On 2014-16-05 18:29, Andy Parker wrote:
On Thu, May 15, 2014 at 10:24 PM, David Schmitt <da...@dasz.at
<mailto:da...@dasz.at>> wrote:
Hi,
On 16.05.2014 02:17, Alessandro Franceschi wrote:
On Thursday, May 15, 2014 9:55:05 PM UTC+2, John Bollinger wrote:
I am concerned about the impact. It is already somewhat
costly for
Puppet to evaluate data bindings for class parameters, and
adding
bindings for resource parameters (even just for resources
of defined
types) will magnify that. Note that the cost scales with the
aggregate number of defined parameters for all declared
resources,
independent whether any data are actually bound. In fact,
the cases
were no data are bound are the most costly, because hiera
must then
search the entire hierarchy.
Yes, these are valid and convincing points.
Anyway if we find data binding useful for classes and can bear the
performance overhead, I suppose we can do the same for defined
types.
I very much like the idea for data binding on all parameters, but
this statement is really not universally true. I've got catalogs
with only tens of classes but thousands of resources. That works out
to 100x more hiera calls. :-/
John makes a very good point about the performance cost. The impact of
putting data bindings on everything is made even worse by the fact that
it is an all or nothing price you have to pay, there isn't any way to
use it for just a subset of your catalog.
As a little number collection, would some of you mind doing a little
experiment and posting the numbers?
Run "puppet apply -e 'notice(hiera("somekey", 1), hiera("otherkey", 1))'
--profile --debug"
Make sure that it is using your real hiera config with your real data
files or else it won't be an accurate reflection of the cost. You'll get
output that should contain something like this:
Debug: PROFILE [apply] 2.2 Compile: Created settings scope: took 0.0103
seconds
Debug: hiera(): Hiera YAML backend starting
Debug: hiera(): Looking up somekey in YAML backend
Debug: hiera(): Looking for data source common
Debug: hiera(): Cannot find datafile /var/lib/hiera/common.yaml, skipping
Debug: PROFILE [apply] 2.3.1 Called hiera: took 0.0019 seconds
Debug: hiera(): Looking up otherkey in YAML backend
Debug: hiera(): Looking for data source common
Debug: hiera(): Cannot find datafile /var/lib/hiera/common.yaml, skipping
Debug: PROFILE [apply] 2.3.2 Called hiera: took 0.0002 seconds
I don't have hiera setup on this machine so it didn't do anything, but
you can see how much overhead *per-parameter* data bindings introduces.
So in a system with no hierarchy, and no data files (and in fact no
hiera config) it adds about 2 usec per parameter.
Note that this is per defined parameter per type since it obviously need
to process them all. Not per actually used parameter.
- henrik
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