Charmed PostgreSQL K8s Tutorial - Deploy Charmed PostgreSQL K8s

Charmed PostgreSQL K8s Tutorial > 2. Deploy PostgreSQL

Deploy Charmed PostgreSQL K8s

In this section, you will deploy Charmed PostgreSQL K8s, access the units hosting this charm, and interact with the PostgreSQL databases that exist inside the application.

Note: All commands are written for juju >= v.3.0

If you are using an earlier version, be aware that:

  • juju run replaces juju run-action --wait in juju v.2.9
  • juju integrate replaces juju relate and juju add-relation in juju v.2.9

For more information, check the Juju 3.0 Release Notes.

Deploy

To deploy Charmed PostgreSQL, all you need to do is run

juju deploy postgresql-k8s --channel 14/stable --trust

--trust is required because the charm and Patroni need to create some K8s resources.

Juju will now fetch Charmed PostgreSQL K8s from Charmhub and deploy it to the local MicroK8s. This process can take several minutes depending on how provisioned (RAM, CPU, etc) your machine is.

You can track the progress by running:

juju status --watch 1s

This command is useful for checking the real-time information about the state of a charm and the machines hosting it. Check the juju status documentation for more information about its usage.

When the application is ready, juju status will show something similar to the sample output below:

Model     Controller  Cloud/Region        Version  SLA          Timestamp
tutorial  charm-dev   microk8s/localhost  2.9.42   unsupported  12:00:43+01:00

App             Version  Status  Scale  Charm           Channel    Rev  Address         Exposed  Message
postgresql-k8s           active      1  postgresql-k8s  14/stable  56   10.152.183.167  no

Unit               Workload  Agent  Address       Ports  Message
postgresql-k8s/0*  active    idle   10.1.188.206

You can also watch juju logs with the juju debug-log command. More info on logging in the juju logs documentation.

Access PostgreSQL

Warning: This part of the tutorial accesses PostgreSQL via the operator user.

Do not directly interface with the operator user in a production environment.

In a later section about Integrations, we will cover how to safely access PostgreSQL by creating a separate user via the Data Integrator charm

Connecting to the database requires that you know the values for host, username and password.

To retrieve these values, run the Charmed PostgreSQL K8s action get-password:

juju run postgresql-k8s/leader get-password

Running the command above should output:

unit-postgresql-k8s-0:
  UnitId: postgresql-k8s/0
  id: "2"
  results:
    password: SYhCduijXTAfg9mU
  status: completed
  timing:
    completed: 2023-03-20 11:01:26 +0000 UTC
    enqueued: 2023-03-20 11:01:24 +0000 UTC
    started: 2023-03-20 11:01:25 +0000 UTC

To request a password for a different user, use the option username:

juju run postgresql-k8s/leader get-password username=replication

The IP address of the unit hosting the PostgreSQL application, also referred to as the “host”, can be found with juju status:

...
Unit               Workload  Agent  Address       Ports  Message
postgresql-k8s/0*  active    idle   10.1.188.206
...

To access the units hosting Charmed PostgreSQL K8s run

juju ssh --container postgresql postgresql-k8s/leader bash

If at any point you’d like to leave the unit hosting Charmed PostgreSQL K8s, enter Ctrl+D or type exit.

The easiest way to access PostgreSQL is via the PostgreSQL interactive terminal psql, which is already installed here.

To list all available databases, run:

psql --host=10.1.188.206 --username=operator --password --list

When requested, enter the <password> for charm user operator that you obtained earlier.

Example output:

                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | operator | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | operator | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/operator          +
           |          |          |             |             | operator=CTc/operator
 template1 | operator | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/operator          +
           |          |          |             |             | operator=CTc/operator
(3 rows)

You can now interact with PostgreSQL directly using PostgreSQL SQL Queries. For example, entering SELECT version(); should output something like:

> root@postgresql-k8s-0:/# psql --host=10.1.188.206 --username=operator --password postgres
Password:
psql (14.5 (Ubuntu 14.5-0ubuntu0.22.04.1))
Type "help" for help.

postgres=# SELECT version();
                                                             version
---------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 14.5 (Ubuntu 14.5-0ubuntu0.22.04.1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 11.2.0-19ubuntu1) 11.2.0, 64-bit
(1 row)

Feel free to test out any other PostgreSQL queries.

When you’re ready to leave the PostgreSQL shell, you can just type exit. This will take you back to the host of Charmed PostgreSQL K8s (postgresql-k8s/0). Exit this host by once again typing exit. Now you will be in your original shell where you first started the tutorial. Here you can interact with Juju and MicroK8s.