don't fail on clusters with missing proxies

[fspmarshall]

Allows clusters to be loaded by web UI even if no proxies are currently known.

An error during the loading of a single cluster can cause the whole web UI to err out. Auth server version defaults to "" if no auth servers can currently be loaded, but errors were still being generated if no proxies could be loaded. This PR allows the proxy address and version to also default to "" if they are not loadable.

Fixes #4005

[awly]

Can we use some placeholder strings, like unknown?

[fspmarshall]

Can we use some placeholder strings, like unknown?

I'm hesitant to put placeholder messages in potentially meaningful values, esp since things like unknown are technically valid hostnames. @kimlisa is this something that would be easy to handle at the frontent? Provide some kind of placeholder or message when some cluster info is missing?

[kimlisa]

Can we use some placeholder strings, like unknown?

I'm hesitant to put placeholder messages in potentially meaningful values, esp since things like unknown are technically valid hostnames. @kimlisa is this something that would be easy to handle at the frontent? Provide some kind of placeholder or message when some cluster info is missing?

I agree with @fspmarshall that any value can be a valid hostname.

For the UI handling, @alex-kovoy what do you think? I think it is okay to leave these fields blank. Missing proxy isn't the only scenario that leaves it blank, clusters using older proxies will also display blank (b/c these fields don't exist on versions <4.3). In the client side, we can maybe put a placeholder like "not available"?

What it looks like if proxy url and version returns empty:

[alex-kovoy]

@kimlisa

In the client side, we can maybe put a placeholder like "not available"?

Handling of empty strings on UI side needs to be discussed separately. It needs a broader context. As for this ticket, I agree with Forest, let webapi return an empty string.

[russjones]

@fspmarshall Just a heads up, I just ran into this issue. This line took a few minutes to show up and until then I was getting the same error as above.

DEBU [PROXY:1]   List of known proxies updated: ["7b0db878-ca20-4d70-bcee-3252a327145f"]. services/proxywatcher.go:148

Shouldn't this occur right away at startup? I think this would also cause other problems in term of cluster registering themseleves after process restart.

I think that's what' we're seeing here.

[russjones]

@fspmarshall will create another ticket to address a potential underlying issue causing this.