class SDLWrapper:
"""
- This is a wrapper around the SDL Python interface.
+ Provides convenient wrapper methods for using the SDL Python interface.
+ Optionally uses msgpack for binary (de)serialization:
+ see https://msgpack.org/index.html
- We do not embed the below directly in the Xapp classes because
- this SDL wrapper is useful for other python apps, for example A1
- Mediator uses this verbatim. Therefore, we leave this here as a
- seperate instantiable object so it can be used outside of xapps
- too. One could argue this get moved into *sdl itself*.
-
- We currently use msgpack for binary (de)serialization:
- https://msgpack.org/index.html
+ Published as a standalone module (and kept separate from the Xapp
+ framework classes) so these features can be used outside Xapps.
"""
def __init__(self, use_fake_sdl=False):
Parameters
----------
- use_fake_sdl: bool
- if this is True (default: False), then SDLs "fake dict
- backend" is used, which is very useful for testing since
- it allows you to use SDL without any SDL or Redis deployed at
- all. This can be used while developing your xapp, and also
- for monkeypatching during unit testing (e.g., the xapp
- framework unit tests do this).
+ use_fake_sdl: bool (optional, default False)
+ if this is True, then use SDL's in-memory backend,
+ which is very useful for testing since it allows use
+ of SDL without a running SDL or Redis instance.
+ This can be used while developing an xapp and also
+ for monkeypatching during unit testing; e.g., the xapp
+ framework unit tests do this.
"""
if use_fake_sdl:
self._sdl = SyncStorage(fake_db_backend="dict")
def set(self, ns, key, value, usemsgpack=True):
"""
- sets a key
+ Stores a key-value pair,
+ optionally serializing the value to bytes using msgpack.
TODO: discuss whether usemsgpack should *default* to True or
False here. This seems like a usage statistic question (that we
don't have enough data for yet). Are more uses for an xapp to
write/read their own data, or will more xapps end up reading data
- written by some other thing? I think it's too early to know
- this. So we go with True as the very first user of this, a1, does
- this. I'm open to changing this default to False later with
- evidence.
+ written by some other thing? I think it's too early to know.
Parameters
----------
ns: string
- the sdl namespace
+ SDL namespace
key: string
- the sdl key
+ SDL key
value:
- if usemsgpack is True, value can be anything serializable by msgpack
- if usemsgpack is False, value must be bytes
- usemsgpack: boolean (optional)
- determines whether the value is serialized using msgpack
+ Object or byte array to store. See the `usemsgpack` parameter.
+ usemsgpack: boolean (optional, default is True)
+ Determines whether the value is serialized using msgpack before storing.
+ If usemsgpack is True, the msgpack function `packb` is invoked
+ on the value to yield a byte array that is then sent to SDL.
+ Stated differently, if usemsgpack is True, the value can be anything
+ that is serializable by msgpack.
+ If usemsgpack is False, the value must be bytes.
"""
if usemsgpack:
- self._sdl.set(ns, {key: msgpack.packb(value, use_bin_type=True)})
- else:
- self._sdl.set(ns, {key: value})
+ value = msgpack.packb(value, use_bin_type=True)
+ self._sdl.set(ns, {key: value})
def get(self, ns, key, usemsgpack=True):
"""
- get a key
+ Gets the value for the specified namespace and key,
+ optionally deserializing stored bytes using msgpack.
Parameters
----------
ns: string
- the sdl namespace
+ SDL namespace
key: string
- the sdl key
- usemsgpack: boolean (optional)
- if usemsgpack is True, the value is deserialized using msgpack
- if usemsgpack is False, the value is returned as raw bytes
+ SDL key
+ usemsgpack: boolean (optional, default is True)
+ If usemsgpack is True, the byte array stored by SDL is deserialized
+ using msgpack to yield the original object that was stored.
+ If usemsgpack is False, the byte array stored by SDL is returned
+ without further processing.
Returns
-------
- None (if not exist) or see above; depends on usemsgpack
+ Value
+ See the usemsgpack parameter for an explanation of the returned value type.
+ Answers None if the key is not found.
"""
+ result = None
ret_dict = self._sdl.get(ns, {key})
if key in ret_dict:
+ result = ret_dict[key]
if usemsgpack:
- return msgpack.unpackb(ret_dict[key], raw=False)
- return ret_dict[key]
-
- return None
+ result = msgpack.unpackb(result, raw=False)
+ return result
def find_and_get(self, ns, prefix, usemsgpack=True):
"""
- get all k v pairs that start with prefix
+ Gets all key-value pairs in the specified namespace
+ with keys that start with the specified prefix,
+ optionally deserializing stored bytes using msgpack.
Parameters
----------
ns: string
- the sdl namespace
- key: string
- the sdl key
+ SDL namespace
prefix: string
- the prefix
- usemsgpack: boolean (optional)
- if usemsgpack is True, the value returned is a dict where each value has been deserialized using msgpack
- if usemsgpack is False, the value returned is as a dict mapping keys to raw bytes
+ the key prefix
+ usemsgpack: boolean (optional, default is True)
+ If usemsgpack is True, every byte array stored by SDL is deserialized
+ using msgpack to yield the original value that was stored.
+ If usemsgpack is False, every byte array stored by SDL is returned
+ without further processing.
Returns
-------
- {} (if no keys match) or see above; depends on usemsgpack
+ Dictionary of key-value pairs
+ Each key has the specified prefix.
+ See the usemsgpack parameter for an explanation of the returned value types.
+ Answers an empty dictionary if no keys matched the prefix.
"""
# note: SDL "*" usage is inconsistent with real python regex, where it would be ".*"
ret_dict = self._sdl.find_and_get(ns, "{0}*".format(prefix))
if usemsgpack:
- return {k: msgpack.unpackb(v, raw=False) for k, v in ret_dict.items()}
+ ret_dict = {k: msgpack.unpackb(v, raw=False) for k, v in ret_dict.items()}
return ret_dict
def delete(self, ns, key):
"""
- delete a key
+ Deletes the key-value pair with the specified key in the specified namespace.
Parameters
----------
ns: string
- the sdl namespace
+ SDL namespace
key: string
- the sdl key
+ SDL key
"""
self._sdl.remove(ns, {key})
def healthcheck(self):
"""
- checks if the sdl connection is healthy
+ Checks if the sdl connection is healthy.
Returns
-------
Code Review / ric-plt / xapp-frame-py.git / blobdiff