline 1
>     will be
>      > missing from the archive.
> 
>     What are you planning to do with the archived files?
> 
>     Also is not the case that once the primary crashes you are in a split
>     brain case and can't really trust it's timeline anymore?
> 
> 
>      > Is there a good solution to prevent this situation?
>      >
>      > Regards,
>      > Pixian Shi
> 
> 
>     -- 
>     Adrian Klaver
>     adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com