Relate your MongoDB deployment

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

Relations

Relations, or what Juju documentation describes as Integration, are the easiest way to create a user for MongoDB in Charmed MongoDB. Relations automatically create a username, password, and database for the desired user/application. As mentioned earlier in the Access MongoDB section it is a better practice to connect to MongoDB via a specific user rather than the admin user.

Data Integrator Charm

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. MongoDB, MySQL, PostgreSQL, Kafka, etc) with a consistent, opinionated and robust user experience. In order to deploy the Data Integrator Charm we can use the command juju deploy we have learned above:

juju deploy data-integrator --channel edge --config database-name=test-database

The expected output:

Located charm "data-integrator" in charm-hub...
Deploying "data-integrator" from charm-hub charm "data-integrator"...

Relate to MongoDB

Now that the Database Integrator Charm has been set up, we can relate it to MongoDB. This will automatically create a username, password, and database for the Database Integrator Charm. Relate the two applications with:

juju relate data-integrator mongodb

Wait for juju status --watch 1s to show:

ubuntu@ip-172-31-11-104:~/data-integrator$ juju status
Model     Controller  Cloud/Region         Version  SLA          Timestamp
tutorial  overlord    localhost/localhost  2.9.37   unsupported  10:32:09Z

App                  Version  Status  Scale  Charm                Channel   Rev  Exposed  Message
data-integrator               active      1  data-integrator      edge       3   no
mongodb                       active      2  mongodb              5/edge   96  no

Unit                    Workload  Agent  Machine  Public address  Ports      Message
data-integrator/0*  active    idle   5        10.23.62.216               received mongodb credentials
mongodb/0*              active    idle   0        10.23.62.156    27017/tcp
mongodb/1               active    idle   1        10.23.62.55     27017/tcp  Replica set primary

Machine  State    Address       Inst id        Series  AZ  Message
0        started  10.23.62.156  juju-d35d30-0  jammy       Running
1        started  10.23.62.55   juju-d35d30-1  jammy       Running
5        started  10.23.62.216  juju-d35d30-5  jammy       Running

To retrieve information such as the username, password, and database. Enter:

juju run-action data-integrator/leader get-credentials --wait

This should output something like:

​​unit-data-integrator-0:
  UnitId: data-integrator/0
  id: "24"
  results:
    mongodb:
      database: test-database
      endpoints: 10.23.62.55,10.23.62.156
      password: VMnRws6BlojzDi5e1m2GVWOgJaoSs44d
      replset: mongodb
      uris: mongodb://relation-4:VMnRws6BlojzDi5e1m2GVWOgJaoSs44d@10.23.62.55,10.23.62.156/test-database?replicaSet=mongodb&authSource=admin
      username: relation-4
    ok: "True"
  status: completed
  timing:
    completed: 2022-12-06 10:33:24 +0000 UTC
    enqueued: 2022-12-06 10:33:20 +0000 UTC
    started: 2022-12-06 10:33:24 +0000 UTC

Save the value listed under uris: (Note: your hostnames, usernames, and passwords will likely be different.)

Access the related database

Notice that in the previous step when you typed juju run-action data-integrator/leader get-credentials --wait the command not only outputted the username, password, and database, but also outputted the URI. This means you do not have to generate the URI yourself. To connect to this URI first ssh into mongodb/0:

juju ssh mongodb/0

Then access mongo with the URI that you copied above:

charmed-mongodb.mongo "<uri copied from juju run-action data-integrator/leader get-credentials --wait>"

Note: be sure you wrap the URI in " with no trailing whitespace.

You will now be in the mongo shell as the user created for this relation. When you relate two applications Charmed MongoDB automatically sets up a user and database for you. Enter db.getName() into the MongoDB shell, this will output:

test-database

This is the name of the database we specified when we first deployed the data-integrator charm. To create a collection in the “test-database” and then show the collection enter:

db.createCollection("test-collection")
show collections

Now insert a document into this database:

db.test_collection.insertOne(
  {
    First_Name: "Jammy",
    Last_Name: "Jellyfish",
  })

You can verify this document was inserted by running:

db.test_collection.find()

Now exit the MongoDB shell by typing:

exit

Now you should be back in the host of Charmed MongoDB (mongodb/0). To exit this host type:

exit

You should now be shell you started in where you can interact with Juju and LXD.

Remove the user

To remove the user, remove the relation. Removing the relation automatically removes the user that was created when the relation was created. Enter the following to remove the relation:

juju remove-relation mongodb data-integrator

Now try again to connect to the same URI you just used in Access the related database:

juju ssh mongodb/0
charmed-mongodb.mongo "<uri copied from juju run-action data-integrator/leader get-credentials --wait>"

Note: be sure you wrap the URI in " with no trailing whitespace.

This will output an error message:

Current Mongosh Log ID: 638f5ffbdbd9ec94c2e58456
Connecting to:    mongodb://<credentials>@10.23.62.38,10.23.62.219/mongodb?replicaSet=mongodb&authSource=admin&appName=mongosh+1.6.1
MongoServerError: Authentication failed.

As this user no longer exists. This is expected as juju remove-relation mongodb data-integrator also removes the user.

Now exit the juju:

exit

You should now be shell you started in where you can interact with Juju and LXD.

If you wanted to recreate this user all you would need to do is relate the the two applications again:

juju relate data-integrator mongodb

Re-relating generates a new password for this user, and therefore a new URI you can see the new URI with:

juju run-action data-integrator/leader get-credentials --wait

Save the result listed with uris:.

You can connect to the database with this new URI:

juju ssh mongodb/0
charmed-mongodb.mongo "<uri copied from juju run-action data-integrator/leader get-credentials --wait>"

Note: be sure you wrap the URI in " with no trailing whitespace.

From there if you enter db.test_collection.find() you will see all of your original documents are still present in the database.

Now exit the MongoDB shell by typing:

exit

Now you should be back in the host of Charmed MongoDB (mongodb/0). To exit this host type:

exit

You should now be shell you started in where you can interact with Juju and LXD.