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Re: actionsequence suggestion


From: Tim Nelson
Subject: Re: actionsequence suggestion
Date: Mon, 10 Jan 2005 17:14:47 +1100 (EST)

On Thu, 6 Jan 2005 address@hidden wrote:

Something like this could be done in the future, but I would not do it with
classes. I would have priority attributes.  priority=X

Thanks for the suggestion
I shall have this in mind for cfengine 3

Hmm. The rc.x priorities system has recently been slammed because it is the way it is, instead of using dependencies (which would allow parallel execution, and greatly reduce startup time for Linux boxes). Additionally, a colleague sent me the following this morning
-------------------------------------
http://www.gotw.ca/publications/concurrency-ddj.htm

Executive Summary:
CPUs are no longer progressing n raw clock speed, and the future is in multicore and multithreaded processors. BUT this means that developers will be required to start thinking seriously about programming for these concurrent systems.
-------------------------------------

When I have problems like this, it's usually because I'm attempting to make things happen in a certain sequence. I know that cfengine is designed to work non-sequentially, but this is a problem for actions that need to happen in a sequence.

So, in my mind, we're trying to come up with a solution that works within the following constraints:
1.      Does not encourage sequential thinking (as this is not cfenginely)
2.      Allows sequential sequences where necessary
3.      Uses something more user-friendly than the current actionsequence
        solutions to these problems.

        I personally would like to add the following constraint:
4.      Is more elegant than the suggested priority system (which to my
        mind has the elegance of the old BASIC/ForTran line numbers).

        My suggestion would be to add *two* attributes:

        deptag=foo

....

        dependson=foo

These would be on two separate actions. In fact, this type of system could entirely replace the actionsequence, and would greatly enhance parallelisation abilities. Cfengine would merely need to resolve the dependency tree, and then it would know how to divide tasks between "thread", or whatever it is that we want to do.

        Hmm.  Definately not until cfengine 3, anyway :).

        :)

--
Tim Nelson
Server Administrator
WebAlive Technologies Global
Level 1 Innovation Building, Digital Harbour
1010 LaTrobe Street
Docklands, Melbourne, Vic, 3008
Phone: +61 3 9934 0812
Fax: +61 3 9934 0899
E-mail: address@hidden
http://www.webalive.biz/




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