Config

Store configuration in ConfigNamespace objects and provide tools for reloading, and displaying help messages.

Configuration Reloading

Configuration reloading is supported using a ConfigFacade, which composes a ConfigurationWatcher and a ReloadCallbackChain. These classes provide a way of reloading configuration when the file is modified.

class staticconf.config.ConfigFacade(watcher: ConfigurationWatcher)

A facade around a ConfigurationWatcher and a ReloadCallbackChain. See ConfigFacade.load().

When a ConfigFacade is loaded it will clear the namespace of all configuration and load the file into the namespace. If this is not the behaviour you want, use a ConfigurationWatcher instead.

Usage:

import staticconf

watcher = staticconf.ConfigFacade.load(
    'config.yaml', # Filename or list of filenames to watch
    'my_namespace',
    staticconf.YamlConfiguration, # Callable which takes the filename
    min_interval=3 # Wait at least 3 seconds before checking modified time
)

watcher.add_callback('identifier', do_this_after_reload)
watcher.reload_if_changed()

classmethod load(filename: str, namespace: str, loader_func: LoadFunc, min_interval: float = 0, comparators: Optional[List[Type[IComparator]]] = None) → ConfigFacade

Create a new ConfigurationWatcher and load the initial configuration by calling loader_func.

Parameters:

• filename – a filename or list of filenames to monitor for changes

• namespace – the name of a namespace to use when loading configuration. All config data from filename will end up in a ConfigNamespace with this name

• loader_func – a function which accepts two arguments and uses loader functions from staticconf.loader to load configuration data into a namespace. The arguments are filename and namespace

• min_interval – minimum number of seconds to wait between calls to os.path.getmtime() to check if a file has been modified.

• comparators – a list of classes which support the IComparator interface which are used to determine if a config file has been modified. See ConfigurationWatcher::__init__.

Returns:

a ConfigFacade

reload_if_changed(force: bool = False) → None

See ConfigurationWatcher.reload_if_changed()

class staticconf.config.ConfigNamespace(name: str)

A container for related configuration values. Values are stored using flattened keys which map to values.

Values are added to this container using staticconf.loader. When a ConfigNamespace is created, it persists for the entire life of the process. Values will stay in the namespace until clear() is called to remove them.

To retrieve a namespace, use get_namespace().

To access values stored in this namespace use staticconf.readers or staticconf.schema.

clear() → None

Remove all values from the namespace.

get_config_dict() → Dict[str, Any]

Reconstruct the nested structure of this object’s configuration and return it as a dict.

get_config_values() → Dict[str, Any]

Return all configuration stored in this object as a dict.

class staticconf.config.ConfigurationWatcher(config_loader: Callable[[], Dict[str, Any]], filenames: Union[str, List[str]], min_interval: float = 0, reloader: Optional[Reloader] = None, comparators: Optional[List[Type[IComparator]]] = None)

Watches a file for modification and reloads the configuration when it’s modified. Accepts a min_interval to throttle checks.

The default reload() operation is to reload all namespaces. To only reload a specific namespace use a ReloadCallbackChain for the reloader.

See also

ConfigFacade.load() which provides a more concise interface for the common case.

Usage:

import staticconf
from staticconf import config

def build_configuration(filename, namespace):
    config_loader = partial(staticconf.YamlConfiguration,
                            filename, namespace=namespace)
    reloader = config.ReloadCallbackChain(namespace)
    return config.ConfigurationWatcher(
        config_loader, filename, min_interval=2, reloader=reloader)

config_watcher = build_configuration('config.yaml', 'my_namespace')

# Load the initial configuration
config_watcher.config_loader()

# Do some work
for item in work:
    config_watcher.reload_if_changed()
    ...

Parameters:

• config_loader – a function which takes no arguments. It is called by reload_if_changed() if the file has been modified

• filenames – a filename or list of filenames to watch for modifications

• min_interval – minimum number of seconds to wait between calls to os.path.getmtime() to check if a file has been modified.

• reloader – a function which is called after config_loader when a file has been modified. Defaults to an empty ReloadCallbackChain

• comparators – a list of classes which support the IComparator interface which are used to determine if a config file has been modified. Defaults to MTimeComparator.

reload_if_changed(force: bool = False) → Optional[Dict[str, Any]]

If the file(s) being watched by this object have changed, their configuration will be loaded again using config_loader. Otherwise this is a noop.

Parameters:

force – If True ignore the min_interval and proceed to file modified comparisons. To force a reload use reload() directly.

class staticconf.config.IComparator(filenames: List[str])

Interface for a comparator which is used by ConfigurationWatcher to determine if a file has been modified since the last check. A comparator is used to reduce the work required to reload configuration. Comparators should implement a mechanism that is relatively efficient (and scalable), so it can be performed frequently.

Parameters:

filenames – A list of absolute paths to configuration files.

has_changed() → bool

Returns True if any of the files have been modified since the last call to has_changed(). Returns False otherwise.

class staticconf.config.InodeComparator(filenames: List[str])

Compare files by inode and device number. This is a good comparator to use when your files can change multiple times per second.

has_changed() → bool

Returns True if any of the files have been modified since the last call to has_changed(). Returns False otherwise.

class staticconf.config.MD5Comparator(filenames: str)

Compare files by md5 hash of their contents. This comparator will be slower for larger files, but is more resilient to modifications which only change mtime, but not the files contents.

has_changed() → bool

Returns True if any of the files have been modified since the last call to has_changed(). Returns False otherwise.

class staticconf.config.MTimeComparator(filenames: List[str], compare_func: Optional[Callable[[str], bool]] = None)

Compare files by modified time, or using compare_func, if it is not None.

Note

Most filesystems only store modified time with second grangularity so multiple changes within the same second can be ignored.

has_changed() → bool

Returns True if any of the files have been modified since the last call to has_changed(). Returns False otherwise.

class staticconf.config.ReloadCallbackChain(namespace: str = 'DEFAULT', all_names: bool = False, callbacks: List[Tuple[str, Callable[[], None]]] = None)

A chain of callbacks which will be triggered after configuration is reloaded. Designed to work with ConfigurationWatcher.

When this class is called it performs two operations:

• calls reload() on the namespace

• calls all attached callbacks

Usage:

chain = ReloadCallbackChain()
chain.add('some_id', callback_foo)
chain.add('other_id', other_callback)
...

# some time later
chain.remove('some_id')

Parameters:

• namespace – the name of the namespace to reload()

• all_names – if True reload() all namespaces and ignore the namespace param. Defaults to False

• callbacks – initial list of tuples to add to the callback chain

staticconf.config.get_namespace(name: str) → ConfigNamespace

Return a ConfigNamespace by name, creating the namespace if it does not exist.

staticconf.config.reload(name: str = 'DEFAULT', all_names: bool = False) → None

Reload one or all ConfigNamespace. Reload clears the cache of staticconf.schema and staticconf.getters, allowing them to pickup the latest values in the namespace.

Defaults to reloading just the DEFAULT namespace.

Parameters:

• name – the name of the ConfigNamespace to reload

• all_names – If True, reload all namespaces, and ignore name

staticconf.config.validate(name: str = 'DEFAULT', all_names: bool = False) → None

Validate all registered keys after loading configuration.

Missing values or values which do not pass validation raise staticconf.errors.ConfigurationError. By default only validates the DEFAULT namespace.

Parameters:

• name (string) – the namespace to validate

• all_names (boolean) – if True validates all namespaces and ignores name

staticconf.config.view_help() → str

Return a help message describing all the statically configured keys.

Errors

exception staticconf.errors.ConfigurationError

Thrown when there is an error loading configuration from a file or object.

exception staticconf.errors.ValidationError

Thrown when a configuration value can not be coerced into the expected type by a validator.