An egress spell masked a service on the surviving network going down: with
`peerResponded` set only by the DNS and gRPC providers, every other failure fell
back to the HTTP-status heuristic, which answers "nothing replied" for anything
that is not speaking HTTP. A refused connection on the local network was read as
the instance's own loss of egress, so the check was recorded as degraded and the
monitor stayed up.
`peerAnsweredFromError` holds the errno codes that require the target's own stack
to have replied — a refusal, a reset, a TLS handshake that got as far as a
certificate. Http, Port, WebSocket and Docker use it; Http also treats any status
code as an answer, and Docker any status from the daemon. Hardware and PageSpeed
go through Http and inherit it.
`true` is the claim that costs something, since it blames the target, so it is
only set on evidence. Two cases stay conservative and are commented as such: a
ping that draws no echo reply, and a gamedig query that fails, neither of which
can be told apart from the instance losing its egress. Nor can a proxied HTTP
request that fails with no response, where the refusal may be the proxy's.
🔧
When customUpCodes mark an HTTPError as up, parse the response body, apply advancedMatcher.validate, and set status to statusUp && matchResult.ok. Return parsed payload and extracted values to match the success path.
Adds a customUpCodes field to the monitor schema to allow users to specify which HTTP status codes should be treated as UP instead of DOWN. Includes core logic in HttpProvider and unit tests.
Refs #3657
Alex Holliday
Craig Lawson
harsh-aghara