Handle forward slashes in ruler mapper/manager

[jtlisi]

What this PR does:

• Ensure the Ruler can properly handle rule Namespaces with special characters. E.G. /+<>?

Checklist

• Tests updated
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pstibrany]

I'm not sure I understand the upgrade path. I assume there are already existing rule files. How do we handle those?

[pstibrany]

Suggested change

	level.Warn(m.logger).Log("msg", "unable to remove rule file on disk", "file", existingFile.Name(), "err", err)
	level.Warn(m.logger).Log("msg", "unable to remove rule file on disk", "file", fullFileName.Name(), "err", err)

[jtlisi]

These aren't rule files meant for the storage and persistence of rules. They are temporary files that are loaded by the upstream prometheus manager code for evaluation. They are essentially stateless so no upgrade path is required.

[pracucci]

Shouldn't this be considered a CHANGE, mentioning that when we store rules in the filesystem we now base64 encode the filename?

[jtlisi]

Makes sense

[pracucci]

The main downside of this approach is that the encoded filename is unreadable and makes debugging harder. An alternative may be using url.PathEscape() (as far as % character is not a problem). Same examples:

• Hello > Hello
• Hello world > Hello%20world
• a/b > a%2Fb

[gouthamve]

I like this better. This means the existing file names are same as well.

[jtlisi]

This would only work for POSIX, no Windows. Will that be an issue?

[pracucci]

Sorry to bother you on this, but I think that reading the changelog entry it's not clear why it's a CHANGE. Could you clarify it?

[jtlisi]

I need to give it more thought. I'm starting to think a changelog entry is not needed or if anything it should be labeled a BUGFIX since it aligns Cortex with expected behavior.

[pracucci]

Thanks @jtlisi for addressing my feedback. LGTM!