Running a Service That Stays Up
The Gap Between Your Target and Perfection Is a Resource
Last timeA Number, Not a Feeling
Subtract the target from one and you get a budget: an amount of failure you are allowed to produce. Spending it deliberately is the whole method.
A target of 99.9 percent says something stronger than it appears to. It says
that one request in a thousand is permitted to fail, and that this is not an
accident but a plan. The remaining thousandth is a resource with an owner.
- the share of the window the target does not promise
- the length of the window, in minutes
Where the budget comes from
The same quantity can be counted in requests instead of minutes, and usually
should be for a service whose traffic is uneven. A thousandth of ten million
requests is ten thousand failures, and ten thousand failures concentrated into
one bad minute is a different experience from the same number spread evenly over
a month, even though both fit inside the budget.
What it is for
The budget exists to settle an argument that otherwise cannot be settled.
The lesson stops here
3 more paragraphs to go
You have read the opening. The rest of the argument, the problems that check whether it landed, and the lines worth keeping at the end all come with a plan.
The first lesson of every course in the library reads the whole way through, free, so you can see exactly what the rest of them are.
See the planThe contentsThis is the reading half
Starting the course gives you your own copy of it. Every idea on every page has problems standing under it, marked with a reason rather than a tick, and any sentence you do not believe can be opened and argued with. None of that can happen on a page nobody owns.
The contents