How to upgrade¶

Major version upgrade¶

This refers to an upgrade from MongoDB 6 to MongoDB 8.

After having upgraded your sharded cluster with (see MongoDB - How to upgrade), you can proceed to deploy a new Mongos VM application (see: Mongos - How to deploy)) and relate it with the config-server.

Please note that Mongos 6 and MongoDB 8 are not compatible, so you have to update them separately.

Please also note that Mongos 8 is released on Ubuntu 24.04 base, which means the host application has to be deployed as well using an Ubuntu 24.04 base.

Minor version upgrade¶

This refers to an upgrade between different charm revisions of Mongos 8.

Supported revisions¶

Only upgrade from these supported revisions in a production environment.

VM:

Revision 24
Revision 54

K8s:

Revision 17
Revision 43

Upgrade steps¶

Ensure your MongoDB deployment is healthy (active and idle), and not performing any long-running operations such as creating a backup.

Step 1: Pre-refresh check¶

Before refreshing, the charm needs to perform some preparatory tasks to define the refresh plan.

Run the pre-refresh-check action against the leader unit of your Mongos application:

juju run mongos/leader pre-refresh-check

K8s

juju run mongos-k8s/leader pre-refresh-check

Warning

Do not proceed if this action is unsuccessful.

If the action succeeds, copy down the rollback command. Keep the command available in case you need to roll back.

Step 2: Determine your current revision¶

Find your current revision with juju status:

juju status | grep mongos | head -1 | awk '{print $6}'

K8s

juju status | grep mongos-k8s | head -1 | awk '{print $6}'

Caution

If your current revision is not in the list, then upgrade is not supported.

In the case that your upgrade is not successful, you will need this revision number to roll back your application.

Step 3: Determine new revision¶

Choose a revision to upgrade to from the list of available revisions to upgrade to

Step 4: Upgrade the router¶

Using the revision from Step 3, upgrade your application

juju refresh mongos --revision=<revision number>

K8s

juju refresh mongos-k8s --revision=<revision number>

The upgrade should begin, and upgrade all deployed mongos routers. You can watch and wait for the upgrade to succeed with juju status --watch 1s.

If all units show active and idle statuses after upgrading, then your upgrade succeeded.

If your upgrade failed, then juju status will show that the unit is blocked with the message Unhealthy after refresh. You can do the following:

Recommended: Wait for 5-10 minutes to see if the router can heal itself
Recommended: Roll back. Use the rollback command from the pre-refresh check.
Not Recommended: Force an upgrade by running juju run mongos/leader force-refresh-start. Please note this can break your database and is not recommended.