I thought as much. The basic problem, however, is that I never created the logical slots. The IIDR application did that
allby itself, and after it terminated, it did not bother to remove the slots. So, my disk monitor threw up when the WAL
filesystem began to fill up. I was trying then to figure out why it did that.
Sent from my iPhone
> On Feb 27, 2019, at 7:57 AM, Achilleas Mantzios <achill@matrix.gatewaynet.com> wrote:
>
>> On 27/2/19 2:52 μ.μ., Johannes Truschnigg wrote:
>> Hi Jay,
>>
>>> On Wed, Feb 27, 2019 at 07:40:26AM -0500, John Scalia wrote:
>>> Hello, folks,
>>>
>>> Yesterday, I had a small file system fill up, due to some logical
>>> replication testing we had been performing. We had been testing IBM’s IIDR
>>> system and apparently it had built a logical replication slot on my server.
>>> When the test was completed, nobody removed the slot, so WAL segments
>>> stopped being dropped. Now I can understand the difficulty separating what
>>> physical versus logical replication needs from the WAL segments, but as
>>> logical replication is database specific not cluster wide, this behavior was
>>> a little unexpected, since the WAL segments are cluster wide. Are WAL
>>> segments going to pile up whenever something drops a logical replication
>>> connection? I’ve seen it, but it seems like this could be a bad thing.
>> Since Logical Replication is piggybacked on Physical Replication, you cannot
>> use the first without having the latter. And yes, what you experienced is one
>> of the dangers of using replication slots when having a busy database (i.e.
>> producing lots of WAL) and a filesystem with little excess space. Under these
>> circumstances, it is imperative to monitor for (and alert on) anything going
>> awry with your replication slot consumers, and/or the size of your wal/xlog
>> directory. It's a feature of replication slots to work that way - but one that
>> may end up biting you.
> A logical approach for replication slots would be to accept a parameter regarding max WAL files to retain, after
whichnewer WALs will be removed and the primary server saved. Pretty much like : --archive-push-queue-max argument of
pgbackrest.
>>
>
>
> --
> Achilleas Mantzios
> IT DEV Lead
> IT DEPT
> Dynacom Tankers Mgmt
>
>