Subject: Re: fix "Success" error messages
To: TAKATSUKA Haruka <harukat@sraoss.co.jp>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
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 <36d38542-63e9-b73c-09fe-bd5e32e06066@2ndquadrant.com>
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 <20191121104257.a3010b3ec22f83e498147f74@sraoss.co.jp>
Cc: Michael Paquier <michael@paquier.xyz>
From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Organization: 2ndQuadrant
Message-ID: <5457fd8b-67e1-d399-b4d6-075776fed71a@2ndquadrant.com>
Date: Thu, 21 Nov 2019 10:40:36 +0100
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On 2019-11-21 02:42, TAKATSUKA Haruka wrote:
>   FATAL: could not access status of transaction ..
>   DETAIL: Could not read from file (pg_clog/.... or pg_xact/....) ...: Success.
> 
> This error has caused the server to fail to start with recovery.
> I got a report that it happend repeatedly at the newly generated
> standby cluster. I gave them advice to comfirm the low level server
> environment.
> 
> However, in addition to improving the message, should we retry to read
> the rest of the data in the case reading too few bytes?
> What about a limited number of retries instead of a complete loop?

If we thought that would help, there are probably hundreds or more other 
places where we read files that would need to be fixed up in the same 
way.  That doesn't seem reasonable.

Also, it is my understanding that short reads can in practice only 
happen if the underlying storage is having a serious problem, so 
retrying wouldn't actually help much.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services