Hi,
> Can you share an example as to what you mean by folder keeps
> increasing? Is the slot size on disk is increasing?
The size on the disk keeps increasing. Last week, it went upto 35 GB per slot, then I had to put a 20GB limit on max_slot_wal_keep_size. After reaching the size limit, the subscriptions went inactive. Then I dropped the subscriptions and freed up the replication slots.
> To understand the problem you are facing, we need to see some real
> data on the size. Can you share the output of pg_replication_slots
> both before and after the folder's size increase?
I cannot share the real data right now because I have dropped the subscriptions and publications altogether. I can create them again tonight (I am in India) and share the details tomorrow.
> Is it possible to share a reproducer or some steps to reproduce the problem?
What I had was a straightforward logical replication setup. We had two publications and six subscribing servers. Please also note that this setup was working fine with PostgreSQL 15. During May we upgraded to 17.5, and ran into a bug which is described in the following release notes section of 17.6
Avoid re-distributing cache invalidation messages from other transactions during logical replication (vignesh C) §
Our previous round of minor releases included a bug fix to ensure that replication receiver processes would respond to cross-process cache invalidation messages, preventing them from using stale catalog data while performing replication updates. However, the fix unintentionally made them also redistribute those messages again, leading to an exponential increase in the number of invalidation messages, which would often end in a memory allocation failure. Fix by not redistributing received messages.
Due to the bug, we stopped using logical replication and started it again after updating to 17.6. Now we are having this issue.
Thadeus Anand.
On Mon, Aug 25, 2025 at 10:39 AM Thadeus Anand <thadeus@rmkv.com> wrote:
>
> Hi,
>
> The number of replication slots does not increase at all. But the size of each folder keeps increasing simultaneously.
>
Can you share an example as to what you mean by folder keeps
increasing? Is the slot size on disk is increasing?
> When I restart a subscriber, the size of the respective slot resets, then immediately grows up to the size of the slots of other subscribers.
>
To understand the problem you are facing, we need to see some real
data on the size. Can you share the output of pg_replication_slots
both before and after the folder's size increase?
> The table data is properly synchronized across the locations, and the status of the replication remains as 'streaming'. So, effectively, the logical replication works (which it wasn't in version 17.5), but the replication slot isn't resetting.
>
Is it possible to share a reproducer or some steps to reproduce the problem?
--
With Regards,
Amit Kapila.
