Re: PostgreSQL logical replication depends on WAL segments?

On 22/1/19 6:01 μ.μ., Josef Machytka wrote:
>
> https://www.postgresql.org/docs/11/logical-replication-architecture.html
>
>
> Thanks, I see... So if I understand it correctly - since I have quite big partitions like ~30 GB each in one parent table and from ~1GB to ~5 GB in several others I presume I had to set
> wal_keep_segments to some really high number and stop our security cronjob cleaning old WAL segments (because we already had some problems with almost full disk due to old WAL segments)

I asked you if you had any cron jobs messing around with your WALs. The WALs in pg_wal dir is PostgreSQL's business to manage, not your scripts. Dont do that. Defining wal_keep_segments to a very
large value or using replication slots (as with logical repl) won't help if your crons are deleting the WALs.
Now what you have to do :
- read up about the basic concepts of pgsql administration : https://www.postgresql.org/docs/11/admin.html
- understand how postgresql replication slots work (logical repl is based on those)
- understand how WAL archiving works
- understand how streaming replication works
- understand how logical replication works
- understand how the various runtime configuration params act on the number of WALs kept

> until the whole transfer of snapshot is done. Because only after the whole snapshot is transferred logical replication workers start to transfer WAL logs reflecting changes done from the moment
> snapshot was taken...
>
> jm

--
Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt