Glossary
Transport Error
A failure below HTTP: the request never produced a complete response.
Definition
A transport error is a probe failure that occurs before an HTTP status could be exchanged - DNS resolution failure, TCP refusal or reset, TLS handshake failure, or a timeout past the probe deadline. It is categorically different from receiving a 4xx or 5xx status.
The problem
Monitoring that collapses “no response” and “server returned 500” into one red dot destroys the distinction between an unreachable service and a reachable-but-failing one - two incidents with different owners, symptoms and fixes.
Why it matters
Transport errors keep their identity in the record, which is what lets a later reader separate an unreachable service from a reachable-but-failing one. Working out where a failure sits needs more than one vantage point, and RELIASTRA runs one today - so a transport error is reported as an observation of the path it probed, not as a verdict about the target.
Practical example
RELIASTRA stores each observation with its outcome: status code and latency when a response arrived; an explicit error type when it did not. Availability counts “no expected response,” so the taxonomy stays visible in every aggregate.
How RELIASTRA approaches it
Probes run under a fixed deadline (15 seconds on public records) with bounded redirect handling, and the security policy can refuse a target before any request leaves - recorded as a policy block, a RELIASTRA-side fact, never as vendor downtime.
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