So, should we change CURATOR-246 into a larger issue for supporting a true SESSION_LOST state as well as pluggable error handling? If so, it would be nice to have this for 3.0
-Jordan On August 20, 2015 at 11:19:21 AM, Scott Blum ([email protected]) wrote: Assuming that clocks are usually not too out of step, Curator should be able to infer when the server would have terminated the existing session based on the clock. A little bit of thought would need to be put into resolving the race condition when you reconnect right as you were about to time out, in order to present a unified view of the state change, but that doesn't seem infeasible. This seems like exactly the kind of problem Curator should be solving. On Thu, Aug 20, 2015 at 11:21 AM, Jordan Zimmerman <[email protected]> wrote: Yeah, in hindsight LOST isn’t useful which is why all the recipes refer to SUSPENDED. Having a session-expired state is complicated in Curator as Curator sometimes re-creates the connection without a ZK generated event. So, the SESSION lost would have to be inferred. -Jordan On August 20, 2015 at 10:13:19 AM, Scott Blum ([email protected]) wrote: Ahh... that is confusing, and seems dubiously useful. I think 99% of the time I'd rather get an event that represents that the session is definitely lost. On Thu, Aug 20, 2015 at 10:53 AM, Jordan Zimmerman <[email protected]> wrote: Maybe I'm confused, but I thought that's what ConnectionState SUSPENDED vs. LOST was all about? It’s a big source of confusion with Curator. LOST does _not_ mean the session was lost. It means Curator has given up after retries, etc. Because Curator re-creates ZK handles internally the notion of a “session” is more complicated than using raw ZooKeeper. -Jordan On August 20, 2015 at 9:50:56 AM, Scott Blum ([email protected]) wrote: Maybe I'm confused, but I thought that's what ConnectionState SUSPENDED vs. LOST was all about? Maybe the recipes just need to be tweaked a bit? I always assumed emphemeral nodes would be gone on LOST but not gone if you get a SUSPENDED followed by RECONNECTED. The one question I've always wondered is what happens to Watchers on SUSPENDED, do they all need to be re-applied, or will they still fire later as long as you don't get LOST? On Thu, Aug 20, 2015 at 10:41 AM, Jordan Zimmerman < [email protected]> wrote: > I wonder if we can add error handling policies to Curator. Currently, the > policy of all recipes is hard-coded to treat SUSPENDED as a type of lost > session. We could change this to be injected like the retry policy. To > solve this particular issue we’d also need to introduce a SESSION_LOST > state of some type. This is complicated as Curator re-creates connections > internally. > > Thoughts? > > -Jordan > > > > On August 20, 2015 at 2:10:52 AM, Dong Lei ([email protected]) wrote: > > Hi curator-devs: > > We use Spark in standalone mode in which Spark leverage curator to manage > ZK connections and elect leader. Our Zookeeper may be not very stable and > we get "session suspended and reconnected" sometimes. The problem is that > this kind of disassociated and reconnected triggers leader election quite > often. And Spark's reaction to leadership switching can be very costly. > > So I'm thinking about whether it's possible to tolerate such failure cases > if we can reconnect soon and the session is actually kept after the > reconnection? > Or does such a requirement makes sense to you? > > Any advice will be appreciated. > > > Thanks > Dong Lei > >
