> [...] I am working with a database that has to have a lot of things configured -- one of them is how big the buffers should be, which is a function of how much RAM you have, which in turn depends on the kind of AWS instance my product runs on.
Which has nothing to do with the configuration format itself, it only needs
some knowledge when building config files. It can be achieved as easily with
a simple template (that doesn't understand the config it produces!), only
supplied with information local to the system the config is going to work
under. The easiest way is to build the config from a template on the system
it's going to run, but masterful Puppet with its facts database can do it on
the side of commanding server as well.
If the template system doesn't understand the semantics of the configuration file, templates just work because you are lucky. In the case of blending configuration changes with a user-supplied file, the user can supply a configuration file instead of a template.
If the system does understand the configuration file, then you can get the full value out of having a "fact database" that describes the system.
> If the template system doesn't understand the semantics of the configuration file, templates just work because you are lucky.
Or because I put appropriate constraints on data filling the template. Integer
fields are the easiest format to handle.
Generating configs with template systems is surprisingly strudy in real world
scenarios, where at least half-competent programmer provides templates for at
least half-competent sysadmin to fill.
> If the system does understand the configuration file, then you can get the full value out of having a "fact database" that describes the system.
The problem is that this "full value" is not that much bigger, but the effort
in understanding config file formats is quite large.
The work is large because parser generators are designed for systems programmers and not for application programmers. They haven't advanced much in terms of usability, thus parsing seems like a much harder problem than it really is.
Which has nothing to do with the configuration format itself, it only needs some knowledge when building config files. It can be achieved as easily with a simple template (that doesn't understand the config it produces!), only supplied with information local to the system the config is going to work under. The easiest way is to build the config from a template on the system it's going to run, but masterful Puppet with its facts database can do it on the side of commanding server as well.