Re: Document recovery_target_action behavior?

On 9/28/19 12:00 PM, David Steele wrote:
> On 9/28/19 11:14 AM, Fujii Masao wrote:
>> On Sat, Sep 28, 2019 at 2:52 AM David Steele <david@pgmasters.net> wrote:
>>
>>> The question for the old versions: is this something that should be
>>> fixed in the code or in the documentation?
>>>
>>> My vote is to make this explicit in the documentation, since changing
>>> the recovery behavior in old versions could lead to nasty surprises.
>>
>> +1 to update the documentation.

FYI, documentation to compare, PG11:

https://www.postgresql.org/docs/11/recovery-target-settings.html#RECOVERY-TARGET-ACTION

PG12:

https://www.postgresql.org/docs/12/runtime-config-wal.html#RUNTIME-CONFIG-WAL-RECOVERY-TARGET

After reading through, yes, I agree that +1 we should modify the
documentation.

And +1 for not modifying the behavior in the supported PG < 12 versions,
that could certainly catch people by surprise.

>
> OK, I'll put that on my list for after GA.  This has been the behavior
> since 9.1 so it hardly seems like an emergency.
>
> The behavior change in 12 may be a surprise for users, though, perhaps
> we should add something to the Streaming Replication and Recovery
> changes section in the release notes?
>
> Looping in Jonathan to see if he thinks that's a good idea.

I would suggest we add a bullet to the "E.1.2 Migration to Version
12"[1] section as one could see this behavior change as being
"incompatible" with older versions. Moving aside the "recovery.conf"
file change, if you did not specify your "recovery_target_action" but
expect your instance to be available (albeit paused), you may be in for
a surprise, especially if you have things automated.

I don't know if I would put it in the "E.1.3.2" section though, but I
could be convinced either way.

Do you have some suggested wording? I could attempt to cobble together a
quick patch.

Thanks,

Jonathan

[1] https://www.postgresql.org/docs/12/release-12.html