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From Patrick Hunt <ph...@apache.org>
Subject Re: is there a good pattern for leases ?
Date Wed, 24 Feb 2010 20:15:42 GMT
Not sure if there is a jira on this but I have long been lobbying the 
team to add a new API/feature that allows clients to get a view of the 
"global clock". I think this would be a very useful (although admittedly 
potentially damaging) feature to add, esp around leases. If we think 
leases are something that we want to provide in future we may want to 
think about how we could more easily support this type of recipe.


Henry Robinson wrote:
> A cautionary note with this problem - who says when 2 minutes is up? Clocks
> will go forward at different rates and with different offsets. You cannot
> rely on two machines having the same perception of what 2 minutes means. In
> general, in distributed systems, it's a good design principle to minimise
> any dependence on a common notion of real time.
> That said the best way is to pick some machine, like Mahadev says, to retire
> old locks by polling every N seconds, where N is the slop you can afford.
> What problem are you actually trying to solve?
> cheers,
> Henry
> On 24 February 2010 03:40, Martin Waite <waite.134@googlemail.com> wrote:
>> Hi,
>> Is there a good model for implementing leases in Zookeeper ?
>> What I want to achieve is for a client to create a lock, and for that lock
>> to disappear two minutes later - regardless of whether the client is still
>> connected to zk.   Like ephemeral nodes - but with a time delay.
>> regards,
>> Martin

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