Anatomy
On 2021-06-08 a customer config change triggered an undiscovered bug and ~85% of requests globally returned errors for about an hour. Real degradation is not a binary outage: some requests succeed, some fail, latencies stretch. This composite specimen returns 503 ~85% of the time with normal success the remainder — the pattern that breaks "is it up?" health checks while users see failures.
Source: Fastly summary of June 8 outage · 2021-06-08
Replay it
curl -i https://faultydata.com/r/FD-2026-002// response appears hereSignature
{Status:0 Headers:map[] Body: Corrupt: Delay:<nil> Flaky:<nil> Sequence:<nil> Drip:<nil> StallAfter:0 Hang:false Phases:[{Weight:85 Signature:{Status:503 Headers:map[] Body:{"error":"Error 503 Service Unavailable","detail":"Varnish cache server"} Corrupt: Delay:<nil> Flaky:<nil> Sequence:<nil> Drip:<nil> StallAfter:0 Hang:false Phases:[]}} {Weight:15 Signature:{Status:200 Headers:map[] Body: Corrupt: Delay:<nil> Flaky:<nil> Sequence:<nil> Drip:<nil> StallAfter:0 Hang:false Phases:[]}}]}