JAAS: Internal Model Migration

This document briefly covers how to migrate a model between two controllers within JAAS.

JIMM can have multiple controllers connected to it, where more than 1 controller has access to the same cloud. When a model is requested on such a cloud, JIMM will randomly select an appropriate controller.

The below is useful if you want to move the model to a specific controller.

Prerequisites

  • A basic understanding of Juju model migrations, see the docs.

  • A running JAAS with with multiple controllers attached, see the tutorial for deploying JAAS.

  • Administrator permissions for JAAS, so our how-to.

Connecting multiple controllers to JAAS can be accomplished adding LXD controllers as described in our how-to.

1. Identify the new controller

JIMM does not currently expose information about which underlying controller hosts a specific model. This information is stored in JIMM’s database but the controller info returned when running juju show-model <model-name> is JIMM’s UUID and name, hiding the underlying controller information.

The following command will show you all the controllers connected to JIMM.

jimmctl list-controllers

Currently to identify where the model is hosted, you must have access to the controllers connected to JIMM and switch to those controllers in turn, and run juju models until you identify the correct controller. This may be improved in the future for users of jimmctl to identify the underlying controller for a model.

Identify the controller you want to migrate to, only the name is necessary.

2. Migrate your model

The following command will migrate a model named my-model to the desired controller, in this case called my-controller.

MODEL_NAME=my-model
MODEL_UUID=$(juju show-model $MODEL_NAME --format yaml | yq .$MODEL_NAME.model-uuid)
jimmctl migrate my-controller $MODEL_UUID

This will start the model migration process. You can now monitor the progress of the migration with juju status and juju debug-log.

Once the model has been successfully migrated, run the following command to update JIMM with the new controller information for the model.

jimmctl update-migrated-model my-controller $MODEL_UUID

This will update JIMM’s internal state to locate the model on the specified controller.

At this point you can run juju status to see the model info.

3. Handling failed migration

If the model migration fails, then no further user input is required and the model should continue to exist on the original controller.

To inspect the reason for failure, consult the output from juju debug-log and juju status.