TooManyRedirects and BlockedAddress: Two Failure Codes Nobody Expects

Beyond the obvious five

Timeout, connection refused, DNS failure, a TLS problem, an unexpected status code — those five cover most outages and mean roughly what they sound like. Two other failure codes show up rarely enough that they're worth explaining before the first time you see one.

TooManyRedirects

The check followed redirect after redirect and never reached a final page. This is almost never a real outage — it's a redirect loop, usually introduced by a caching rule, a load balancer misconfiguration, or an http → https redirect that accidentally points back at http. The site "loading forever" in a browser and this failure code are usually the same bug, seen from two different angles.

BlockedAddress

The check refused to even attempt the request, because the address it resolved to isn't one we're willing to call — a private or internal IP range, for instance. This one isn't a sign anything is wrong with your site; it's a safety rule that stops a monitor from being pointed at internal infrastructure it has no business reaching. If you see it, the fix is almost always the URL being checked, not the server behind it.

Why these get their own names instead of "Unknown"

A failure that's actually a redirect loop and a failure that's actually a safety block need completely different fixes. Folding both into a generic "something went wrong" would send whoever reads the alert down the wrong path first — these two exist as distinct codes for the same reason timeout and DNS failure do.