Scale your MySQL Router K8s

This is part of the Charmed MySQL 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 MySQL K8s operator here.

Add more mysql-router instances

You can add two more units to your deployed MySQL Router application by scaling it to three units using:

juju scale-application mysql-router-k8s 3

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  overlord    microk8s/localhost  2.9.46   unsupported  22:48:57+01:00

App               Version                  Status  Scale  Charm             Channel   Rev  Address         Exposed  Message
data-integrator                            active      1  data-integrator   stable     13  10.152.183.142  no       
mysql-k8s         8.0.34-0ubuntu0.22.04.1  active      1  mysql-k8s         8.0/edge  109  10.152.183.68   no       
mysql-router-k8s  8.0.34-0ubuntu0.22.04.1  active      3  mysql-router-k8s  8.0/edge   68  10.152.183.52   no       

Unit                 Workload  Agent  Address     Ports  Message
data-integrator/0*   active    idle   10.1.12.3          
mysql-k8s/0*         active    idle   10.1.12.36         Primary
mysql-router-k8s/0*  active    idle   10.1.12.14         
mysql-router-k8s/1   active    idle   10.1.12.32         
mysql-router-k8s/2   active    idle   10.1.12.31  

The same way you can scale Charmed MySQL:

juju scale-application mysql-k8s 3

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

App               Version                  Status  Scale  Charm             Channel   Rev  Address         Exposed  Message
data-integrator                            active      1  data-integrator   stable     13  10.152.183.142  no       
mysql-k8s         8.0.34-0ubuntu0.22.04.1  active      3  mysql-k8s         8.0/edge  109  10.152.183.68   no       
mysql-router-k8s  8.0.34-0ubuntu0.22.04.1  active      3  mysql-router-k8s  8.0/edge   68  10.152.183.52   no       

Unit                 Workload  Agent  Address     Ports  Message
data-integrator/0*   active    idle   10.1.12.3          
mysql-k8s/0*         active    idle   10.1.12.36         Primary
mysql-k8s/1          active    idle   10.1.12.34         
mysql-k8s/2          active    idle   10.1.12.43         
mysql-router-k8s/0*  active    idle   10.1.12.14         
mysql-router-k8s/1   active    idle   10.1.12.32         
mysql-router-k8s/2   active    idle   10.1.12.31  

Remove extra members

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

juju scale-application mysql-router-k8s 2
juju scale-application mysql-k8s 2

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

Model     Controller  Cloud/Region        Version  SLA          Timestamp
tutorial  overlord    microk8s/localhost  2.9.46   unsupported  22:48:57+01:00

App               Version                  Status  Scale  Charm             Channel   Rev  Address         Exposed  Message
data-integrator                            active      1  data-integrator   stable     13  10.152.183.142  no       
mysql-k8s         8.0.34-0ubuntu0.22.04.1  active      2  mysql-k8s         8.0/edge  109  10.152.183.68   no       
mysql-router-k8s  8.0.34-0ubuntu0.22.04.1  active      2  mysql-router-k8s  8.0/edge   68  10.152.183.52   no       

Unit                 Workload  Agent  Address     Ports  Message
data-integrator/0*   active    idle   10.1.12.3          
mysql-k8s/0*         active    idle   10.1.12.36         Primary
mysql-k8s/1          active    idle   10.1.12.34         
mysql-router-k8s/0*  active    idle   10.1.12.14         
mysql-router-k8s/1   active    idle   10.1.12.32