Re: Updated version of pg_receivexlog

On Mon, Jun 4, 2012 at 6:20 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> On Mon, Jun 4, 2012 at 11:25 PM, Ants Aasma <ants(at)cybertec(dot)at> wrote:
>> On Thu, Sep 29, 2011 at 11:30 PM, Magnus Hagander <magnus(at)hagander(dot)net> wrote:
>>>> it doesn't say that is not possible to use this for a standby
>>>> server... probably that's why i get the error i put a recovery.conf
>>>> after pg_basebackup finished... maybe we can say that  more loudly?
>>>
>>> The idea is, if you use it with -x (or --xlog), it's for taking a
>>> backup/clone, *not* for replication.
>>>
>>> If you use it without -x, then you can use it as the start of a
>>> replica, by adding a recovery.conf.
>>>
>>> But you can't do both at once, that will confuse it.
>>
>> I stumbled upon this again today. There's nothing in the docs that
>> would even hint that using -x shouldn't work to create a replica. Why
>> does it get confused and can we (easily) make it not get confused? At
>> the very least it needs a big fat warning in documentation for the -x
>> option that the resulting backup might not be usable as a standby.
>
> Unless I'm missing something, you can use pg_basebackup -x for the
> standby. If lots of WAL files are generated in the master after
> pg_basebackup -x ends and before you start the standby instance,
> you may get the following error. In this case, you need to consult with
> archived WAL files even though you specified -x option in pg_basebackup.
>
>> FATAL:  could not receive data from WAL stream: FATAL:  requested WAL
>> segment 00000001000000000000005C has already been removed
>
> Though we have the above problem, pg_basebackup -x is usable for
> the standby, I think.

I assumed from Magnus's comment that this is a known problem. I wonder
what went wrong if it should have worked. In the case where this
turned up the missing file was an xlog file with the new timeline ID
but one segment before the timeline switch. I'll have to see if I can
create a reproducible case for this.

Ants Aasma
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