Logical replication DNS cache

Started by Mike Lissnerover 6 years ago2 messagesgeneral
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#1Mike Lissner
mlissner@michaeljaylissner.com

I've got a server at example.com that currently publishes logical
replication to a server in AWS RDS. I plan to move the server at example.com
so that it has a new IP address (but same domain name).

I'm curious if anybody knows how the logical replication subscriber in AWS
would handle that.

There's at least three layers where the DNS might be cached, creating
breakage once the move is complete:

- Postgres itself

- AWS's postgresql fork in RDS might have something

- The OS underlying amazon's RDS service

I expect this is a tough question unless somebody has done this before, but
any ideas on how postgresql would handle this kind of thing? Or is there a
way to flush the DNS cache that postgresql (or RDS or the OS) has?

I'm just beginning to explore this, but if anybody has experience, I'd love
to hear it.

Thanks,

Mike

#2Peter Eisentraut
peter_e@gmx.net
In reply to: Mike Lissner (#1)
Re: Logical replication DNS cache

On 2019-12-12 01:37, Mike Lissner wrote:

I've got a server at example.com <http://example.com&gt; that currently
publishes logical replication to a server in AWS RDS. I plan to move the
server at example.com <http://example.com&gt; so that it has a new IP
address (but same domain name).

I'm curious if anybody knows how the logical replication subscriber in
AWS would handle that.

There's at least three layers where the DNS might be cached, creating
breakage once the move is complete:

 - Postgres itself

 - AWS's postgresql fork in RDS might have something

 - The OS underlying amazon's RDS service

Postgres itself doesn't cache any host name resolution results. I don't
know about the other two pieces.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services