Get a Charmed MongoDB up and running

This is part of the Charmed MongoDB K8s Tutorial. Please refer to this page for more information and the overview of the content.

Deploy

To deploy Charmed MongoDB K8s, 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-k8s --channel 6/beta

Juju will now fetch Charmed MongoDB and begin deploying it to the Kubernetes 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 pods 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    microk8s/localhost  3.1.6   unsupported  15:33:40Z

App          Version  Status  Scale  Charm        Channel  Rev  Address        Exposed  Message
mongodb-k8s           active      1  mongodb-k8s  6/beta    37  10.152.183.20  no

Unit            Workload  Agent  Address      Ports  Message
mongodb-k8s/0*  active    idle   10.1.42.137
Model     Controller  Cloud/Region        Version  SLA          Timestamp
tutorial  overlord    microk8s/localhost  3.1.6   unsupported  15:33:41Z

To exit the screen with watch -n 1 -c juju status, run 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, the operator user is our admin user in Charmed MongoDB. 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 operator 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.mongo.

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:

mongo://<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 operator user to connect to MongoDB. Use operator 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-k8s/leader get-password

Running the command should output:

Running operation 1 with 1 task
  - task 2 on unit-mongodb-k8s-0

Waiting for task 2...
password: INIsjvJmDsuaPY2Rta0fPzas0zVKO5AJ

Use the value of password under the result: password:

export DB_PASSWORD=$(juju run mongodb-k8s/leader get-password  | grep password |  awk '{print $2}')

Retrieving the hosts: In this case we are connecting to mongo inside mongodb-k8s/0

Set the variable HOST_IP to the IP address to mongodb-k8s-0.mongodb-k8s-endpoints:

export HOST_IP="mongodb-k8s-0.mongodb-k8s-endpoints"

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-k8s. Use mongodb-k8s as the replica set name.

export REPL_SET_NAME="mongodb-k8s"

Generate the MongoDB URI

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

export URI=mongodb://$DB_USERNAME:$DB_PASSWORD@$HOST_IP:27017/$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 K8s as mongo. To access the unit hosting Charmed MongoDB K8S, ssh into it pod:

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

Note if at any point you’d like to leave the unit hosting Charmed MongoDB K8S, type: exit.

While ssh’d into mongodb-k8s/0 unit, we can access mongo, using the URI that we saved in the step Generate the MongoDB URI.

mongosh <URI>

You should now see:

Current Mongosh Log ID: <your connection id>
Connecting to:          mongodb://<credentials>@mongodb-k8s-0.mongodb-k8s-endpoints:27017/admin?replicaSet=mongodb-k8s&appName=mongosh+2.0.1
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/


To help improve our products, anonymous usage data is collected and sent to MongoDB periodically (https://www.mongodb.com/legal/privacy-policy).
You can opt-out by running the disableTelemetry() command.

------
   The server generated these startup warnings when booting
   2023-11-09T06:40:15.609+00:00: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine. See http://dochub.mongodb.org/core/prodnotes-filesystem
   2023-11-09T06:40:16.238+00:00: vm.max_map_count is too low
------

mongodb-k8s [primary] admin> 

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

admin   0.000GB
config  0.000GB
local   0.000GB

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

use test-db

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

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

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

{
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1699533481, i: 1 }),
    signature: {
      hash: Binary.createFromBase64("/cRpojgyhSuF0UIS8kM0GZhAPss=", 0),
      keyId: Long("7299439113034268679")
    }
  },
  operationTime: Timestamp({ t: 1699533481, i: 1 })
}

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 the mongodb-k8s/0 unit.
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 Kubernetes.

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 Steps

Charmed MongoDB K8s Tutorial - Managing your units