Subject: Re: replication_slots usability issue
To: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org,
 pgsql-hackers <pgsql-hackers@postgresql.org>
References: <56672097-711c-126a-a63e-04e7940110ad@commandprompt.com>
 <835C001D-7F0B-4C90-BFB3-5D6EE5E71A21@anarazel.de>
From: "Joshua D. Drake" <jd@commandprompt.com>
Organization: Command Prompt, Inc.
Message-ID: <cc681364-c4e3-c288-fd6f-b7a8b52c3fa4@commandprompt.com>
Date: Mon, 29 Oct 2018 15:13:07 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <835C001D-7F0B-4C90-BFB3-5D6EE5E71A21@anarazel.de>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Precedence: bulk

On 10/29/18 11:26 AM, Andres Freund wrote:
>
> On October 29, 2018 1:31:56 PM EDT, "Joshua D. Drake" <jd@commandprompt.com> wrote:
>> -Hackers,
>>
>>
>> Working on 9.6 today (unsure if fixed in newer versions). Had an issue
>> where the wal was 280G despite max_wal_size being 8G. Found out there
>> were stale replication slots from a recent base backup. I went to drop
>> the replication slots and found that since the wal_level was set to
>> minimal vs replica or higher, I couldn't drop the replication slot.
>> Clearly that makes sense for creating a replication slot but it seems
>> like an artificial limitation for dropping them.
> Uh, huh? How did you manage to start a server with existing slots with that configuration? It should have errored out at start...

Well, this is the recovery.conf:

standby_mode = 'on'
recovery_target = 'immediate'
primary_slot_name = 'testing_db01'
primary_conninfo = 'user=replication 
passfile=/var/lib/postgresql/.pgpass host=db01 port=5432 sslmode=prefer 
sslcompression=1 krbsrvname=postgres target_session_attrs=any'

recovery_target_action = 'promote'

The machine came up clean and the only reason I noticed the problem is 
that it ran out of disk space. I cleared enough disk space to get it to 
come up again and noticed that there were replication slots that were 
identical to the primary.


JD


-- 
Command Prompt, Inc. || http://the.postgres.company/ || @cmdpromptinc
***  A fault and talent of mine is to tell it exactly how it is.  ***
PostgreSQL centered full stack support, consulting and development.
Advocate: @amplifypostgres || Learn: https://postgresconf.org
*****     Unless otherwise stated, opinions are my own.   *****