Upgrade ignores '--agent stream proposed' (2.4.2)

[Christopher Lee]

As found by the functional test 'nw-upgrade-juju-amd64-lxd' the command 'juju upgrade --agent-stream proposed' is ignored and juju looks in 'released'.

We can see that in these logs and example[1].
I can confirm that the generated streams for the test include a xenial 2.4.3 agent in the proposed stream but not released (hence the failure to upgrade).

[1] https://pastebin.canonical.com/p/NG8PRCg26f/

[Ian Booth (wallyworld)]

The issue appears to be the the upgrade-juju command correctly processes the requested agent-stream argument and finds the agent binaries in the right place and handles the controller upgrade.

However, as each machine agent is notified that they should upgrade, at that point these agents don't have access to the requested stream passed in via the CLI arg - they just see the model config agent-stream value. So they look in the wrong place.

The work around is to continue to use the model config agent stream as was needed before the CLI arg was introduced.

[Ian Booth (wallyworld)]

Maybe I'm wrong because if the controller can get the agent binaries initially, they should then be cached and subsequent lookups from agents will find the cached copy, even though the agents may specify just the released stream.