Distributed configuration

Three modules:

1. the daemon, has a configuration file. It reads the configuration on startup or when explicitly requested to re-read the configuration.

   It is not an option for the daemon to request the configuration value via SQL for instance, which would generate network requests all the time, the daemon has a local cache. Either a zodb cache, or a memcache, or there is a protocol to notify the daemon to reload the configuration

2. the persistence, it could be a Couchdb, a Zodb, a Postgresql with a Storm. It could be anything, but it needs to be sexy. It stores the configuration so that when the server reboots, it does not forget its configuration.

3. the interface either web or command line, it needs to be deported so that one interface can communicate with multiple backends.

The interface is a Grok site or a command line, writing to a zeo zodb, the daemon can read the configuration in the zeo zodb. Or the interface can be a Grok site using storm around Sqlite.

Let's roll: the points of configuration for the daemon is log verbosity which is a boolean, ip and port:

{ "verbosity"  : "false",
  "ip_address" : "127.0.0.1",
  "port"       : "8080" }

On the platform, the daemon has the identifier basil, so the in the store, the three parameters are located under the basil node, under the root node.

Let's first build

• a command line which sets up the zodb, the default values. It is called config-setup.py, and expects a defaults.py with the interface named after the daemon identifier, and detailing the default values,

def - a command line which can talk to a zeo zodb, and get, set the

options. It is named config.py, and has the --id set, for instance, to basil then takes a json configuration file,

Setting up the configuration repository

1. it declares the hard coded Data.fs file storage in the current directory,
2. looping in the interfaces directory, it loads the class based on the zope.interfaces. An object conforming to the interface, and whose values are the default value is instantiated and stored in the ZODB.
   1. list the interfaces of a package,