How to perform a minor upgrade on a sharded cluster
This feature is only available on specific revisions in Charmed MongoDB K8s 6/stable, listed in Minor version upgrade > Supported revisions.
If you wish to upgrade to/from a different, non-supported revision, then perform a cluster migration via backup.
Here is a summary of the steps to perform a minor upgrade on a sharded cluster:
- Determine your current revision
- Determine new revision
- Upgrade config-server
- Upgrade shards
- Upgrade mongos applications
Step 1: Determine your current revision
Find determine your current revision:
juju status | grep <app-name> | head -1 | awk '{print $5}'
If your current revision is not in the list of supported revisions for upgrades, then you must perform a cluster migration via backup.
If the upgrade is unsuccessful, you will need this revision number to roll back your application.
Step 2: Determine new revision
Choose a revision to upgrade to from the list of available revisions to upgrade to. By the end of your upgrade, the config-servers and shards must all be on the same revision.
Step 3: Upgrade config-server
To upgrade your config-server, follow the instructions in how to upgrade a replica set
Do not proceed if this step was not successful. If your upgrade failed, roll back the cluster.
Step 4: Begin upgrade
If you succeeded in upgrade your config-server in Step 3, you may proceed to upgrade your shards.
Upgrade each shard one at a time. Start by upgrading the first shard and follow the instructions in how to upgrade a replica set.
Upgrade the next shard only when the current upgrade succeeds - i.e. all units show active and idle statuses.
Do not proceed if an upgrade of a shard fails. If an upgrade fails, rollback the entire cluster.
Step 5: Upgrade mongos applications
Next, upgrade any integrated mongos applications by following the Charmed Mongos K8s documentation on How to perform a minor version upgrade.