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From Satish Mittal <satish.mit...@gmail.com>
Subject synchronize installation across services at cluster level
Date Thu, 08 Aug 2013 06:54:14 GMT
Hi,

Let's say I have my cluster topology like:

whirr.instance-templates=1 service-A+service-B, 1 service-A+service-B

In my scenario, service-B should first wait for all service-A instances to
come up, so that I can create some tables and populate data on only one
instance of service-B.

For this purpose, I first need a callback after service-A has been
installed on all cluster instances, so that I can perform certain one-time
activities at that point. Do we already have such a callback in whirr
interfaces? I checked out ClusterActionHandler interface, but my
understanding is that it applies at role level on each instance. So
bootstrap/configure/start/stop get called for each instance of service-A. I
couldn't find a callback when all service-A instances are installed.

Additionally, is it possible to synchronize installation/starting of
service-B only after all instances of service-A are installed/started?
Basically, I am looking for a DAG kind of dependency mechanism to be
configured across services.

Thanks,
Satish

-- 
"The happiest of people donĀ“t necessarily have the best of everything, they
just make the most of everything that comes along their way."

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