[openstack-dev] Unified Guest Agent proposal

Steven Dake sdake at redhat.com
Sat Dec 14 17:00:53 UTC 2013

On 12/13/2013 01:13 PM, Clint Byrum wrote:
> Excerpts from Dmitry Mescheryakov's message of 2013-12-13 12:01:01 -0800:
>> Still, what about one more server process users will have to run? I see
>> unified agent as library which can be easily adopted by both exiting and
>> new OpenStack projects. The need to configure and maintain Salt server
>> process is big burden for end users. That idea will definitely scare off
>> adoption of the agent. And at the same time what are the gains of having
>> that server process? I don't really see to many of them.

I tend to agree, I don't see a big advantage to using something like 
salt, when the current extremely simplistic cfn-init + friends do the job.

What specific problem does salt solve?  I guess I missed that context in 
this long thread.

> The Salt devs already mentioned that we can more or less just import
> salt's master code and run that inside the existing server processes. So
> Savanna would have a salt master capability, and so would Heat Engine.
I really don't think we want to introduce a salt executive into the heat 
engine process address space, even if it is as simple as an import 
operation.  Sounds like a debugging nightmare!

> If it isn't eventlet friendly we can just fork it off and run it as its
> own child. Still better than inventing our own.
fork/exec is not the answer to scalability and availability I was 
looking for :)  So, given that we need scale+availability, we are back 
to managing a daemon outside the address space, which essentially 
introduces another daemon to be scaled and ha-ified (and documented, 
etc, see long zookeeper thread for my arguments against new server 
processes...).  import is not the answer, or atleast it won't be for heat...

Salt just seems like more trouble then it is worth, but I don't totally 
understand the rationale for introducing it as a dependency in this 
case, and I generally think dependencies are evil :)

What are we inventing our own again of?  cfn-init & friends already 
exist, are dead simple, and have no need of anything beyond a metadata 
server.  I would like to see that level of simplicity in any unified agent.


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