Add sanity check at startup to ensure the configured filesystem directories don't overlap for different components

[pracucci]

What this PR does

While answering the question #2698 (reply in thread) I've realized that if you set overlapping local directories for different purposes you could end up with weird behaviour (e.g. alertmanager deleting the alerts store content). These errors are quite difficult to detect, so in this PR I'm proposing to introduce a sanity check to ensure the configured filesystem directories don't overlap for different components (checking only the running components).

Thought: the logic encoded in this new check is non trivial, but that's one more reason why we should encode it instead of letting our users figuring out through a try-and-error process.

Which issue(s) this PR fixes or relates to

N/A

Checklist

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

[pracucci]

I need to improve the checks on the filesystem bucket, because ruler and alertmanager use a different prefix so they don't conflict (and blocks storage could have an optional prefix too).

[colega]

Thanks, LGTM.

I've got just one small nitpick: now we have two completely different paths to validate the bucket config:

• When config is just parsed, we call .Validate() and it checks bucket configs: that is basically ensuring that if two buckets are the same, they should have different prefixes.
• Then your new logic is triggered as part of the SanityCheck module.

Can we move the former call to validateBucketConfigs somewhere near the call to checkFilesystemPathsOvelapping? Maybe checkFilesystemPathsOvelapping should be called from validateBucketConfigs?

Otherwise we have two completely paths for validating two aspects of the same config.

[pracucci]

Can we move the former call to validateBucketConfigs somewhere near the call to checkFilesystemPathsOvelapping? Maybe checkFilesystemPathsOvelapping should be called from validateBucketConfigs?

This is a very good feedback. This new check doesn't need to be a sanity check (it doesn't run anything against the real setup) but it's just a static config check. I moved it to be a function of the Config, like validateBucketConfigs().

[colega]

LGTM! Thanks.