[chef] Re: Re: Re: Re: race conditions during resource allocation

[Chris Walters < >]

Another thing to consider when designing our solution is that if the clients are running on the same interval, it's possible to get into a both-on-both-off periodic behavior (http://en.wikipedia.org/wiki/Deadlock#Livelock).

-chris

On Mon, Oct 19, 2009 at 11:28 AM, Adam Jacob < "> > wrote:

On Mon, Oct 19, 2009 at 9:32 AM, Nick Ohanian < "> > wrote:
> Thanks Adam.  After working with Chef a bit more, it occurred to me that
> Chef's "Convergence" model helps mitigate this problem.  If the nodes are
> checking in with the Chef server frequently, then on the next chef-run one
> of the nodes could realize that it's breaking a rule and act appropriately
> (thank you, splay).  As long as a small period of rule-violation doesn't
> blow up the entire deployment, the system should heal itself over time.

Right - if you can remove the need for absolute consistency and allow
things to be eventually consistent instead, you can work it out much
easier.

http://books.couchdb.org/relax/intro/eventual-consistency

Check out the section here on CAP theorem for the knobs you are tweaking. :)

Adam

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Opscode, Inc.
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