#
# SPDX-License-Identifier: Apache-2.0
-from builtins import range
-from builtins import object
import functools
import inspect
import pycurl
import time
from collections import deque
+from typing import (
+ Callable,
+ Generic,
+ Optional,
+ TypeVar,
+)
import arvados.errors
_HTTP_SUCCESSES = set(range(200, 300))
_HTTP_CAN_RETRY = set([408, 409, 423, 500, 502, 503, 504])
-class RetryLoop(object):
+CT = TypeVar('CT', bound=Callable)
+T = TypeVar('T')
+
+class RetryLoop(Generic[T]):
"""Coordinate limited retries of code.
`RetryLoop` coordinates a loop that runs until it records a
Arguments:
- num_retries: int
- : The maximum number of times to retry the loop if it
- doesn't succeed. This means the loop body could run at most
+ * num_retries: int --- The maximum number of times to retry the loop if
+ it doesn't succeed. This means the loop body could run at most
`num_retries + 1` times.
- success_check: Callable
- : This is a function that will be called each
- time the loop saves a result. The function should return
- `True` if the result indicates the code succeeded, `False` if it
- represents a permanent failure, and `None` if it represents a
- temporary failure. If no function is provided, the loop will
- end after any result is saved.
-
- backoff_start: float
- : The number of seconds that must pass before the loop's second
- iteration. Default 0, which disables all waiting.
-
- backoff_growth: float
- : The wait time multiplier after each iteration.
- Default 2 (i.e., double the wait time each time).
-
- save_results: int
- : Specify a number to store that many saved results from the loop.
- These are available through the `results` attribute, oldest first.
- Default 1.
-
- max_wait: float
- : Maximum number of seconds to wait between retries. Default 60.
+ * success_check: Callable[[T], bool | None] --- This is a function that
+ will be called each time the loop saves a result. The function should
+ return `True` if the result indicates the code succeeded, `False` if
+ it represents a permanent failure, and `None` if it represents a
+ temporary failure. If no function is provided, the loop will end
+ after any result is saved.
+
+ * backoff_start: float --- The number of seconds that must pass before
+ the loop's second iteration. Default 0, which disables all waiting.
+
+ * backoff_growth: float --- The wait time multiplier after each
+ iteration. Default 2 (i.e., double the wait time each time).
+
+ * save_results: int --- Specify a number to store that many saved
+ results from the loop. These are available through the `results`
+ attribute, oldest first. Default 1.
+
+ * max_wait: float --- Maximum number of seconds to wait between
+ retries. Default 60.
"""
- def __init__(self, num_retries, success_check=lambda r: True,
- backoff_start=0, backoff_growth=2, save_results=1,
- max_wait=60):
+ def __init__(
+ self,
+ num_retries: int,
+ success_check: Callable[[T], Optional[bool]]=lambda r: True,
+ backoff_start: float=0,
+ backoff_growth: float=2,
+ save_results: int=1,
+ max_wait: float=60
+ ) -> None:
self.tries_left = num_retries + 1
self.check_result = success_check
self.backoff_wait = backoff_start
self._running = None
self._success = None
- def __iter__(self):
+ def __iter__(self) -> 'RetryLoop':
"""Return an iterator of retries."""
return self
- def running(self):
+ def running(self) -> Optional[bool]:
"""Return whether this loop is running.
Returns `None` if the loop has never run, `True` if it is still running,
"""
return self._running and (self._success is None)
- def __next__(self):
+ def __next__(self) -> int:
"""Record a loop attempt.
If the loop is still running, decrements the number of tries left and
self.tries_left -= 1
return self.tries_left
- def save_result(self, result):
+ def save_result(self, result: T) -> None:
"""Record a loop result.
Save the given result, and end the loop if it indicates
Arguments:
- result: Any
- : The result from this loop attempt to check and save.
+ * result: T --- The result from this loop attempt to check and save.
"""
if not self.running():
raise arvados.errors.AssertionError(
self._success = self.check_result(result)
self._attempts += 1
- def success(self):
+ def success(self) -> Optional[bool]:
"""Return the loop's end state.
Returns `True` if the loop recorded a successful result, `False` if it
"""
return self._success
- def last_result(self):
+ def last_result(self) -> T:
"""Return the most recent result the loop saved.
Raises `arvados.errors.AssertionError` if called before any result has
raise arvados.errors.AssertionError(
"queried loop results before any were recorded")
- def attempts(self):
+ def attempts(self) -> int:
"""Return the number of results that have been saved.
This count includes all kinds of results: success, permanent failure,
"""
return self._attempts
- def attempts_str(self):
+ def attempts_str(self) -> str:
"""Return a human-friendly string counting saved results.
This method returns '1 attempt' or 'N attempts', where the number
return '{} attempts'.format(self._attempts)
-def check_http_response_success(status_code):
+def check_http_response_success(status_code: int) -> Optional[bool]:
"""Convert a numeric HTTP status code to a loop control flag.
This method takes a numeric HTTP status code and returns `True` if
Arguments:
- status_code: int
- : A numeric HTTP response code
+ * status_code: int --- A numeric HTTP response code
"""
if status_code in _HTTP_SUCCESSES:
return True
else:
return None # Get well soon, server.
-def retry_method(orig_func):
+def retry_method(orig_func: CT) -> CT:
"""Provide a default value for a method's num_retries argument.
This is a decorator for instance and class methods that accept a
Arguments:
- orig_func: Callable
- : A class or instance method that accepts a `num_retries` keyword argument
+ * orig_func: Callable --- A class or instance method that accepts a
+ `num_retries` keyword argument
"""
@functools.wraps(orig_func)
def num_retries_setter(self, *args, **kwargs):
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