Charmed MongoDB Tutorial - Deploy MongoDB - 6

Get a Charmed MongoDB up and running

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

Deploy

To deploy Charmed MongoDB, all you need to do is run the following command, which will fetch the charm from Charmhub and deploy it to your model:

juju deploy mongodb --channel 6/beta

Juju will now fetch Charmed MongoDB and begin deploying it to the LXD cloud. This process can take several minutes depending on how provisioned (RAM, CPU,etc) your machine is. You can track the progress by running:

watch  -n 1 -c juju status

This command is useful for checking the status of Charmed MongoDB and gathering information about the machines hosting Charmed MongoDB. Some of the helpful information it displays include IP addresses, ports, state, etc. The command updates the status of Charmed MongoDB every second and as the application starts you can watch the status and messages of Charmed MongoDB change. Wait until the application is ready - when it is ready, watch -n 1 -c juju status will show:

Model     Controller  Cloud/Region         Version  SLA          Timestamp
tutorial  overlord    localhost/localhost  3.1.6   unsupported  11:24:30Z

App      Version  Status  Scale  Charm    Channel   Rev  Exposed  Message
mongodb           active      1  mongodb  6/beta   140  no

Unit        Workload  Agent  Machine  Public address  Ports      Message
mongodb/0*  active    idle   0        10.23.62.156    27017/tcp

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

To exit the screen with watch -n 1 -c juju status, enter Ctrl+c.
You can also add --color parameter to the command. watch -n 1 -c juju status --color

Access MongoDB

! Disclaimer: this part of the tutorial accesses MongoDB via the operator user. Do not directly interface with the admin user in a production environment. In a production environment always create a separate user and connect to MongoDB with that user instead. Later in the section covering Relations we will cover how to access MongoDB without the admin user.

The first action most users take after installing MongoDB is accessing MongoDB. The easiest way to do this is via the MongoDB shell, with mongo. You can read more about the MongoDB shell here. For this part of the Tutorial we will access MongoDB via mongo. Fortunately there is no need to install the Mongo shell, as mongo is already installed on the units hosting the Charmed MongoDB application as charmed-mongodb.mongosh.

MongoDB URI

Connecting to the database requires a Uniform Resource Identifier (URI), MongoDB expects a MongoDB specific URI. The URI for MongoDB contains information which is used to authenticate us to the database. We use a URI of the format:

mongodb://<username>:<password>@<hosts>/<database name>?replicaSet=<replica set name>

Connecting via the URI requires that you know the values for username, password, hosts, database name, and the replica set name. We will show you how to retrieve the necessary fields and set them to environment variables.

Retrieving the username: In this case, we are using the admin user to connect to MongoDB. Use admin as the username:

export DB_USERNAME="operator"

Retrieving the password: The password can be retrieved by running the get-password action on the Charmed MongoDB application:

juju run mongodb/leader get-password

Running the command should output:

Running operation 5 with 1 task
  - task 6 on unit-mongodb-0

Waiting for task 6...
password: 9JLjd0tuGngW5xFKWWbo0Blxyef0oGec

Use the password under the result: password:

export DB_PASSWORD=$(juju run mongodb/leader get-password  | grep password|  awk '{print $2}')

Retrieving the hosts: The hosts are the units hosting the MongoDB application. The host’s IP address can be found with juju status:

Model     Controller  Cloud/Region         Version  SLA          Timestamp
tutorial  overlord    localhost/localhost  3.1.6  unsupported  11:31:16Z

App      Version  Status  Scale  Charm    Channel   Rev  Exposed  Message
mongodb           active      1  mongodb  6/beta   140  no       Replica set primary

Unit        Workload  Agent  Machine  Public address  Ports      Message
mongodb/0*  active    idle   0        <host IP>    27017/tcp  Replica set primary

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

Set the variable HOST_IP to the IP address for mongodb/0:

export HOST_IP=$(juju exec --unit mongodb/0 -- hostname -I | xargs)

Retrieving the database name: In this case we are connecting to the admin database. Use admin as the database name. Once we access the database via the MongoDB URI, we will create a test-db database to store data.

export DB_NAME="admin"

Retrieving the replica set name: The replica set name is the name of the application on Juju hosting MongoDB. The application name in this tutorial is mongodb. Use mongodb as the replica set name.

export REPL_SET_NAME="mongodb"

Generate the MongoDB URI

Now that we have the necessary fields to connect to the URI, we can connect to MongoDB with charmed-mongodb.mongosh via the URI. We can create the URI with:

export URI=mongodb://$DB_USERNAME:$DB_PASSWORD@$HOST_IP/$DB_NAME?replicaSet=$REPL_SET_NAME

Now view and save the output of the URI:

echo $URI

Connect via MongoDB URI

As said earlier, mongo is already installed in Charmed MongoDB as charmed-mongodb.mongosh. To access the unit hosting Charmed MongoDB, ssh into it:

juju ssh mongodb/0

Note if at any point you’d like to leave the unit hosting Charmed MongoDB, enter exit.

While sshd into mongodb/0, we can access mongo, using the URI that we saved in the step Generate the MongoDB URI.

charmed-mongodb.mongosh <saved URI>

You should now see:

Current Mongosh Log ID: 6389e2adec352d5447551ae0
Connecting to:    mongodb://<credentials>@10.23.62.156/admin?replicaSet=mongodb&appName=mongosh+1.6.1
Using MongoDB:		6.0.6-5
Using Mongosh:		2.0.1
mongosh 2.0.2 is available for download: https://www.mongodb.com/try/download/shell

For mongosh info see: https://docs.mongodb.com/mongodb-shell/

mongodb [primary] admin>

You can now interact with MongoDB directly using any MongoDB commands. For example entering show dbs should output something like:

admin   172.00 KiB
config  120.00 KiB
local   404.00 KiB

Now that we have access to MongoDB we can create a database named test-db. To create this database enter:

use test-db

Now lets create a user called testUser with read/write access to the database test-db that we just created. Enter:

db.createUser({
  user: "testUser",
  pwd: "password",
  roles: [
    { role: "readWrite", db: "test-db" }
  ]
})

You can verify that you added the user correctly by entering the command show users into the mongo shell. This will output:

[
  {
    _id: 'test-db.testUser',
    userId: new UUID("6e841e28-b1bc-4719-bf42-ba4b164fc546"),
    user: 'testUser',
    db: 'test-db',
    roles: [ { role: 'readWrite', db: 'test-db' } ],
    mechanisms: [ 'SCRAM-SHA-1', 'SCRAM-SHA-256' ]
  }
]

Feel free to test out any other MongoDB commands. When you’re ready to leave the MongoDB shell you can just type exit. Once you’ve typed exit you will be back in the host of Charmed MongoDB (mongodb/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 LXD.

Note: if you accidentally exit one more time you will leave your terminal session and all of the environment variables used in the URI will be removed. If this happens redefine these variables as described in the section that describes how to create the MongoDB URI.

Next step

Charmed MongoDB Tutorial - Managing units