Re: Highly academic: local etcd & Patroni Cluster for testing on asingle host

On 2020/02/26 0:41, Paul Förster wrote:
> Hi,
> 
> I have set up an etcd & Patroni cluster on a single machine for testing purposes as follows:
> 
> /data/pg01a/db as data directory for the first "node"
> /data/pg01b/db as data directory for the second "node"
> 
> I have set up Patroni to make each PostgreSQL database cluster archive to its own destination, so they won't
interferewith each other. All is well and working fine so far. Failover/Switchover works, they are syncing properly,
etc.
> 
> Now:
> 
> Inside /data/pg01a and /data/pg01b I also have a directory ts, i.e. /data/pg01a/ts and /data/pg01b/ts to simulate
differentfilesystems.
 
> 
> If I do a 'create tablespace' and specify its location, I must of course specify either /data/pg01a/ts or
/data/pg01b/ts.
> 
> Files with Tables get created as usual, but since it's a replication (sync, by the way), the other tablespace
directorywill not hold any files, but instead, the replica uses the same files as does the master.
 
> 
> Is there any way around that, i.e. make the replica use its own files? I found a way to make each archive destination
individualdespite Patroni, but I can't seem to find a way to do something similar to the tablespaces. Even correcting
thesymlinks in ${PGDATA}/pg_tblspc manually (and then restart) does not work.
 
> 
> The explanation is simple: the location is stored inside the database cluster information and is per definition the
sameacross all nodes. So, if 'a' is master and I do "create tablespace test location '/data/pg01a/ts'" it creates files
therewith the replica 'b' using the *same* destination.
 
> 
> Still, is there a way to make each node store that information individually? I know, this is highly academic but I
onlyhave a single host to do etcd & Patroni cluster experiments on.
 

Assuming the standby/replica is created using pg_basebackup, you can use the
-T/--tablespace-mapping option to remap the tablespace directories.


Regards

Ian Barwick

-- 
Ian Barwick                   https://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services