Re: [HACKERS] Restricting maximum keep segments by repslots

At Wed, 1 Mar 2017 12:17:43 -0500, Peter Eisentraut <peter.eisentraut@2ndquadrant.com> wrote in
<dc7faead-61c4-402e-a6dc-534192833d77@2ndquadrant.com>
> On 2/27/17 23:27, Petr Jelinek wrote:
> >>> WARNING:  restart LSN of replication slots is ignored by checkpoint
> >>> DETAIL:  Some replication slots lose required WAL segnents to continue.
> > However this is dangerous as logical replication slot does not consider
> > it error when too old LSN is requested so we'd continue replication,
> > hiding data loss.
> 
> In general, we would need a much more evident and strict way to discover
> when this condition is hit.  Like a "full" column in
> pg_stat_replication_slot, and refusing connections to the slot until it
> is cleared.

Anyway, if preserving WAL to replicate has priority to the
master's health, this doesn't nothing by leaving
'max_wal_keep_segments' to 0.

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center