Re: [Bigdata-developers] Why zookeeper?

[Fred O. <fko...@gm...>]

Bryan,

We have no plan to use hot spares. That is, we expect an HA system to
stay up and running long enough for an operator to diagnose a problem,
and either fix it or manually configure and start a cold spare if
necessary. I feel that automating this process when the actual faults
are not understood is too likely to cause harm than help.

Otherwise, why not have a set of HotSpare{Data,Metadata,...}Service
instances configured and running on the hot spare machines, ready to
become full participants when an HA quorum leader (or whatever
mechanism) identifies a need? When a new XXXService is needed, a
HotSpareXXXService is discovered and activated, registering a real
XXXService. (Credit to Sean.)

Fred


On Tue, Jul 20, 2010 at 5:16 PM, Bryan Thompson <br...@sy...> wrote:
> Fred,
>
> If you are not running the SMS, then you can simply start whatever services you want to start locally.  The SMS is not used for anything besides actually starting the various services.  Alternatively, a simpler SMS implementation could be used which read the list of services to start from a local configuration and ignored zookeeper.
>
> How would you propose to handle HA in that scenario?  There is still a problem with dynamic recruitment from the pool of hot spares.
>
> Thanks,
> Bryan