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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: ZK Client won't time out when quorum irrevocably goes away
Date Fri, 04 Feb 2011 00:08:39 GMT

Is it really impossible for the client to say that soooo much time has
passed in disconnected state that the session MUST have expired by now?

I have heard this assertion before and it always irked me a bit, but Ryan's
scenario is a great thought experiment (well, though experiment for US, not
for him).  Why can't those clients decide the session is expired after 3
days when the timeout is 3 minutes?

On Thu, Feb 3, 2011 at 4:01 PM, Patrick Hunt <phunt@apache.org> wrote:

> On Thu, Feb 3, 2011 at 2:57 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:
> > The result was the client never realized that it's session was
> > actually timed out, and the HBase processes continued to run. Kill -9
> > and a restart fixed it.
> Hi Ryan,
> there are two issues at play here, session timeout and session
> expiration. Correct me if I'm wrong but I think you meant to say "the
> client never realized that it's session was actually _expired_". Which
> is correct behavior. Clients can only determine if a session is
> expired once they reconnect to the cluster. Session timeout on the
> other hand happens when the server heartbeat is not received by the
> client w/in the session timeout period. Clients who are disconnected
> from the cluster will attempt to reconnect back to the cluster until
> they are successful. When a client is disconnected the client's
> watchers will be notified about the disconnect. (same for expiration).
> See questions 1 & 2 here in the faq, specifically "Example state
> transitions" in question 2:
> https://cwiki.apache.org/confluence/display/ZOOKEEPER/FAQ
> Your clients were stuck btw steps 4 and 5 (which they will never reach
> in your scenario).
> Does that help?
> Patrick

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