Re: pg_basebackup, manifests and backends older than ~12

On 4/10/20 4:41 PM, Stephen Frost wrote:
> Greetings,
> 
> * David Steele (david@pgmasters.net) wrote:
>> On 4/10/20 4:09 AM, Michael Paquier wrote:
>>> I have noticed that attempting to use pg_basebackup from HEAD leads to
>>> failures when using it with backend versions from 12 and older:
>>> $ pg_basebackup -D hoge
>>> pg_basebackup: error: backup manifests are not supported by server
>>> version 12beta2
>>> pg_basebackup: removing data directory "hoge"
>>>
>>> This is a bit backwards with what we did in the past to maintain
>>> compatibility silently when possible, for example look at the handling
>>> of temporary replication slots.  Instead of an error when means to
>>> force users to have to specify --no-manifest in this case, shouldn't
>>> we silently disable the generation of the backup manifest?  We know
>>> that this option won't work on older server versions anyway.
>>
>> I'm a bit conflicted here. I see where you are coming from, but given that
>> writing a manifest is now the default I'm not sure silently skipping it is
>> ideal.
> 
> It's only the default in v13..  Surely when we connect to a v12 or
> earlier system we should just keep working and accept that we don't get
> a manifest as part of that.

Yeah, OK. It's certainly better than forcing the user to disable 
manifests, which might also disable them for v13 clusters.

-- 
-David
david@pgmasters.net