Relate your MongoDB deployment

This is part of the Charmed MongoDB K8s 5 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 K8s. 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 products (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 previously:

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-k8s

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

Model     Controller  Cloud/Region        Version  SLA          Timestamp
tutorial  overlord    microk8s/localhost  3.1.6   unsupported  17:24:23Z

App              Version  Status  Scale  Charm            Channel  Rev  Address         Exposed  Message
data-integrator           active      1  data-integrator  edge      11  10.152.183.190  no
mongodb-k8s               active      2  mongodb-k8s      5/edge    27  10.152.183.20   no

Unit                Workload    Agent  Address      Ports  Message
data-integrator/0*  active      idle   10.1.42.142
mongodb-k8s/0*      active      idle   10.1.42.137
mongodb-k8s/1       active      idle   10.1.42.140

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

juju run data-integrator/leader get-credentials

This should output something like:

Running operation 19 with 1 task
  - task 20 on unit-data-integrator-0

Waiting for task 20...
mongodb:
  database: test-database
  endpoints: mongodb-k8s-0.mongodb-k8s-endpoints,mongodb-k8s-1.mongodb-k8s-endpoints
  password: iW19U0ClFbSDurxMju98Zsgy4BovY4uf
  replset: mongodb-k8s
  uris: mongodb://relation-2:iW19U0ClFbSDurxMju98Zsgy4BovY4uf@mongodb-k8s-0.mongodb-k8s-endpoints,mongodb-k8s-1.mongodb-k8s-endpoints/test-database?replicaSet=mongodb-k8s&authSource=admin
  username: relation-2
ok: "True"

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-k8s/0:

juju ssh --container=mongod mongodb-k8s/0

Then access mongo with the URI that you copied above:

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 K8s 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 the Charmed MongoDB K8s’s unit: mongodb-k8s/0. To exit this host type:

exit

You should now be in the shell you started where you can interact with Juju and Kubernetes (Microk8s).

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-k8s data-integrator

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

juju ssh --container=mongod mongodb-k8s/0
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:

Percona Server for MongoDB shell version v5.0.15-13
connecting to: mongodb://mongodb-k8s-2.mongodb-k8s-endpoints:27017,mongodb-k8s-1.mongodb-k8s-endpoints:27017,mongodb-k8s-0.mongodb-k8s-endpoints:27017/test-database?authSource=admin&compressors=disabled&gssapiServiceName=mongodb&replicaSet=mongodb-k8s
Error: can't connect to new replica set primary [mongodb-k8s-0.mongodb-k8s-endpoints:27017], err: AuthenticationFailed: Authentication failed. :
connect@src/mongo/shell/mongo.js:372:17
@(connect):2:6
exception: connect failed
exiting with code 1
# 

As this user no longer exists. This is expected as juju remove-relation mongodb-k8s data-integrator also removes the user.

Now exit the juju:

exit

You should now be in the shell you started where you can interact with Juju and Kubernetes (Microk8s).

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

juju relate mongodb-k8s data-integrator

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

juju run data-integrator/leader get-credentials

Save the result listed with uris:.

You can connect to the database with this new URI:

juju ssh --container=mongod mongodb-k8s/0
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.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 the Charmed MongoDB K8Ss’s unit: mongodb-k8s/0. To exit this host type:

exit

You should now be in the shell you started where you can interact with Juju and Kubernetes (Microk8s).

Next Steps

Charmed MongoDB 5 K8s Tutorial - Enable security

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