loki.api.url should discard any provided /loki/api/v1/push

[simondeziel]

When configuring integration with Loki, one provides LXD with the URL to Loki's API. Since a URL can include the path, a user may do lxc config set loki.api.url=http://10.76.66.141:3100/loki/api/v1/push. The problem is that LXD unconditionally appends /loki/api/v1/push to the provided URL resulting in bogus HTTP POSTs to http://10.76.66.141:3100/loki/api/v1/push/loki/api/v1/push.

The doc on loki.api.url is pretty succinct so I think it's a fair mistake for someone to do, at least I think I did when implementing the charm because the Loki integration lib returns http://${hostname|ip}:3100/loki/api/v1/push and I feed that directly to LXD. While I could fix the charm, I think the LXD side should be improved. Either by dropping any provided /loki/api/v1/push suffix or by rejecting the value as bogus.

[monstermunchkin]

I prefer dropping the /loki/api/v1/push if provided by the user.

[tomponline]

My preference would be to improve the docs and explain that LXD will add the /loki/api/v1/push to the URL, otherwise this url setting will be a special case compared to other ones (such as the ones we use for interacting with external auth providers, where we also append certain paths to the end).

Also if we start stripping stuff from the URL that the user provides we don't know if they do infact need that, perhaps to get through a reverse proxy to their loki server.