This was a focus in our after-action review. The nodes responded as healthy to active checks, while silently dropping updates on their replication lag, together this created the impression of a healthy node. The missing bit was verifying the absence of lag updates. (Which we have now.)
You might want to clarify this in the post. To me it reads like you knowingly had degraded infra for days leading up to an incident which might have been preventable had you recovered this instances.
I am a curious and very amateur person, but do you think that if "100%" uptime were your goal, this:
"[Three months prior to the incident] We upgraded our databases to a new minor version that introduced a subtle, undetected fault in the database’s failover system."
could have been prevented if you had stopped upgrading minor versions, i.e. froze on one specific version and not even applied security fixes, instead relying on containing it as a "known" vulnerable database?
The reason I ask is that I heard of ATM's still running windows XP or stuff like that. but if it's not networked could it be that that actually has a bigger uptime than anything you can do on windows 7 or 10?
what I mean is even though it is hilariously out of date to be using windows xp, still, by any measure it's had a billion device-days to expose its failure modes.
when you upgrade to the latest minor version of databases, don't you sacrifice the known bad for an unknown good?
> could have been prevented if you had stopped upgrading minor versions, i.e. froze on one specific version and not even applied security fixes, instead relying on containing it as a "known" vulnerable database?
This is a valid question.
As a database and security expert, I carefully weigh database changes. However, developers and security zealots typically charge ahead "because compliance."
Same user (sorry I guess I didn't enter my password carefully as I can't log in.)
Well I mean they're not exactly on the Internet with an IP address and no firewall, are they? (Or they would have been compromised already.)
Whatever it is, it must be separated off as an "insecure enclave".
So that's why I'm wondering about this technique. You don't just miss out on security updates, you miss performance and architecture improvements, too, if you stop upgrading.
But can that be the path toward 100% uptime? Known bad and out of date configurations, carefully maintained in a brittle known state?
No, it's a fair question. The word "enclave" has a general meaning in English as a state surrounded entirely by another, or metaphorically a zone with some degree of isolation from its surroundings.
So the legit question is, can insecure systems (e.g. ancient mainframes) be wrapped by a security layer (WAF, etc.) to get better uptime than patching an exposed system?
Stripe splits data by kind into different database clusters and by quantity into different shards. Each cluster has many shards, and each shard has multiple redundant nodes.
having a few nodes down is perfectly acceptable. I guess they would have had an alert if the number of down nodes exceeded some threshold.
this case that doesn't sound like it was the issue, it was the lack of promotion of new master due to the bug in the system in terms of shard promotion.
Right, but they didn't recover speedily. To have the cluster in such a state for so long sounds like poor monitoring to me because this can knowingly interfere with an election later.
This was a focus in our after-action review. The nodes responded as healthy to active checks, while silently dropping updates on their replication lag, together this created the impression of a healthy node. The missing bit was verifying the absence of lag updates. (Which we have now.)