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Introduction

It's often common practice that a juju developer needs to test out new juju code on machines that are not the same operating system or architecture to that of their current host. Alternatively in this workflow it is common place to want to want to perform Juju upgrades.

Examples of this would be:

  • ubuntu/amd64 -> ubuntu/s390x
  • ubuntu/amd64 -> centos/amd64
  • macos/amd64 -> ubuntu/amd64
  • macos/arm64 -> ubutnu/amd64

Doing this has been difficult in the past but with changes to the juju Makefile we can now build simple streams for multiple platforms and versions.

How it works

Bootstrapping

We start by telling the juju build systems that we would like a local simple streams repository created for a given set of Go style os/arch pairs. For this example we would like a simple stream of our development changes that have artifacts for linux/amd64 and linux/arm64.

The juju build system is going place artifacts in a simplestream directory. You can optionally specify where you would like this directory to be by exporting JUJU_METADATA_SOURCE in your environment or simply let the build system choose for you.

export JUJU_METADATA_SOURCE=<local_simplestreams_path>

This is created by running:

AGENT_PACKAGE_PLATFORMS="linux/amd64 linux/arm64" make simplestreams

This process will build all the juju agent binaries for the platforms specified above and package them into a simple streams repository.

The end of the output for this make command will also provide the user with an export statement that the user should run to help the juju bootstrap command automatically find this local simple streams repository. Example output:

export JUJU_METADATA_SOURCE="...."

You can ignore the above export requirement if you have previously done this in a previous step.

You can now bootstrap using this simple streams repository using the usual:

juju bootstrap cloudx

Note: You may need to specify additional bootstrap-constrains to help juju choose the correct architecture.

Upgrading

Often once we have a bootstrapped controller we want to upgrade the controller for testing or time reasons.

To do this we now need to run the make simplestreams target again but this time we also want to supply the build system with a build number.

JUJU_BUILD_NUMBER=1 AGENT_PACKAGE_PLATFORMS="linux/amd64 linux/arm64" make simplestreams

Note: A key way to tell if this has worked is by looking at the output of the command to confirm the new version is being used.

You will also be prompted to export the JUJU_METADATA_SOURCE again. This step can safely be ignored if previously done from a previous step.

Next we need to get these new version artifacts on to the juju controller that we want to upgrade.

juju sync-agent-binary --version=<version>

Where <version> is the Juju version we are upgrading to including the build number from above.

We can now perform the upgrade using:

juju upgrade-controller --agent-version <version>

Where <version> is the Juju version we are upgrading to including the build number from above.

Current limitations & future changes

  • Does not support oci artifacts including upgrading of OCI deployed controllers and agents.
  • Would like to integrate work by @hpidcock for a simplestreams server that continuously builds and updates.