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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: leader election, scheduled tasks, losing leadership
Date Sun, 09 Dec 2012 05:00:44 GMT
The leader latch lock is the equivalent of task in progress. I assume the task is running in
the same VM as the leader lock. The only reason the VM would lose leadership is if it crashes
in which case the process would die anyway.

-JZ

On Dec 8, 2012, at 8:56 PM, Eric Pederson <ericacm@gmail.com> wrote:

> If I recall correctly it was Henry Robinson that gave me the advice to have
> a "task in progress" check.
> 
> 
> -- Eric
> 
> 
> 
> On Sat, Dec 8, 2012 at 11:54 PM, Eric Pederson <ericacm@gmail.com> wrote:
> 
>> I am using Curator LeaderLatch :)
>> 
>> 
>> -- Eric
>> 
>> 
>> 
>> 
>> On Sat, Dec 8, 2012 at 11:52 PM, Jordan Zimmerman <
>> jordan@jordanzimmerman.com> wrote:
>> 
>>> You might check your leader implementation. Writing a correct leader
>>> recipe is actually quite challenging due to edge cases. Have a look at
>>> Curator (disclosure: I wrote it) for an example.
>>> 
>>> -JZ
>>> 
>>> On Dec 8, 2012, at 8:49 PM, Eric Pederson <ericacm@gmail.com> wrote:
>>> 
>>>> Actually I had the same thought and didn't consider having to do this
>>> until
>>>> I talked about my project at a Zookeeper User Group a month or so ago
>>> and I
>>>> was given this advice.
>>>> 
>>>> I know that I do see leadership being lost/transferred when one of the
>>> ZK
>>>> servers is restarted (not the whole ensemble).   And it seems like I've
>>>> seen it happen even when the ensemble stays totally stable (though I am
>>> not
>>>> 100% sure as it's been a while since I have worked on this particular
>>>> application).
>>>> 
>>>> 
>>>> 
>>>> -- Eric
>>>> 
>>>> 
>>>> 
>>>> On Sat, Dec 8, 2012 at 11:25 PM, Jordan Zimmerman <
>>>> jordan@jordanzimmerman.com> wrote:
>>>> 
>>>>> Why would it lose leadership? The only reason I can think of is if the
>>> ZK
>>>>> cluster goes down. In normal use, the ZK cluster won't go down (I
>>> assume
>>>>> you're running 3 or 5 instances).
>>>>> 
>>>>> -JZ
>>>>> 
>>>>> On Dec 8, 2012, at 8:17 PM, Eric Pederson <ericacm@gmail.com> wrote:
>>>>> 
>>>>>> During the time the task is running a cluster member could lose its
>>>>>> leadership.
>>>>> 
>>>>> 
>>> 
>>> 
>> 


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