import importlib
import sys
from functools import wraps
from inspect import isfunction
from random import random
from time import sleep
from types import FunctionType, WrapperDescriptorType
from typing import Any, Callable, Dict, Sequence, Type, Union, no_type_check
[docs]class TopicError(Exception):
"""
Raised when topic doesn't resolve.
"""
_type_cache: Dict[type, str] = {}
_topic_cache: Dict[str, Any] = {}
[docs]def get_topic(cls: type) -> str:
"""
Returns a "topic string" that locates the given class
in its module. The string is formed by joining the
module name and the class qualname separated by the
colon character.
"""
try:
return _type_cache[cls]
except KeyError:
topic = f"{cls.__module__}:{cls.__qualname__}"
_topic_cache[topic] = cls
return topic
[docs]def resolve_topic(topic: str) -> Any:
"""
Returns an object located by the given topic.
This function can be (is) used to locate domain
event classes and aggregate classes from the
topics in stored events and snapshots. It can
also be used to locate compression modules,
timezone objects, etc.
"""
try:
obj = _topic_cache[topic]
except KeyError:
module_name, _, attr_name = topic.partition(":")
attr_name_parts = attr_name.split(".")
for i in range(len(attr_name_parts) - 1, 0, -1):
part_name = ".".join(attr_name_parts[:i])
try:
obj = _topic_cache[f"{module_name}:{part_name}"]
except KeyError:
continue
else:
attr_name = ".".join(attr_name_parts[i:])
break
else:
try:
obj = _topic_cache[module_name]
except KeyError:
module_name_parts = module_name.split(".")
for i in range(len(module_name_parts) - 1, 0, -1):
part_name = ".".join(module_name_parts[:i])
try:
obj = _topic_cache[f"{part_name}"]
except KeyError:
continue
else:
module_name = ".".join([obj.__name__] + module_name_parts[i:])
break
try:
obj = importlib.import_module(module_name)
except ImportError as e:
raise TopicError from e
if attr_name:
for attr_name_part in attr_name.split("."):
try:
obj = getattr(obj, attr_name_part)
except AttributeError as e:
raise TopicError from e
register_topic(topic, obj)
return obj
[docs]def register_topic(topic: str, obj: Any) -> None:
"""
Registers a topic with an object, so the object will be
returned whenever the topic is resolved.
This function can be used to cache the topic of a class, so
that the topic can be resolved faster. It can also be used to
register old topics for objects that have been renamed or moved,
so that old topics will resolve to the renamed or moved object.
"""
if topic in _topic_cache:
raise TopicError("Topic is already registered")
_topic_cache[topic] = obj
[docs]def retry(
exc: Union[Type[Exception], Sequence[Type[Exception]]] = Exception,
max_attempts: int = 1,
wait: float = 0,
stall: float = 0,
) -> Callable[[Any], Any]:
"""
Retry decorator.
:param exc: List of exceptions that will cause the call to be retried if raised.
:param max_attempts: Maximum number of attempts to try.
:param wait: Amount of time to wait before retrying after an exception.
:param stall: Amount of time to wait before the first attempt.
:param verbose: If True, prints a message to STDOUT when retries occur.
:return: Returns the value returned by decorated function.
"""
@no_type_check
def _retry(func):
@wraps(func)
def wrapper(*args, **kwargs):
if stall:
sleep(stall)
attempts = 0
while True:
try:
return func(*args, **kwargs)
except exc as e:
attempts += 1
if max_attempts is None or attempts < max_attempts:
sleep(wait * (1 + 0.1 * (random() - 0.5)))
else:
# Max retries exceeded.
raise e
return wrapper
# If using decorator in bare form, the decorated
# function is the first arg, so check 'exc'.
if isfunction(exc):
# Remember the given function.
_func = exc
# Set 'exc' to a sensible exception class for _retry().
exc = Exception
# Wrap and return.
return _retry(func=_func)
else:
# Check decorator args, and return _retry,
# to be called with the decorated function.
if isinstance(exc, (list, tuple)):
for _exc in exc:
if not (isinstance(_exc, type) and issubclass(_exc, Exception)):
raise TypeError("not an exception class: {}".format(_exc))
else:
if not (isinstance(exc, type) and issubclass(exc, Exception)):
raise TypeError("not an exception class: {}".format(exc))
if not isinstance(max_attempts, int):
raise TypeError("'max_attempts' must be an int: {}".format(max_attempts))
if not isinstance(wait, (float, int)):
raise TypeError("'wait' must be a float: {}".format(max_attempts))
if not isinstance(stall, (float, int)):
raise TypeError("'stall' must be a float: {}".format(max_attempts))
return _retry
[docs]def strtobool(val: str) -> bool:
"""Convert a string representation of truth to True or False.
True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
are 'n', 'no', 'f', 'false', 'off', and '0'. Raises ValueError if
'val' is anything else.
"""
if not isinstance(val, str):
raise TypeError(f"{val} is not a str")
val = val.lower()
if val in ("y", "yes", "t", "true", "on", "1"):
return True
elif val in ("n", "no", "f", "false", "off", "0"):
return False
else:
raise ValueError("invalid truth value %r" % (val,))
def is_py310() -> bool:
return sys.version_info[0:2] == (3, 10)
def get_method_name(method: Union[FunctionType, WrapperDescriptorType]) -> str:
return is_py310() and method.__qualname__ or method.__name__