Scale your PgBouncer

This is part of the PgBouncer Tutorial. Please refer to this page for more information and the overview of the content.

Adding and Removing units

Please check the explanation of scaling Charmed PostgreSQL operator here.

Add more pgbouncer instances

PgBouncer is a subordinated charm, it is enough to keep it as a single instance for each principal charm. To scale the principal charm use juju add-unit command (for a tutorial purpose let’s scale data-integrator):

juju add-unit data-integrator -n 2

You can now watch the scaling process in live using: juju status --watch 1s. It usually takes several minutes for new cluster members to be added. You’ll know that all three nodes are in sync when juju status reports Workload=active and Agent=idle:

Model     Controller  Cloud/Region         Version  SLA          Timestamp
tutorial  lxd         localhost/localhost  3.1.6    unsupported  22:26:56+02:00

App              Version  Status  Scale  Charm            Channel    Rev  Exposed  Message
data-integrator           active      3  data-integrator  stable      13  no       
pgbouncer        1.18.0   active      3  pgbouncer        1/stable    76  no       
postgresql       14.9     active      1  postgresql       14/stable  336  no       Primary

Unit                Workload  Agent  Machine  Public address  Ports     Message
data-integrator/1*  active    idle   2        10.3.217.158              
  pgbouncer/1*      active    idle            10.3.217.158              
data-integrator/2   active    idle   3        10.3.217.83               
  pgbouncer/3       active    idle            10.3.217.83               
data-integrator/3   active    idle   4        10.3.217.35               
  pgbouncer/2       active    idle            10.3.217.35               
postgresql/0*       active    idle   0        10.3.217.79     5432/tcp  Primary

Machine  State    Address       Inst id        Base          AZ  Message
0        started  10.3.217.79   juju-ca0eed-0  ubuntu@22.04      Running
2        started  10.3.217.158  juju-ca0eed-2  ubuntu@22.04      Running
3        started  10.3.217.83   juju-ca0eed-3  ubuntu@22.04      Running
4        started  10.3.217.35   juju-ca0eed-4  ubuntu@22.04      Running

The same way you can scale Charmed PostgreSQL:

juju add-unit postgresql -n 2

Make sure all units are active (using juju status):

Model     Controller  Cloud/Region         Version  SLA          Timestamp
tutorial  lxd         localhost/localhost  3.1.6    unsupported  22:55:52+02:00

App              Version  Status  Scale  Charm            Channel    Rev  Exposed  Message
data-integrator           active      3  data-integrator  stable      13  no       
pgbouncer        1.18.0   active      3  pgbouncer        1/stable    76  no       
postgresql       14.9     active      3  postgresql       14/stable  336  no       

Unit                Workload  Agent  Machine  Public address  Ports     Message
data-integrator/1*  active    idle   2        10.3.217.158              
  pgbouncer/1*      active    idle            10.3.217.158              
data-integrator/2   active    idle   3        10.3.217.83               
  pgbouncer/3       active    idle            10.3.217.83               
data-integrator/3   active    idle   4        10.3.217.35               
  pgbouncer/2       active    idle            10.3.217.35               
postgresql/0*       active    idle   0        10.3.217.79     5432/tcp  Primary
postgresql/1        active    idle   5        10.3.217.147    5432/tcp  
postgresql/2        active    idle   6        10.3.217.114    5432/tcp  

Machine  State    Address       Inst id        Base          AZ  Message
0        started  10.3.217.79   juju-ca0eed-0  ubuntu@22.04      Running
2        started  10.3.217.158  juju-ca0eed-2  ubuntu@22.04      Running
3        started  10.3.217.83   juju-ca0eed-3  ubuntu@22.04      Running
4        started  10.3.217.35   juju-ca0eed-4  ubuntu@22.04      Running
5        started  10.3.217.147  juju-ca0eed-5  ubuntu@22.04      Running
6        started  10.3.217.114  juju-ca0eed-6  ubuntu@22.04      Running

Remove extra members

Removing a unit from the application, scales the replicas down.

juju remove-unit data-integrator/2
juju remove-unit data-integrator/1
juju remove-unit postgresql/1
juju remove-unit postgresql/2

You’ll know that the replica was successfully removed when juju status --watch 1s reports:

Model     Controller  Cloud/Region         Version  SLA          Timestamp
tutorial  lxd         localhost/localhost  3.1.6    unsupported  22:56:23+02:00

App              Version  Status  Scale  Charm            Channel    Rev  Exposed  Message
data-integrator           active      1  data-integrator  stable      13  no       
pgbouncer        1.18.0   active      1  pgbouncer        1/stable    76  no       
postgresql       14.9     active      1  postgresql       14/stable  336  no       

Unit                Workload  Agent  Machine  Public address  Ports     Message
data-integrator/3*  active    idle   4        10.3.217.35               
  pgbouncer/2*      active    idle            10.3.217.35               
postgresql/0*       active    idle   0        10.3.217.79     5432/tcp  

Machine  State    Address      Inst id        Base          AZ  Message
0        started  10.3.217.79  juju-ca0eed-0  ubuntu@22.04      Running
4        started  10.3.217.35  juju-ca0eed-4  ubuntu@22.04      Running