Charmed MongoDB Tutorial (replica set) | 6. Integrate with other applications

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Charmed MongoDB Tutorials > Deploy a replica set > 6. Integrate with other applications

Integrate MongoDB with other applications

Juju integrations, previously known as “relations”, 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. The best practice is to connect to MongoDB via a specific user rather than the admin user, like we did earlier in this tutorial.

In this part of the tutorial, you will learn how to integrate MongoDB with another charm, access an integrated database, and manage users via integrations.

Summary

Deploy the 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.

When deploying the Data Integrator charm, we will set a name for a database called test-database using juju’s config flag:

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

The expected output:

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

Integrate with 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.

Integrate the two applications with:

juju integrate 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  3.1.6   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 data-integrator/leader get-credentials

This should output something like:

​​Running operation 21 with 1 task
  - task 22 on unit-data-integrator-0

Waiting for task 22...
mongodb:
  database: test-database
  endpoints: 10.63.102.106,10.63.102.223
  password: kXOOyTbccn2cXs3kokOqPJz3Mu9g3a5g
  replset: mongodb
  uris: mongodb://relation-2:kXOOyTbccn2cXs3kokOqPJz3Mu9g3a5g@10.63.102.106,10.63.102.223/test-database?replicaSet=mongodb&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 data-integrator/leader get-credentials 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.mongosh "<uri copied from get-credentials>"

Make sure you wrap the URI in quotation marks ( "" ) 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 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()

Return to original shell

Leave the MongoDB shell by typing exit.

You will be back in the host of Charmed MongoDB (mongodb/0). Exit this host by typing exit again.

You should now be at the original shell where you can interact with Juju and LXD.

Remove the user

Removing the integration automatically removes the user that was created with it.

To remove the integration (and therefore the user), run the following command:

juju remove-relation mongodb data-integrator

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

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

Make sure you wrap the URI in quotation marks ( "" ) 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.

This is expected, since the user no longer exists.

Return to original shell

Leave the MongoDB shell by typing exit. You will be back in the host of Charmed MongoDB (mongodb/0). Exit this host by typing exit again.

You should now be at the original shell where you can interact with Juju and LXD.

Recreate the user

If you wanted to recreate the user we just removed, all you would need to do is integrate the two applications again:

juju integrate 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 data-integrator/leader get-credentials

Save the result listed with uris:.

You can connect to the database with this new URI:

juju ssh mongodb/0
charmed-mongodb.mongosh "<uri copied from get-credentials>"

Note: be sure you wrap the URI in quotation marks (") 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.

Return to original shell

Leave the MongoDB shell by typing exit. You will be back in the host of Charmed MongoDB (mongodb/0). Exit this host by typing exit again.

You should now be at the original shell where you can interact with Juju and LXD.

Next step: 7. Enable security

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This can be updated to: Wait for juju status --watch 1s so new learners also learn some new parameters and arguments of juju cli and expand their knowledge a bit more in this tutorial.

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