Charmed MongoDB Tutorials > Deploy a sharded cluster > 2. Deploy MongoDB
Deploy MongoDB
Sharding is MongoDB’s solution to horizontal scaling. MongoDB’s documentation describes horizontal scaling in databases as the process of “ dividing a large database into smaller, more manageable pieces (called shards) and then distributing the shards across multiple machines.”
In Charmed MongoDB K8s, we create sharded clusters by deploying several MongoDB applications as individual cluster components, and then integrating them. This part of the tutorial will guide you through a practical example of a sharded cluster deployment.
Summary
- Deploy cluster components, i.e. shards and a config server
- Integrate shards with the config server
Deploy cluster components
The first step to creating your sharded cluster is to deploy cluster components.
If you run juju deploy mongodb-k8s without specifying a role, the application will be automatically deployed as a replica set. To deploy a sharded cluster, we must manually define the roles of the individual cluster components:
juju deploy mongodb-k8s --config role="config-server" config-server
juju deploy mongodb-k8s --config role="shard" shard0
juju deploy mongodb-k8s --config role="shard" shard1
For a deeper explanation about the difference between replication and sharding see Explanation | Replication vs. sharded cluster deployments.
Use juju status --watch 1s to wait until these components are ready.
When the components are ready, your output should look similar to the example below:
Model Controller Cloud/Region Version SLA Timestamp
tutorial overlord microk8s/localhost 3.1.7 unsupported 19:06:51+01:00
App Version Status Scale Charm Channel Rev Exposed Message
config-server blocked 1 mongodb 6/stable 158 no Missing relation to shard(s).
shard0 blocked 1 mongodb 6/stable 158 no Missing relation to config-server.
shard1 blocked 1 mongodb 6/stable 158 no Missing relation to config-server.
Unit Workload Agent Address Ports Message
config-server/0* blocked idle 10.56.148.138 Missing relation to shard(s).
shard0/0* blocked idle 10.56.148.149 Missing relation to config-server.
shard1/0* blocked idle 10.56.148.60 Missing relation to config-server.
All statuses are blocked because the shards are not yet integrated/related with the config-server.
Integrate shards with the config server
Juju integrations are a way to connect applications such that they can communicate with one another through compatible endpoints.
To integrate the shards with the config server, run
juju integrate config-server:config-server shard0:sharding
juju integrate config-server:config-server shard1:sharding
You’ll know your cluster is active and ready when juju status --watch 1s shows all apps as active.
Model Controller Cloud/Region Version SLA Timestamp
tutorial overlord microk8s/localhost 3.1.7 unsupported 19:15:36+01:00
App Version Status Scale Charm Channel Rev Exposed Message
config-server active 1 mongodb 6/stable 158 no
shard0 active 1 mongodb 6/stable 158 no
shard1 active 1 mongodb 6/stable 158 no
Unit Workload Agent Address Ports Message
config-server/0* blocked idle 10.56.148.138 Primary
shard0/0* blocked idle 10.56.148.149 Primary
shard1/0* blocked idle 10.56.148.60 Primary
Next step: 3. Access a sharded cluster