Independent review on PR #2362 caught: the dead-agent classifier at
a2a_proxy.go included 502/503/504/524 but missed the rest of the CF
origin-failure family (521/522/523), which are MORE indicative of a
dead EC2 than 524:
- 521 "Web server is down" — CF can't open TCP to origin (most direct
dead-EC2 signal; fires when the workspace EC2 has been terminated
and CF still has the CNAME pointing at it).
- 522 "Connection timed out" — TCP didn't complete in ~15s (typical
of SG/NACL flap or agent process hung on accept).
- 523 "Origin is unreachable" — CF can't route to origin (DNS gone,
network path broken).
Pre-fix any of these would propagate as-is to the canvas and the user
would see a 5xx without the reactive auto-restart firing — exactly
the SaaS-blind class of failure PR #2362 was meant to close.
Refactor: extracted isUpstreamDeadStatus(int) helper so the matrix is
in one place, with TestIsUpstreamDeadStatus locking in 18 status
codes (7 dead, 11 not-dead including 520 and 525 which look CF-shaped
but indicate different failures).
Also tightened TestStopForRestart_NoProvisioner_NoOp per the same
review: now uses sqlmock.ExpectationsWereMet to assert the dispatcher
doesn't touch the DB on the both-nil path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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