Re: [Ganglia-developers] Auto configuration ideas

[Carlo M. A. B. <ca...@sa...>]

On Tue, Aug 12, 2008 at 02:14:15PM +0100, Dan...@ba... wrote:
> > fair, and so for the sake of clarity let me explain again 
> > what are the specification constrains :
> > 
> > * must allow for nodes to specify where the configuration server is
> > * must allow for additional configurations to be included for modules
> > * must allow for configuration updates
> > * should allow for nodes to be notified when configuration changes
> >   require them to be reloaded
> > * should allow caching the configuration locally
> > * should fallback gracefully in case configuration server is 
> > not available
> > * should provide other applications (like gmetric) 
> > configuration services
> 
> Here is my proposal:
> - insert a dynamic_configuration step immediately after parsing the text
> files and before any of the cfg_t structures are examined

how would this work for module configurations which could in theory also
include their own "dynamic_configuration" sections?

are all "dynamic_configuration" sections assumed to be global? how would you
deal with multiple entries? how would you handle configuration caching? how
do you handle other consumers of the configuration like gmetric?

> - the dynamic_configuration() code loads a user specified module

to avoid confusion it will be better if those modules are not together with
the metric modules.  using "moduledir/conf/" instead of "moduledir/" should be
enough to do that.

> - the mechanism is purely optional and can be bypassed if the module
> fails
> 
> Something like this is added to gmond.conf:
> 
> dynamic_configuration {
>   module_path = "/tmp/mod_config_test.so"
>   param = "http://localhost/get_ganglia_opts.php?host=%s"
> }
> 
> The module can use methods like cfg_setstr() to override the values
> loaded from the configuration files.

still think that getting this into gmond is a stretch and even if the
implementation is done in gmond there is really no reason why this can't go
to a different configuration file.

> ===================================================================
> --- include/ganglia.h   (revision 1635)
> +++ include/ganglia.h   (working copy)
> @@ -2,11 +2,14 @@
>  #define GANGLIA_H 1
>  #include <rpc/rpc.h>
>  
> +#include <gm_mmn.h>
>  #include <gm_msg.h>
>  #ifndef GM_PROTOCOL_GUARD
>  #include <gm_protocol.h>
>  #endif
>  
> +#include <confuse.h>

this changes our ABI and adds a external dependency to libConfuse which
I am not sure is warranted/desirable.

> Index: gmond/gmond.c
> ===================================================================
> --- gmond/gmond.c       (revision 1635)
> +++ gmond/gmond.c       (working copy)
> @@ -199,17 +199,34 @@
>  mmodule *metric_modules = NULL;
>  extern int daemon_proc;     /* defined in error.c */
>  
> +void dynamic_configuration();
> +

can't be this forward declaration be avoided?

Carlo