Squid Logs: Does a 407 Followed by 200 Count as a Failure?
Count completed operations separately from authentication exchanges when Squid logs a challenge followed by a successful tunnel.
Suppose a client sends one request without proxy credentials, receives a challenge, and retries successfully. A request log can contain two entries. The person using the application experienced one completed operation.
That is why a log split evenly between TCP_DENIED/407 and TCP_TUNNEL/200 does not automatically establish a fifty-percent failure rate. First determine whether the entries form challenge-and-retry pairs.
Count the thing you actually care about
| Measurement | Count |
|---|---|
| Authentication challenges | Proxy replies requesting authentication |
| Proxy attempts | Individual transactions recorded by the intermediary |
| Completed jobs | Application operations reaching their intended outcome |
Correlate timestamps, client context, destination and any available request identifier. An unauthenticated attempt may have no logged username, while its successful retry does. Concurrent activity means adjacent lines alone are weak evidence that two entries belong together.
Also keep a successful tunnel separate from a successful website operation. CONNECT acceptance establishes the tunnel; the destination can still fail during TLS or return an application error afterward.
Investigate repeated terminal challenges, jobs with no later completion, or a sudden change in exchange count. Those are different from a stable challenge-first client doing exactly what its configuration asks. Suppressing authentication merely to make a dashboard greener would change the service rather than repair the measurement.