circuitbreaker.CircuitBreakerMonitor.get_circuits() - Code Metrics - Inspection of "Add GitHub actions workflow" - fabfuel/circuitbreaker - Measure and Improve Code Quality continuously with Scrutinizer

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Pull Request — develop (#34)

by Fabian

created 2022-03-13 06:32 UTC

CircuitBreakerMonitor.get_circuits() A

↳ Parent: circuitbreaker

Complexity

Conditions

Size

Total Lines	4
Code Lines	3

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	0
CRAP Score	2

Importance

Changes

Metric	Value
cc	1
eloc	3
nop	1
dl	0
loc	4
ccs	0
cts	0
cp	0
crap	2
rs	10
c	0
b	0
f	0

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from __future__ import division
from __future__ import print_function
from __future__ import absolute_import

from functools import wraps
from datetime import datetime, timedelta
from inspect import isgeneratorfunction
from typing import AnyStr, Iterable
from math import ceil, floor

try:
  from time import monotonic
except ImportError:
  from monotonic import monotonic

STATE_CLOSED = 'closed'
STATE_OPEN = 'open'
STATE_HALF_OPEN = 'half_open'


class CircuitBreaker(object):
    FAILURE_THRESHOLD = 5
    RECOVERY_TIMEOUT = 30
    EXPECTED_EXCEPTION = Exception
    FALLBACK_FUNCTION = None

    def __init__(self,
                 failure_threshold=None,
                 recovery_timeout=None,
                 expected_exception=None,
                 name=None,
                 fallback_function=None):
        self._last_failure = None
        self._failure_count = 0
        self._failure_threshold = failure_threshold or self.FAILURE_THRESHOLD
        self._recovery_timeout = recovery_timeout or self.RECOVERY_TIMEOUT
        self._expected_exception = expected_exception or self.EXPECTED_EXCEPTION
        self._fallback_function = fallback_function or self.FALLBACK_FUNCTION
        self._name = name
        self._state = STATE_CLOSED
        self._opened = monotonic()

    def __call__(self, wrapped):
        return self.decorate(wrapped)

    def __enter__(self):
        return None

    def __exit__(self, exc_type, exc_value, _traceback):
        if exc_type and issubclass(exc_type, self._expected_exception):
            # exception was raised and is our concern
            self._last_failure = exc_value
            self.__call_failed()
        else:
            self.__call_succeeded()
        return False  # return False to raise exception if any

    def decorate(self, function):
        """
        Applies the circuit breaker to a function
        """
        if self._name is None:
            self._name = function.__name__

        CircuitBreakerMonitor.register(self)

        if isgeneratorfunction(function):
            call = self.call_generator
        else:
            call = self.call

        @wraps(function)
        def wrapper(*args, **kwargs):
            if self.opened:
                if self.fallback_function:
                    return self.fallback_function(*args, **kwargs)
                raise CircuitBreakerError(self)
            return call(function, *args, **kwargs)

        return wrapper

    def call(self, func, *args, **kwargs):
        """
        Calls the decorated function and applies the circuit breaker
        rules on success or failure
        :param func: Decorated function
        """
        with self:
            return func(*args, **kwargs)

    def call_generator(self, func, *args, **kwargs):
        """
        Calls the decorated generator function and applies the circuit breaker
        rules on success or failure
        :param func: Decorated generator function
        """
        with self:
            for el in func(*args, **kwargs):
                yield el

    def __call_succeeded(self):
        """
        Close circuit after successful execution and reset failure count
        """
        self._state = STATE_CLOSED
        self._last_failure = None
        self._failure_count = 0

    def __call_failed(self):
        """
        Count failure and open circuit, if threshold has been reached
        """
        self._failure_count += 1
        if self._failure_count >= self._failure_threshold:
            self._state = STATE_OPEN
            self._opened = monotonic()

    @property
    def state(self):
        if self._state == STATE_OPEN and self.open_remaining <= 0:
            return STATE_HALF_OPEN
        return self._state

    @property
    def open_until(self):
        """
        The approximate datetime when the circuit breaker will try to recover
        :return: datetime
        """
        return datetime.utcnow() + timedelta(seconds=self.open_remaining)

    @property
    def open_remaining(self):
        """
        Number of seconds remaining, the circuit breaker stays in OPEN state
        :return: int
        """
        remain = (self._opened + self._recovery_timeout) - monotonic()
        return ceil(remain) if remain > 0 else floor(remain)

    @property
    def failure_count(self):
        return self._failure_count

    @property
    def closed(self):
        return self.state == STATE_CLOSED

    @property
    def opened(self):
        return self.state == STATE_OPEN

    @property
    def name(self):
        return self._name

    @property
    def last_failure(self):
        return self._last_failure

    @property
    def fallback_function(self):
        return self._fallback_function

    def __str__(self, *args, **kwargs):
        return self._name


class CircuitBreakerError(Exception):
    def __init__(self, circuit_breaker, *args, **kwargs):
        """
        :param circuit_breaker:
        :param args:
        :param kwargs:
        :return:
        """
        super(CircuitBreakerError, self).__init__(*args, **kwargs)
        self._circuit_breaker = circuit_breaker

    def __str__(self, *args, **kwargs):
        return 'Circuit "%s" OPEN until %s (%d failures, %d sec remaining) (last_failure: %r)' % (
            self._circuit_breaker.name,
            self._circuit_breaker.open_until,
            self._circuit_breaker.failure_count,
            round(self._circuit_breaker.open_remaining),
            self._circuit_breaker.last_failure,
        )


class CircuitBreakerMonitor(object):
    circuit_breakers = {}

    @classmethod
    def register(cls, circuit_breaker):
        cls.circuit_breakers[circuit_breaker.name] = circuit_breaker

    @classmethod
    def all_closed(cls):
        # type: () -> bool
        return len(list(cls.get_open())) == 0

    @classmethod
    def get_circuits(cls):
        # type: () -> Iterable[CircuitBreaker]
        return cls.circuit_breakers.values()

    @classmethod
    def get(cls, name):
        # type: (AnyStr) -> CircuitBreaker
        return cls.circuit_breakers.get(name)

    @classmethod
    def get_open(cls):
        # type: () -> Iterable[CircuitBreaker]
        for circuit in cls.get_circuits():
            if circuit.opened:
                yield circuit

    @classmethod
    def get_closed(cls):
        # type: () -> Iterable[CircuitBreaker]
        for circuit in cls.get_circuits():
            if circuit.closed:
                yield circuit


def circuit(failure_threshold=None,
            recovery_timeout=None,
            expected_exception=None,
            name=None,
            fallback_function=None,
            cls=CircuitBreaker):

    # if the decorator is used without parameters, the
    # wrapped function is provided as first argument
    if callable(failure_threshold):
        return cls().decorate(failure_threshold)
    else:
        return cls(
            failure_threshold=failure_threshold,
            recovery_timeout=recovery_timeout,
            expected_exception=expected_exception,
            name=name,
            fallback_function=fallback_function)


1		# -- coding: utf-8 --
2	1	from __future__ import unicode_literals
3	1	from __future__ import division
4	1	from __future__ import print_function
5	1	from __future__ import absolute_import
6
7	1	from functools import wraps
8	1	from datetime import datetime, timedelta
9	1	from inspect import isgeneratorfunction
10		from typing import AnyStr, Iterable
11	1	from math import ceil, floor
12	1
13	1	try:
14		from time import monotonic
15		except ImportError:
16	1	from monotonic import monotonic
17	1
18	1	STATE_CLOSED = 'closed'
19	1	STATE_OPEN = 'open'
20	1	STATE_HALF_OPEN = 'half_open'
21
22	1
23		class CircuitBreaker(object):
24		FAILURE_THRESHOLD = 5
25		RECOVERY_TIMEOUT = 30
26		EXPECTED_EXCEPTION = Exception
27		FALLBACK_FUNCTION = None
28	1
29	1	def __init__(self,
30	1	failure_threshold=None,
31	1	recovery_timeout=None,
32	1	expected_exception=None,
33	1	name=None,
34	1	fallback_function=None):
35	1	self._last_failure = None
36	1	self._failure_count = 0
37		self._failure_threshold = failure_threshold or self.FAILURE_THRESHOLD
38	1	self._recovery_timeout = recovery_timeout or self.RECOVERY_TIMEOUT
39	1	self._expected_exception = expected_exception or self.EXPECTED_EXCEPTION
40		self._fallback_function = fallback_function or self.FALLBACK_FUNCTION
41	1	self._name = name
42		self._state = STATE_CLOSED
43		self._opened = monotonic()
44
45	1	def __call__(self, wrapped):
46	1	return self.decorate(wrapped)
47
48	1	def __enter__(self):
49		return None
50	1
51		def __exit__(self, exc_type, exc_value, _traceback):
52	1	if exc_type and issubclass(exc_type, self._expected_exception):
53		# exception was raised and is our concern
54	1	self._last_failure = exc_value
55		self.__call_failed()
56	1	else:
57		self.__call_succeeded()
58		return False # return False to raise exception if any
59
60		def decorate(self, function):
61		"""
62	1	Applies the circuit breaker to a function
63	1	"""
64	1	if self._name is None:
65	1	self._name = function.__name__
66	1
67	1	CircuitBreakerMonitor.register(self)
68	1
69	1	if isgeneratorfunction(function):
70	1	call = self.call_generator
71	1	else:
72		call = self.call
73	1
74	1	@wraps(function)
75		def wrapper(args, *kwargs):
76	1	if self.opened:
77		if self.fallback_function:
78		return self.fallback_function(args, *kwargs)
79		raise CircuitBreakerError(self)
80	1	return call(function, args, *kwargs)
81	1
82	1	return wrapper
83
84	1	def call(self, func, args, *kwargs):
85		"""
86		Calls the decorated function and applies the circuit breaker
87		rules on success or failure
88	1	:param func: Decorated function
89	1	"""
90	1	with self:
91	1	return func(args, *kwargs)
92
93	1	def call_generator(self, func, args, *kwargs):
94		"""
95	1	Calls the decorated generator function and applies the circuit breaker
96	1	rules on success or failure
97	1	:param func: Decorated generator function
98		"""
99	1	with self:
100		for el in func(args, *kwargs):
101		yield el
102
103		def __call_succeeded(self):
104		"""
105	1	Close circuit after successful execution and reset failure count
106		"""
107	1	self._state = STATE_CLOSED
108		self._last_failure = None
109		self._failure_count = 0
110
111		def __call_failed(self):
112		"""
113	1	Count failure and open circuit, if threshold has been reached
114		"""
115	1	self._failure_count += 1
116		if self._failure_count >= self._failure_threshold:
117	1	self._state = STATE_OPEN
118		self._opened = monotonic()
119	1
120		@property
121	1	def state(self):
122		if self._state == STATE_OPEN and self.open_remaining <= 0:
123	1	return STATE_HALF_OPEN
124		return self._state
125	1
126		@property
127	1	def open_until(self):
128		"""
129	1	The approximate datetime when the circuit breaker will try to recover
130		:return: datetime
131	1	"""
132		return datetime.utcnow() + timedelta(seconds=self.open_remaining)
133	1
134		@property
135	1	def open_remaining(self):
136		"""
137	1	Number of seconds remaining, the circuit breaker stays in OPEN state
138		:return: int
139	1	"""
140	1	remain = (self._opened + self._recovery_timeout) - monotonic()
141		return ceil(remain) if remain > 0 else floor(remain)
142
143	1	@property
144	1	def failure_count(self):
145		return self._failure_count
146
147		@property
148		def closed(self):
149		return self.state == STATE_CLOSED
150
151	1	@property
152	1	def opened(self):
153		return self.state == STATE_OPEN
154	1
155	1	@property
156		def name(self):
157		return self._name
158
159		@property
160		def last_failure(self):
161		return self._last_failure
162
163		@property
164	1	def fallback_function(self):
165	1	return self._fallback_function
166
167	1	def __str__(self, args, *kwargs):
168		return self._name
169	1
170
171	1	class CircuitBreakerError(Exception):
172		def __init__(self, circuit_breaker, args, *kwargs):
173		"""
174	1	:param circuit_breaker:
175		:param args:
176	1	:param kwargs:
177		:return:
178		"""
179	1	super(CircuitBreakerError, self).__init__(args, *kwargs)
180		self._circuit_breaker = circuit_breaker
181	1
182		def __str__(self, args, *kwargs):
183		return 'Circuit "%s" OPEN until %s (%d failures, %d sec remaining) (last_failure: %r)' % (
184	1	self._circuit_breaker.name,
185		self._circuit_breaker.open_until,
186	1	self._circuit_breaker.failure_count,
187		round(self._circuit_breaker.open_remaining),
188		self._circuit_breaker.last_failure,
189	1	)
190	1
191	1
192		class CircuitBreakerMonitor(object):
193	1	circuit_breakers = {}
194
195		@classmethod
196	1	def register(cls, circuit_breaker):
197	1	cls.circuit_breakers[circuit_breaker.name] = circuit_breaker
198	1
199		@classmethod
200		def all_closed(cls):
201	1	# type: () -> bool
202		return len(list(cls.get_open())) == 0
203
204		@classmethod
205		def get_circuits(cls):
206		# type: () -> Iterable[CircuitBreaker]
207		return cls.circuit_breakers.values()
208
209		@classmethod
210	1	def get(cls, name):
211	1	# type: (AnyStr) -> CircuitBreaker
212		return cls.circuit_breakers.get(name)
213	1
214		@classmethod
215		def get_open(cls):
216		# type: () -> Iterable[CircuitBreaker]
217		for circuit in cls.get_circuits():
218		if circuit.opened:
219		yield circuit
220
221		@classmethod
222		def get_closed(cls):
223		# type: () -> Iterable[CircuitBreaker]
224		for circuit in cls.get_circuits():
225		if circuit.closed:
226		yield circuit
227
228
229		def circuit(failure_threshold=None,
230		recovery_timeout=None,
231		expected_exception=None,
232		name=None,
233		fallback_function=None,
234		cls=CircuitBreaker):
235
236		# if the decorator is used without parameters, the
237		# wrapped function is provided as first argument
238		if callable(failure_threshold):
239		return cls().decorate(failure_threshold)
240		else:
241		return cls(
242		failure_threshold=failure_threshold,
243		recovery_timeout=recovery_timeout,
244		expected_exception=expected_exception,
245		name=name,
246		fallback_function=fallback_function)
247

fabfuel / circuitbreaker

Pull Request — develop (#34)

CircuitBreakerMonitor.get_circuits() A

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