Thanks everyone for the replies. Seems like there is no easy way to handle this. It's very surprising that no one seems to have solved such a common use case.
-- Drew On Jan 6, 2012, at 2:11 PM, Bryce Allen wrote: > That's a good question, and I'm not sure - I'm fairly new to both ZK > and Cassandra. I found this wiki page: > http://wiki.apache.org/hadoop/ZooKeeper/FailureScenarios > and I think the lock recipe still works, even if a stale read happens. > Assuming that wiki page is correct. > > There is still subtlety to locking with ZK though, see (Locks based > on ephemeral nodes) from the zk mailing list in October: > http://mail-archives.apache.org/mod_mbox/zookeeper-user/201110.mbox/thread?0 > > -Bryce > > On Fri, 6 Jan 2012 13:36:52 -0800 > Drew Kutcharian <d...@venarc.com> wrote: >> Bryce, >> >> I'm not sure about ZooKeeper, but I know if you have a partition >> between HazelCast nodes, than the nodes can acquire the same lock >> independently in each divided partition. How does ZooKeeper handle >> this situation? >> >> -- Drew >> >> >> On Jan 6, 2012, at 12:48 PM, Bryce Allen wrote: >> >>> On Fri, 6 Jan 2012 10:03:38 -0800 >>> Drew Kutcharian <d...@venarc.com> wrote: >>>> I know that this can be done using a lock manager such as ZooKeeper >>>> or HazelCast, but the issue with using either of them is that if >>>> ZooKeeper or HazelCast is down, then you can't be sure about the >>>> reliability of the lock. So this potentially, in the very rare >>>> instance where the lock manager is down and two users are >>>> registering with the same email, can cause major issues. >>> >>> For most applications, if the lock managers is down, you don't >>> acquire the lock, so you don't enter the critical section. Rather >>> than allowing inconsistency, you become unavailable (at least to >>> writes that require a lock). >>> >>> -Bryce >>
