Error out when user provides own simplestreams url with no matches

[Simon Richardson]

If a user defines their own simplestreams agent-metadata-url and we don't find a matching binary, then we fallback to one in the $PATH. This is very confusing and not what I expected to happen.

Instead we should fail hard and explain that what they've provided doesn't match what we expect.

[Ian Booth (wallyworld)]

This is by design - simplestreams uses a list of search paths. Just because a user provides their own URL, doesn't mean they always want to use *only* the entries from that URL. They may want to override only a specific version etc.

Is there are reason why the established behaviour is wrong? It's been documented that way since the start so we'll need to be careful if we want to change it.

[Simon Richardson (simonrichardson)]

I find the behavior confusing, if I do, others surely will!

Let's put it another way if you pass in both an agent-metadata-url and an agent-version I'm pretty sure you shouldn't be looking elsewhere! You're telling Juju to look here for the agent-version and it's not there and you go look somewhere else, then we bootstrap, but we do it with something they don't want.

We didn't find the agent in the metadata, we should error out fast rather than bootstrap with something they didn't want.

[Ian Booth (wallyworld)]

Think of it as like adding /usr/local/bin to your path. You don't want it to error and stop searching but rather move on to say /usr/bin if what you ask for isn't there.

A common use case is when someone wants to just test out a new focal ami - they don't want to have to copy the entire upstream simplestreams set of files just to plug in an override.

[Juan M. Tirado (tiradojm)]

Old issue. Reopen if needed.

[Launchpad Janitor (janitor)]

[Expired for Canonical Juju because there has been no activity for 60 days.]