Re: Replication slots and footguns

On Thu, Mar 13, 2014 at 5:45 AM, Thom Brown <thom@linux.com> wrote:
> On 12 March 2014 19:00, Josh Berkus <josh@agliodbs.com> wrote:
>> All:
>>
>> I was just reading Michael's explanation of replication slots
>> (http://michael.otacoo.com/postgresql-2/postgres-9-4-feature-highlight-replication-slots/)
>> and realized there was something which had completely escaped me in the
>> pre-commit discussion:
>>
>> select pg_drop_replication_slot('slot_1');
>> ERROR:  55006: replication slot "slot_1" is already active
>> LOCATION:  ReplicationSlotAcquire, slot.c:339
>>
>> What defines an "active" slot?
>>
>> It seems like there's no way for a DBA to drop slots from the master if
>> it's rapidly running out of disk WAL space without doing a restart, and
>> there's no way to drop the slot for a replica which the DBA knows is
>> permanently offline but was connected earlier.  Am I missing something?
>
> I'm not clear on why would dropping an active replication slot would
> solve disk space problems related to WAL.  I thought it was inactive
> slots that were the problem in this regard?
You could still have an active slot with a standby that is not able to
catch up AFAIK.
--
Michael