Charmed PostgreSQL VM Tutorial > 5. Integrate with other applications
Integrate with other applications
Integrations, known as “relations” in Juju 2.9, are the easiest way to create a user for PostgreSQL in Charmed PostgreSQL VM.
Integrations automatically create a username, password, and database for the desired user/application. As mentioned earlier in 2. Deploy PostgreSQL , it is a better practice to connect to PostgreSQL via a specific user rather than the admin user.
In this section, you will integrate your Charmed PostgreSQL to another charmed application.
Summary
Deploy data-integrator
Before relating to a charmed application, we must first deploy our charmed application. In this tutorial, we will relate to the Data Integrator charm. This is a bare-bones charm that allows for central management of database users, providing support for different kinds of data platforms (e.g. PostgreSQL, MySQL, MongoDB, Kafka, etc) with a consistent, opinionated and robust user experience.
To deploy data-integrator, run
juju deploy data-integrator --config database-name=test-database
The expected output:
Located charm "data-integrator" in charm-hub, revision 11
Deploying "data-integrator" from charm-hub charm "data-integrator", revision 11 in channel stable on jammy
Checking the deployment progress using juju status will show a blocked state for the newly deployed charm:
Model Controller Cloud/Region Version SLA Timestamp
tutorial overlord localhost/localhost 3.1.7 unsupported 10:22:13+01:00
App Version Status Scale Charm Channel Rev Exposed Message
data-integrator blocked 1 data-integrator stable 11 no Please relate the data-integrator with the desired product
postgresql active 2 postgresql 14/stable 281 no
Unit Workload Agent Machine Public address Ports Message
data-integrator/0* blocked idle 3 10.89.49.179 Please relate the data-integrator with the desired product
postgresql/0* active idle 0 10.89.49.129
postgresql/1 active idle 1 10.89.49.197
Machine State Address Inst id Series AZ Message
0 started 10.89.49.129 juju-a8a31d-0 jammy Running
1 started 10.89.49.197 juju-a8a31d-1 jammy Running
3 started 10.89.49.179 juju-a8a31d-3 jammy Running
The blocked state is expected due to not-yet established relation (integration) between applications.
Integrate with PostgreSQL
Now that the data-integrator charm has been set up, we can relate it to PostgreSQL. This will automatically create a username, password, and database for data-integrator.
Relate the two applications with:
juju integrate data-integrator postgresql
Wait for juju status --watch 1s to show all applications/units as active:
Model Controller Cloud/Region Version SLA Timestamp
tutorial overlord localhost/localhost 3.1.7 unsupported 10:22:31+01:00
App Version Status Scale Charm Channel Rev Exposed Message
data-integrator active 1 data-integrator stable 11 no
postgresql active 2 postgresql 14/stable 281 no
Unit Workload Agent Machine Public address Ports Message
data-integrator/0* active idle 3 10.89.49.179
postgresql/0* active idle 0 10.89.49.129 Primary
postgresql/1 active idle 1 10.89.49.197
Machine State Address Inst id Series AZ Message
0 started 10.89.49.129 juju-a8a31d-0 jammy Running
1 started 10.89.49.197 juju-a8a31d-1 jammy Running
3 started 10.89.49.179 juju-a8a31d-3 jammy Running
To retrieve information such as the username, password, and database, run the command
juju run data-integrator/leader get-credentials
This should output something like:
unit-data-integrator-0:
UnitId: data-integrator/0
id: "20"
results:
ok: "True"
postgresql:
database: test-database
endpoints: 10.89.49.129:5432
password: 136bvw0s7FjJ6mxZ
read-only-endpoints: 10.89.49.197:5432
username: relation-3
version: "14.7"
status: completed
timing:
completed: 2023-03-20 09:22:50 +0000 UTC
enqueued: 2023-03-20 09:22:46 +0000 UTC
started: 2023-03-20 09:22:50 +0000 UTC
Note that your hostnames, usernames, and passwords will likely be different.
Access the related database
Use endpoints, username, password from above to connect newly created database test-database on the PostgreSQL server:
> psql --host=10.89.49.129 --username=relation-3 --password test-database
...
test-database=> \l
...
test-database | operator | UTF8 | C.UTF-8 | C.UTF-8 | =Tc/operator +
| | | | | operator=CTc/operator +
| | | | | "relation-3"=CTc/operator
...
The newly created database test-database is also available on all other PostgreSQL cluster members:
> psql --host=10.89.49.197 --username=relation-3 --password --list
...
test-database | operator | UTF8 | C.UTF-8 | C.UTF-8 | =Tc/operator +
| | | | | operator=CTc/operator +
| | | | | "relation-3"=CTc/operator
...
When you relate two applications, Charmed PostgreSQL automatically sets up a new user and database for you.
Note the database name we specified when we first deployed the data-integrator charm: --config database-name=test-database.
Remove the user
Removing the integration automatically removes the user that was created when the integration was created. Enter the following to remove the integration:
juju remove-relation postgresql data-integrator
Now try again to connect to the same PostgreSQL you just used in the previous section:
> psql --host=10.89.49.129 --username=relation-3 --password --list
This will output an error message like the one shown below:
psql: error: connection to server at "10.89.49.129", port 5432 failed: FATAL: password authentication failed for user "relation-3"
This is expected, since this user no longer exists after removing the integration.
Data remains on the server at this stage.
To create a user again, integrate the applications again:
juju integrate data-integrator postgresql
Re-integrating generates a new user and password:
juju run data-integrator/leader get-credentials
You can then connect to the database with these new credentials. From here you will see all of your data is still present in the database.
Next step: 6. Enable TLS