Backend Drivers¶

The Driver Class¶

class oslo_config.sources.ConfigurationSourceDriver¶

A backend driver option for oslo.config.

For each group name listed in config_source on the DEFAULT group, a ConfigurationSourceDriver is responsible for creating one new instance of a ConfigurationSource. The proper driver class to be used is selected based on the driver option inside each one of the groups listed in config_source and loaded through entry points managed by stevedore using the namespace oslo.config.driver:

[DEFAULT]
config_source = source1
config_source = source2
...

[source1]
driver = remote_file
...

[source2]
driver = castellan
...

Each specific driver knows all the available options to properly instatiate a ConfigurationSource using the values comming from the given group in the open_source_from_opt_group() method and is able to generate sample config through the list_options_for_discovery() method.

list_options_for_discovery()¶

Return the list of options available to configure a new source.

Drivers should advertise all supported options in this method for the purpose of sample generation by oslo-config-generator.

For an example on how to implement this method you can check the remote_file driver at oslo_config.sources._uri.URIConfigurationSourceDriver.

Returns:	a list of supported options of a ConfigurationSource.

open_source_from_opt_group(conf, group_name)¶

Return an open configuration source.

Uses group_name to find the configuration settings for the new source and then open the configuration source and return it.

If a source cannot be open, raises an appropriate exception.

Parameters:	conf (ConfigOpts) – The active configuration option handler from which to seek configuration values. group_name (str) – The configuration option group name where the options for the source are stored.
Returns:	an instance of a subclass of ConfigurationSource

The Configuration Source Class¶

class oslo_config.sources.ConfigurationSource¶

A configuration source option for oslo.config.

A configuration source is able to fetch configuration values based on a (group, option) key from an external source that supports key-value mapping such as INI files, key-value stores, secret stores, and so on.

get(group_name, option_name, opt)¶

Return the value of the option from the group.

Parameters:	group_name (str) – Name of the group. option_name (str) – Name of the option. opt (Opt) – The option definition.
Returns:	A tuple (value, location) where value is the option value or oslo_config.sources._NoValue if the (group, option) is not present in the source, and location is a LocationInfo.

Remote File¶

The remote_file backend driver is the first driver implemented by oslo.config. It extends the previous limit of only accessing local files to a new scenario where it is possible to access configuration data over the network. The remote_file driver is based on the requests module and is capable of accessing remote files through HTTP or HTTPS.

To definition of a remote_file configuration data source can be as minimal as:

[DEFAULT]
config_source = external_config_group

[external_config_group]
driver = remote_file
uri = http://mydomain.com/path/to/config/data.conf

Or as complete as:

[DEFAULT]
config_source = external_config_group

[external_config_group]
driver = remote_file
uri = https://mydomain.com/path/to/config/data.conf
ca_path = /path/to/server/ca.pem
client_key = /path/to/my/key.pem
client_cert = /path/to/my/cert.pem

On the following sessions, you can find more information about this driver’s classes and its options.