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Zookeeper, mail # user - Getting confused with the "recipe for lock"


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Zhao Boran 2013-01-11, 13:46
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Andrey Stepachev 2013-01-11, 14:48
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Hulunbier 2013-01-11, 16:10
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Jordan Zimmerman 2013-01-11, 20:20
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Hulunbier 2013-01-12, 10:30
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Ben Bangert 2013-01-12, 17:39
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Jordan Zimmerman 2013-01-13, 01:31
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Hulunbier 2013-01-13, 15:05
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Vitalii Tymchyshyn 2013-01-14, 10:37
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Hulunbier 2013-01-14, 15:06
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Vitalii Tymchyshyn 2013-01-14, 15:38
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Ted Dunning 2013-01-14, 16:05
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Hulunbier 2013-01-15, 02:28
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Hulunbier 2013-01-15, 01:52
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Jordan Zimmerman 2013-01-15, 02:23
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Hulunbier 2013-01-15, 03:45
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Benjamin Reed 2013-01-15, 05:27
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Hulunbier 2013-01-15, 06:32
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Ted Dunning 2013-01-17, 11:43
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Hulunbier 2013-01-18, 08:26
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Benjamin Reed 2013-01-17, 04:28
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Re: Getting confused with the "recipe for lock"
Hulunbier 2013-01-17, 09:05
Benjamin,

Greatly appreciate your thorough explanation, thanks a lot!

hunlunbier
On Thu, Jan 17, 2013 at 12:28 PM, Benjamin Reed <[EMAIL PROTECTED]> wrote:
>> Does this mean that session_expired event may be triggered all by
>> zk-client-library itself ?(by something like a built-in client-local
>> timer, without notification from zk server? )
>>
>> (I am digging into the source code, but in case of misunderstanding of
>> the code, I need your confirmation please)
>
> our general rule with zookeeper is to either give the correct answer
> or say "i don't know". connection loss is the zookeeper version of i
> don't know. you will only get the session expired event when the
> client gets confirmation from a server that the session is really
> gone. this means that even if a client is disconnected for days, you
> will not get the session expired until client connects to the server
> and the server tells it that the connection has expired.
>
>>
>>> HBase region servers went into gc for many minutes and then woke up still thinking they are the leader
>>
>> Could this happen if I just follow(correctly and without a
>> client-local timer or external fencing resources) the recipe for
>> distributed clock?
>
> this did happen with hbase. client-local timers don't help. there are
> multiple problems going on: if a process is the leader and the gc
> freezes time (or the process gets swapped out or the hypervisor
> suspends the vm) right before the instruction that can only be
> executed by a leader (send database update for example), when time
> unfreezes, the rest of the system knows the leader has changed,
> another thread in the process might be figuring it out, local timers
> might be ready to fire, but the "leader instruction" will execute
> since that is the next instruction for the CPU to execute.
>
> ben
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Vitalii Tymchyshyn 2013-01-27, 19:29
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Hulunbier 2013-01-13, 14:40