4 ms·

or Spanner-like guarantees which I heard might be possible with CockroachDB. I'm not really sure how the two compare, and whether or not there is anything out t

or Spanner-like guarantees which I heard might be possible with CockroachDB. I'm not really sure how the two compare, and whether or not there is anything out there with similar strong consistency guarantees.

Royalaid 9y ago
Just an important point the guarantees cockroach provides and Google cloud spanner provide are slightly different. Cockroach provides serializability while Spanner provides linearizability.
tyingq 9y ago
There's a pretty good blog post from CockroachDB that explains the tradeoffs for not having the same level of time synchronization as spanner. https://www.cockroachlabs.com/blog/living-without-atomic-clocks/ https://www.cockroachlabs.com/blog/living-without-atomic-clo... CockroachDB is, though, only in it's first "real" 1.0 release. You see the sort of bugs you would expect to see in their repo. That is, basically, it's not really suitable for anything important yet. They do seem to be making a lot of progress though.
- idibidiart 9y ago
  Right. There is no GPS sync'd atomic clock in Cockroach so I imagine lock requests for a distributed object must use some consensus protocol, and that's overhead. Am I off by a lot?
  - tyingq 9y ago
    "Spanner always waits on writes for a short interval, whereas CockroachDB sometimes waits on reads for a longer interval." Where interval is clock drift.
  - irfansharif 9y ago
    We use Raft underneath the hood to maintain consistency across the replicas. re: 'There is no GPS sync'd atomic clock in Cockroach', Cockroach actually has a command line flag (--linearizable) which makes it behave like Spanner: wait for the max clock offset before returning a successful commit[1]. This isn’t practical if you’re using NTP synchronization, but if you have atomic clocks at your disposal.. [1]: https://www.cockroachlabs.com/blog/living-without-atomic-clocks/ https://www.cockroachlabs.com/blog/living-without-atomic-clo...

Royalaid 9y ago

Just an important point the guarantees cockroach provides and Google cloud spanner provide are slightly different. Cockroach provides serializability while Spanner provides linearizability.

tyingq 9y ago

There's a pretty good blog post from CockroachDB that explains the tradeoffs for not having the same level of time synchronization as spanner. https://www.cockroachlabs.com/blog/living-without-atomic-clocks/ https://www.cockroachlabs.com/blog/living-without-atomic-clo... CockroachDB is, though, only in it's first "real" 1.0 release. You see the sort of bugs you would expect to see in their repo. That is, basically, it's not really suitable for anything important yet. They do seem to be making a lot of progress though.

idibidiart 9y ago
Right. There is no GPS sync'd atomic clock in Cockroach so I imagine lock requests for a distributed object must use some consensus protocol, and that's overhead. Am I off by a lot?
- tyingq 9y ago
  "Spanner always waits on writes for a short interval, whereas CockroachDB sometimes waits on reads for a longer interval." Where interval is clock drift.
- irfansharif 9y ago
  We use Raft underneath the hood to maintain consistency across the replicas. re: 'There is no GPS sync'd atomic clock in Cockroach', Cockroach actually has a command line flag (--linearizable) which makes it behave like Spanner: wait for the max clock offset before returning a successful commit[1]. This isn’t practical if you’re using NTP synchronization, but if you have atomic clocks at your disposal.. [1]: https://www.cockroachlabs.com/blog/living-without-atomic-clocks/ https://www.cockroachlabs.com/blog/living-without-atomic-clo...