Detect when proxy host is blocked

[tombeynon]

Some nodes have blocked the rest.cosmos.directory proxy from serving traffic to their domain. This doesn't affect health checks but then fails when the node is used to serve traffic under the proxy. Not sure how best to detect this, potentially just setting the host to the relevant proxy domain when checking the health endpoints?

Offending node:
https://meme-api.kleomed.es/

Marked as rate limited for now so it won't be used unless no non-rate limited nodes are available. No way to fully block it right now (also needs implementing).

[koen84]

Checking status here ? It's the other source of errors i'm getting.