Anatomy
Slack's Jan 4 incident degraded progressively then recovered: for a window, requests failed, then the service came back while clients still showed it down. Only a stateful sequence tests whether a client actually re-establishes after recovery — fail three times, then succeed. Circuit breakers that never half-open stay broken forever.
Source: Slack — 2021-01-04 incident summary · 2021-01-04
Replay it
curl -i https://faultydata.com/r/FD-2026-007
// response appears here
Signature
{Status:0 Headers:map[] Body: Corrupt: Delay:<nil> Flaky:<nil> Sequence:0x4743def06540 Drip:<nil> StallAfter:0 Hang:false Phases:[]}