[Cook] parallel confusion

[Peter Miller]

On Fri, Jun 20, 2003 at 11:07:54PM -0500, Jerry Pendergraft wrote:
> You should try to keep each recipe to a single command. Because multiple
> commands will definately run in different threads, even on different
> machines.

No, all the commands of a recipe body are executed in the same cook
thread (the thread-id will be constant and unique for the duration of
the recipe body execution).

But, yes, each command will be executed as a separate Unix process. 
And, yes, every command which needs a shell to run it (because it has
meta-characters to be interpreted) will get another separate Unix
process for each shell instance.

As a result, yes, each command could be executed on a different machine
if you are using the host-binding feature with more than one host named
(or Jerry's clever load balancing).

If you have a recipe body with more than one command in it, you could
(a) quote all but the last semicolon; or
(b) whack it all into a shell script, and have the recipe invoke the
shell scrip.
Either way, all the commands will be one command from Cook's
perspective.

-- 
Regards
Peter Miller <millerp at canb.auug.org.au>
/\/\*        http://www.canb.auug.org.au/~millerp/

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