circuitbreaker.CircuitBreaker.__enter__() - Code Metrics - Inspection of "Merge pull request #16 from AugPro/develop" - fabfuel/circuitbreaker - Measure and Improve Code Quality continuously with Scrutinizer

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by Fabian

created 2021-01-23 07:16 UTC

circuitbreaker.CircuitBreaker.enter() A

↳ Parent: circuitbreaker

Complexity

Conditions

Size

Total Lines	2
Code Lines	2

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	0
CRAP Score	2

Importance

Changes

Metric	Value
cc	1
eloc	2
nop	1
dl	0
loc	2
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

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 = datetime.utcnow()

    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 genrator 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 = datetime.utcnow()

    @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 datetime, when the circuit breaker will try to recover
        :return: datetime
        """
        return self._opened + timedelta(seconds=self._recovery_timeout)

    @property
    def open_remaining(self):
        """
        Number of seconds remaining, the circuit breaker stays in OPEN state
        :return: int
        """
        return (self.open_until - datetime.utcnow()).total_seconds()

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

fabfuel / circuitbreaker

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circuitbreaker.CircuitBreaker.__enter__() A

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