On Wed, Mar 10, 2021 at 3:56 AM Martín Fernández <fmarti...@gmail.com> wrote:
> Hello, > > I’m troubleshooting a problem at my company with a pg 12 cluster that we > run. > > We are using Amazon DMS to replicate data from our database into S3 > buckets. DMS replicates data by using logical replication slots. > > After introducing DMS in our environment, we have seen an increase in CPU > load of 20 points at business hours (from ~60% to ~80%). > > The other thing that we have identified is that AccessShareLocks increase > considerably when DMS running. > > Based on this information, I’m trying to understand if this is something > expected when running logical replication or not. We’ve been running > physical replication for several years and we haven’t seen nothing like > this. It could be the case that the issue is not related at all with > logical replication and is purely a DMS artifact. > > Thanks before hand! > > Best, > Martín > > Hi, I would check in pg_stat_activity what those logical replication slots do. I guess COPY. Are you doing one shot copy ? every day ? Then copying all the tables will lead to load increase. How many tables at a time DMS copies? It should be configurable. AccessShareLock is absolutely normal. You have a transaction doing SELECT (COPY) over a table. Physical replication is a different thing. It happens at another level. Regards Rado
