How Complex Systems Fail (1998)
how.complexsystems.fail
how.complexsystems.fail
The most commonly cited subtext or thrust of it is that "root cause analysis", at least on complex systems, is a fools errand. Something goes wrong, say, in a distributed lock system, and your whole deployment system enters a metastable failure state. Naturally, the "root cause" seems like lock system resiliency. But definitionally a metastable failure is one that persists after the inciting condition is resolved. Now you have two "root causes", the lock failure and the metastability of the deployment system fault. Keep looking and you'll find more.
But to me the biggest brick to the forehead in this piece is further observation that random things are failing all the time in any complex system. "Complex systems run in degraded mode". Resilient components are good, but it's the resiliency of the overall process that orchestrates the whole system that determines whether things are going to blow up.
All practitioner actions are gambles. I should have that inked somewhere.
If you want a bit of cheese to go with that wine, this article pairs nicely with The Grug-Brained Developer: https://grugbrain.dev/
It's only an issue when people take that phrase very literally. People have common sense to understand that things have multiple causes and a chain of events. NASA has "Root Cause Analysis" (singular) all over various official documentation and it doesn't stop them from understanding that the failed O-rings were not the single root cause of the Challenger explosion. Another cause was management normalizing the deviations of previous unsafe datapoints of prior launches which let them greenlight the launch in freezing temperatures. Another cause was the unrealistic flight schedules which can subconsciously pressure management into normalizing dangerous deviations. It wasn't The Rogers Commission that found the multiple causes; it was NASA engineers and management themselves explaining the multiple causes as they were interviewed by the Rogers Commission members.
For whatever reason, alternative jargon such as "Root Causes Analysis" (plural) or "Proximate and Distal Causes Analysis" isn't as widely used.
In the case of Challenger, I think it's pretty clear this was the "root cause":
> According to testimony by Kilminster and Boisjoly, Mason finally turned to Bob Lund and said, "Take off your engineering hat and put on your management hat." Joe Kilminster wrote out the new recommendation and went back on line with the teleconference.
> The new recommendation stated that the cold was still a safety concern, but their people had found that the original data was indeed inconclusive and their "engineering assessment" was that launch was recommended, even though the engineers had no part in writing the new recommendation and refused to sign it.
-- https://onlineethics.virginia.edu/cases/engineering-ethics-c...
If you want to take the "system" view here, as is often the case, it is the organizational power structure and incentives therein that comprise the dangerous system. You had engineering experts easily predicting the disaster, but they had no decision making power. That was the problem. But if you set up an organization like that, where the egos of "get it done" managers are allowed to gamble with other people's lives to win their own accolades, the system is doomed from the start.
* the number five isn’t magical here. You don’t have to stop at five, and you often shouldn’t.
There's a "system" aspect (outside of power structures and incentives) which is that prob/stats knowledge among almost all engineering disciplines (industrial engineering waves from the sidelines) is exceedingly poor and often viewed as "soft" and "less important" than calculus, linear algebra, etc. And so practitioners are ill-equipped at spotting things like that ("wait, is this the right denominator? what about frequency of incident?").
This very much resembles Admiral Cloudberg's write-up of the National Airport collision:
"No human being can look at a complex system and predict with any degree of accuracy how exactly it will fail. But with sufficient data, prediction becomes possible because of something known in the occupational safety field as Heinrich’s Law, which states that there are approximately 300 “near misses” for every serious accident; or as the latest version of the law puts it, each fatal accident is accompanied by about 3,000 near misses and about 30,000 “at-risk behaviors.”[39] Statistically, hundreds or thousands of at-risk behaviors and near misses are likely to occur prior to the first fatal accident, providing an opportunity to identify the risk before lives are lost."
https://admiralcloudberg.medium.com/reaping-the-whirlwind-in...
> All of the interesting systems (e.g. transportation, healthcare, power generation) are inherently and unavoidably hazardous by THE own nature.
(Emphasis mine)
I am not sure if that's a typo, or some writing convention that my uneducated mind can't grok.
https://en.wikipedia.org/wiki/Normal_Accidents
https://en.wikipedia.org/wiki/Meltdown_(Clearfield_and_Tilcs...
I disagree with this point. From what I have seen and experienced, there are so many SPOFs in the real-world complex systems that do not have adequate defense or even any defense at all. The only reason catastrophe didn't occur (often) is only because the natural failure rate is extremely low. Like the probability of air traffic controller making a critical mistake is very low, maybe once every few years, but when it happens, the SPOF will almost certainly cause a disaster, and the system (ie. the way air traffic is controlled today) has been around for decades and is so outdated but the cost of changing the entire process around the world is simply way too high so we just take this as "normal".
Safety I Learn from Errors, Safety defined by absence,Reactive approach, Understanding what goes wrong, Accident causation models, Avoidance of errors, Reducing losses
Safety II Learn from successes, Safety defined by presence, Proactive approach, Understanding what goes right, Repeat what goes right, Enforce successful behaviours, Create new processes based on successful behaviour
If anything, think long and hard about this: "Post-accident attribution to a ‘root cause’ is fundamentally wrong." It's a true statement. If you truly understand this sentence, you have mastered Safety II to the level that a light bulb will come on, and you won't be able to un-see it. This light bulb is a curse, a beautiful curse.
[1] https://safety4sea.com/cm-safety-i-vs-safety-ii-an-overview [2] https://www.msoos.org/largefiles/safety2.pdf