Github's incidents have individual RCAs but nothing explaining the collective
We haven't received an RCA for yesterday yet. GitHub mentioned in the resolution note that it had committed to producing one. The only public information regarding the cause is an update at 19:13 UTC in which they stated that they had partially disabled authentication token retries and had noticed an improvement; this corresponds with Copilot auth being the last service to recover, about four hours after the other seven services had been mitigated.
Well worth reading the resolutions for the rest of this month. The account of the Aug 6 Actions incident is particularly specific compared to most public writeups. When a routine deployment was made to an internal Actions service, an existing weakness in terms of capacity and concurrency came to light, the pods were replaced and the remaining capacity was saturated as a result of which the services crashed and a cascade of failures spread across the clusters. There was then a second phase in which a latent bug caused runners to be assigned jobs that were no longer valid and so they ended up retrying those invalid jobs rather than picking up real work. At peak times 71% of the workflow runs failed due to infrastructure errors.
Although the pull request of 24 July is the better piece of writing, a backfill cancellation came across what they refer to as a misundertood Vitess codepath, as a result of which the backing table was dropped and a dangling vschema reference was left behind. That is what blameless should mean, identifying a gap in the tooling rather than blaming a person.
The line that I had not anticipated appeared in the Aug 6 Pages writeup, where it was stated that the incident had not been fully picked up by their availability metrics and that they are altering the way Pages availability is measured so that it will be reflected in the future. Approximately 128,000 deployments failed to be processed during a period which their own SLI had not recorded.
There are seventeen incidents listed on the status page from August 1st to August 18th; each of them will have its own root cause analysis, none of which will account for the seventeen. That's the real analysis needed imo.