The regression test `docs/plan/jobs-handling-recoverable-error.md`
§Testing asks for: assert the run reaches Paused, that `error_message`
names the cause, and that it does so in bounded time rather than
hanging.
## The endpoint has to HANG, not refuse
`s3_stub` already existed and points at `127.0.0.1:9999`, where nothing
listens. That connection is REFUSED — ECONNREFUSED, immediately — and
that path was never broken. A test built on it would pass with no
timeout configured anywhere, which is worse than no test: it would read
as coverage of exactly the failure it cannot see.
So `s3_blackhole` points at `192.0.2.1`, TEST-NET-1 (RFC 5737),
reserved for documentation and guaranteed unrouted. A SYN goes
unanswered — no RST, no ICMP — which is the failure that used to hang
until the OS abandoned TCP retransmission ~15 minutes later, with the
job neither running nor failed the whole time.
Ed's suggestion, and it is the right fixture: a server that never
answers is reproducible in a way that unplugging a cable is not.
## The load-bearing assertion is `duration`
Every other assert in the file would also pass against the old hanging
behaviour, given fifteen minutes. `duration < 120000` is the only one
that fails if the bound is ever removed. The threshold is deliberately
loose — three orders of magnitude from the failure it guards, so a slow
runner cannot make it flaky.
## Why it is safe in the shared suite
The run fails at `target.initialize()`, which is BEFORE
`migration_readonly` is engaged, so this file cannot leave the server
read-only for whatever runs next. A mid-copy failure would have held
the freeze — that is why this shape was chosen.
Teardown is mandatory rather than tidy: `open_or_start` picks up the
latest non-terminal row, so a Paused row left behind would be RESUMED
by the next `backend_migration` trigger in the suite, silently
retargeting an unrelated test at the black hole. The file cancels its
own run and asserts the row reached Cancelled.
Placed second-to-last. It is the slowest file in the suite by design —
it waits out an unreachable endpoint to prove the wait is bounded — so
that cost lands after everything else has reported. Azurite stays last
for the reason its own comment gives.
Not yet executed: the suite tears down containers and Ed usually has a
run in flight.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Edouard Vanbelle
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