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I recently came across CockroachDB and thought it's capabilities interesting, almost too good to be true. I also have been looking at Citus Data which shards an
by jgalentine007 8y ago
I recently came across CockroachDB and thought it's capabilities interesting, almost too good to be true. I also have been looking at Citus Data which shards and distributes transactions, are you aware of any consistency shortcomings with it?
- cube2222 8y agoCockroachDB's performance is dependent on time synchronization. If a node detects it's too far behind, it will commit suicide. However, before it detects it, there is a possibility of stale reads. https://www.cockroachlabs.com/docs/stable/recommended-production-settings.html#clock-synchronization https://www.cockroachlabs.com/docs/stable/recommended-produc...
- jgalentine007 8y agoThanks for pointing that out - I have yet to rtfm and dive deep. I wonder how frequently time sync problems occur in virtual environments after ntp syncing - I've seen pretty erratic behavior on virtual active directory domain controllers even after syncing with hyper-v and vmware.
- brazzledazzle 8y agoIt’s been a long time since I messed with domain controllers but I believe Microsoft used to have explicit guides for handling time on virtual DCs. At that time we kept around a a couple hardware DCs to be safe but I do remember having the VMware agent correct the time could result in some bad results. I think it was because it immediately fixed the time and didn’t slowly correct the drift but it’s been a long time so my memory could be off.
- amaccuish 8y agoTime shouldn't be a massive issue for AD no? It's a vector clock, not a UTC clock. The UTC clock is only used to solve conflicts no?
- e12e 8y agoWhy do you say that? I thought kerberos depended on timestamps +/- drift? https://tools.ietf.org/html/rfc4120#section-5.2.3 https://tools.ietf.org/html/rfc4120#section-5.2.3 Or do you mean some other part of AD?
- amaccuish 8y agoIt defaults to 5 minutes. I perhaps wrongly assumed the issue was within 5 minutes.
- gurjeet 8y agoHere’s their blog post on how they manage to live without atomic clocks. I’ve found at least one assumption of thiers that i don’t agree with, but notwithstanding that, it’s a good read. https://www.cockroachlabs.com/blog/living-without-atomic-clocks https://www.cockroachlabs.com/blog/living-without-atomic-clo...
- atombender 8y agoMy experience from test workloads on Cockroach is that single transaction performance is very bad compared to something like Postgres -- with 2.0 I was seeing easily 10x worse performance than Postgres with a three-node test cluster on Google Cloud. My impression is that it's worse for apps that have lots of small CRUD transactions on low numbers of rows, as is typical with web/mobile UIs. Aggregate cluster performance seemed very good, though; i.e., adding a bunch more concurrent transactions did not slow down the other transactions noticeably.