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Coinbase Incident Post Mortem: June 25–26, 2019

blog.coinbase.com

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Re: Coinbase Incident Post Mortem: June 25–26, 2019

#11

Post by cle »

Lots of architectural and cultural problems IMO. Mixing different kinds of queries on the same cluster, no auto scaling on neither cluster nor web server, they seem to be okay with customer-impacting maintenance events (seriously?!), and their "fix" for an event caused by cache misses is to add more caching, which will make their system even harder to understand and predict, increasing the likelihood of more severe and byzantine failures.

It's often an unpopular opinion around here, but this is why I prefer simple hosted databases with limited query flexibility for high volume and high availability services (Firestore, DynamoDB, etc.). It's harder to be surprised by expensive queries, and you won't have to fiddle with failovers, auto scaling, caching, etc. Design your system around their constraints and it will have predictable performance and can more easily scale under unexpected load.

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#12

Post by rednixion »

viraptor wrote: post #8

> We have ensured that failovers for this cluster may only be initiated during rare, scheduled downtime, when there will be no impact on customers. I hope all their hardware crashes are also scheduled when there will be no impact... This seems a bit backwards - unless you constantly exercise the instantaneous failover, how do you know it works? Edit: Actually it's worse - if you don't test the instant failover under…

1: Sounds like they are saying that until the changes to remove the cluster out of the request path, failover cannot be trusted so the only immediate action that can be taken is to disable the automatic failover logic and prevent any live maintenance jobs needing to take it offline from running. Not unreasonable depending on the timeline to implement the changes when comparing the risk of a cluster killing hardware failure (assuming that there is at least a one node tolerance) vs behavior inside of your buy/sell pipeline being "undetermined"; no failover is probably a great way to keep the sprint work priority at the appropriate level.

2. Loadtesting? Accurate end-to-end loadtests are painful to bootstrap from nothing and requires an environment that can be expensive, worth their weight in gold depending on how critical downtime is or if everything in your platform is pulling from the same resource pool(ie appliance based deployment).

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#14

Post by Klathmon »

redis_mlc wrote: post #10

> We take uptime very seriously, and we’re working hard to support the millions of customers that choose Coinbase to manage their cryptocurrency No you don't. - If you did, you'd hire a DBA team and they would be familiar with the various jobs in your environment. But first your founders would have to have respect for Operations, which will take a dozen more major outages. The other major Coinbase outages have also b…

>you wouldn't be doing major database (or other production) changes at 3 pm in the afternoon.

Coinbase isn't dedicated to one timezone. They fully support tons of countries and have customers all over the place.

Things like this have to happen at some point, and there are benefits to doing stuff like this during "work" hours (like having all of your staff online and available)

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#15

Post by latchkey »

mbell wrote: post #6
oconnor663 wrote: post #4

Earlier quoted context omitted.

Sounds like a maintenance error and an application design error that led to a flood of traffic. Doesn't sound MongoDB specific.

I don't think there is enough information to come to a conclusion here, but I doubt your proposed failure mode. Based on my experience with largish data in mongo, my guess would be that the database size was >> than ram and, due at least in part to mongo's design, when the master failed over the memory state of the new master didn't have the working set present in RAM. This lead to a huge inrush of disk IO resulting…

My experience with mongo is the same. Works great, in RAM. As soon as you hit disk, it falls over completely.

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#16

Post by kerkeslager »

Klathmon wrote: post #14
redis_mlc wrote: post #10

> We take uptime very seriously, and we’re working hard to support the millions of customers that choose Coinbase to manage their cryptocurrency No you don't. - If you did, you'd hire a DBA team and they would be familiar with the various jobs in your environment. But first your founders would have to have respect for Operations, which will take a dozen more major outages. The other major Coinbase outages have also b…

>you wouldn't be doing major database (or other production) changes at 3 pm in the afternoon. Coinbase isn't dedicated to one timezone. They fully support tons of countries and have customers all over the place. Things like this have to happen at some point, and there are benefits to doing stuff like this during "work" hours (like having all of your staff online and available)

> Things like this have to happen at some point, and there are benefits to doing stuff like this during "work" hours (like having all of your staff online and available)

That sounds like a benefit to Coinbase and not to any of their customers.

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#17

Post by keyle »

redis_mlc wrote: post #10

> We take uptime very seriously, and we’re working hard to support the millions of customers that choose Coinbase to manage their cryptocurrency No you don't. - If you did, you'd hire a DBA team and they would be familiar with the various jobs in your environment. But first your founders would have to have respect for Operations, which will take a dozen more major outages. The other major Coinbase outages have also b…

> You prioritize features over Operations, and as a result guinea-pig your users. Just like any other SF startup. So just admit that to your end-users.

Wow, I'm not from any "SF startup" but I find that side jab quite cunning.

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#18

Post by staticassertion »

> Before the incident began, a background job performed an aggregation for a large number of accounts, causing excessive reads into cache and cache evictions for the cluster’s storage engine cache.

I thought this was interesting. I think that caches can be so dangerous in an incident - suddenly operations that are almost always constant time are executing in a much different complexity, and worst is that this tends to happen when you get backups (since old, uncached data is suddenly pushing recent data out).

I think chaos engineering may be a good solution here, in lieu of better architectures - see what happens when you clear your cache every once in a while, how much your load changes, how your systems scale to deal with it.

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#19

Post by wbl »

kerkeslager wrote: post #16
Klathmon wrote: post #14

Earlier quoted context omitted.

>you wouldn't be doing major database (or other production) changes at 3 pm in the afternoon. Coinbase isn't dedicated to one timezone. They fully support tons of countries and have customers all over the place. Things like this have to happen at some point, and there are benefits to doing stuff like this during "work" hours (like having all of your staff online and available)

> Things like this have to happen at some point, and there are benefits to doing stuff like this during "work" hours (like having all of your staff online and available) That sounds like a benefit to Coinbase and not to any of their customers.

If it shortens MTTR it's worth it. It has to be 3 PM for someone.

Re: Coinbase Incident Post Mortem: June 25–26, 2019

#20

Post by qes »

wbl wrote: post #19
kerkeslager wrote: post #16

Earlier quoted context omitted.

> Things like this have to happen at some point, and there are benefits to doing stuff like this during "work" hours (like having all of your staff online and available) That sounds like a benefit to Coinbase and not to any of their customers.

If it shortens MTTR it's worth it. It has to be 3 PM for someone.

Their users are far from evenly distributed across timezones.
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