Exercise 2: Why Rollback Is More Likely Needed in a Runbook Than Routine Documentation — Possible Solution ==================================================================== WHAT THIS CHAPTER SAYS ------------------------------ Per this chapter, "a runbook is disproportionately likely to be used exactly when something is already going wrong, which makes hitting a genuine failure partway through more likely, not less, compared to routine documentation used under calm conditions." WHY THE CIRCUMSTANCES OF USE ARE DIFFERENT ------------------------------ A runbook, by its own nature (per Chapter 2's own definition), exists to guide action during a specific problem - it's reached for specifically because something is already broken or behaving abnormally. Routine documentation, like a KB article consulted out of general curiosity or for planning purposes, is typically read under calm, stable conditions, where the underlying system is behaving normally and there's no active problem already in progress. WHY THIS MEANS THE STARTING CONDITIONS THEMSELVES ARE LESS PREDICTABLE ------------------------------ Because a runbook is invoked precisely when something is already wrong, the system's actual state at the moment the runbook begins is less predictable than it would be under calm conditions - there may be partial damage already present, unusual load, or side effects from whatever originally triggered the problem. A procedure written assuming a clean, stable starting point is more likely to encounter something it didn't anticipate exactly because the starting point itself is already abnormal. WHY THIS DIRECTLY INCREASES THE ODDS OF A MIDWAY FAILURE ------------------------------ A procedure executed against an already-degraded or unusual system has more opportunities to hit an unexpected condition partway through than the same procedure executed against a healthy, predictable one. This is precisely why rollback - a plan for what to do when something goes wrong mid-procedure - matters more for runbooks specifically, not as a general best practice applicable equally everywhere. WHY THIS WORKS AS AN ANSWER ------------------------------ It quotes the chapter's own reasoning, explains why the circumstances under which a runbook gets used differ from routine documentation, and explains why an already-abnormal starting state directly increases the odds of hitting a genuine failure partway through the procedure.