On 07/02/17 16:26, Petr Jelinek wrote:
> On 07/02/17 13:10, Masahiko Sawada wrote:
>> I think the logical replication should not stop and the corresponding
>> replication slot and replication origin should not be removed until
>> the transaction commits.
>> The solution for this I came up with is that the launcher process
>> stops the apply worker after DROP SUBSCRIPTION is committed rather
>> than DropSubscription does. And the apply worker drops replication
>> slot and replication origin before exits. Attached draft patch fixes
>> this issue.
> I don't think we can allow the slot drop to be postponed. There is too
> many failure scenarios where we would leave the remote slot in the
> database and that's not acceptable IMHO.
> For example what happens if apply crashes during the DROP
> SUBSCRIPTION/COMMIT and is not started because the delete from catalog
> is now visible so the subscription is no longer there?

Not to mention that slot creation/drop is not transactional by itself so
even if there was some way to tie remote transaction to local
transaction (like say 2pc), it would still not work with ROLLBACK.

  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services

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