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From Chiradeep Vittal <>
Subject Re: AutoScale feature....
Date Tue, 03 Jul 2012 17:49:47 GMT

On 7/2/12 11:43 PM, "Youcef Laribi" <> wrote:

>In a nutshell, the framework is as follows:
>1.       VM Counters that specify the monitored aspects of the VMs (some
>of these counters are monitored through SNMP agents running inside the VM
>- hence they are of the SNMP type)

This is specific to the implementation. There are several ways to monitor
performance. SNMP is just one. Hence it should not be part of the API. It
can be a generic key-value pair (for an example, look at the

>2.       AutoScale Policy to express the low and high watermark
>thresholds on counters to trigger a scaling up/down action.

This is generic

>3.       VM Profile that contains the details needed to auto-instantiates
>VMs and captures anything VM-specific (template, service offering,
>network, VM's SNMP agent port and community, etc.)

Template, service offering and network are generic, SNMP is not.

>4.       AutoScale Group which represents the dynamic list of autoscale
>VMs (min/max members in this group), and associates with them an
>autoscale policy  and a VM profile. Once defined, the AutoScale Group is
>assigned to the LB Rule (just like assigning manually one VM/instance to
>an LB Rule).

This is generic
>This is a generic framework.
>The implementation relies on the LoadBalancer Resource being able to
>support this new config item in an LB Rule. Any LB offering in CloudStack
>can support this new additional config and is free in the way it
>implements it. CloudStack will only allow configuring this feature on an
>LB Rule when the network LB offering supports it. The NetScaler offering
>will support this new feature, and we are extending the existing
>NetScaler Resource layer to implement it.

It is not necessary for an LB to implement the auto scaling. Any other
component can do the same. For example, a component can monitor via
hypervisor stats, or volume IO stats. So in this sense it is not generic.



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