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Help on module arvados.retry in arvados:
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NNAAMMEE
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arvados.retry - Utilities to retry operations.
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DDEESSCCRRIIPPTTIIOONN
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The core of this module is `RetryLoop`, a utility class to retry operations
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that might fail. It can distinguish between temporary and permanent failures;
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provide exponential backoff; and save a series of results.
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It also provides utility functions for common operations with `RetryLoop`:
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* `check_http_response_success` can be used as a `RetryLoop` `success_check`
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for HTTP response codes from the Arvados API server.
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* `retry_method` can decorate methods to provide a default `num_retries`
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keyword argument.
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CCLLAASSSSEESS
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builtins.object
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RetryLoop
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class RReettrryyLLoooopp(builtins.object)
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| RetryLoop(num_retries, success_check=<function RetryLoop.<lambda> at 0x7fcbac047790>, backoff_start=0, backoff_growth=2, save_results=1, max_wait=60)
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| Coordinate limited retries of code.
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| `RetryLoop` coordinates a loop that runs until it records a
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| successful result or tries too many times, whichever comes first.
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| Typical use looks like:
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| loop = RetryLoop(num_retries=2)
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| for tries_left in loop:
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| try:
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| result = do_something()
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| except TemporaryError as error:
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| log("error: {} ({} tries left)".format(error, tries_left))
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| else:
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| loop.save_result(result)
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| if loop.success():
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| return loop.last_result()
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| Arguments:
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| num_retries: int
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| : The maximum number of times to retry the loop if it
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| doesn't succeed. This means the loop body could run at most
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| `num_retries + 1` times.
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| success_check: Callable
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| : This is a function that will be called each
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| time the loop saves a result. The function should return
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| `True` if the result indicates the code succeeded, `False` if it
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| represents a permanent failure, and `None` if it represents a
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| temporary failure. If no function is provided, the loop will
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| end after any result is saved.
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| backoff_start: float
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| : The number of seconds that must pass before the loop's second
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| iteration. Default 0, which disables all waiting.
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| backoff_growth: float
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| : The wait time multiplier after each iteration.
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| Default 2 (i.e., double the wait time each time).
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| save_results: int
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| : Specify a number to store that many saved results from the loop.
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| These are available through the `results` attribute, oldest first.
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| Default 1.
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| max_wait: float
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| : Maximum number of seconds to wait between retries. Default 60.
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| Methods defined here:
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| ____iinniitt____(self, num_retries, success_check=<function RetryLoop.<lambda> at 0x7fcbac047790>, backoff_start=0, backoff_growth=2, save_results=1, max_wait=60)
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| Initialize self. See help(type(self)) for accurate signature.
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| ____iitteerr____(self)
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| Return an iterator of retries.
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| ____nneexxtt____(self)
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| Record a loop attempt.
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| If the loop is still running, decrements the number of tries left and
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| returns it. Otherwise, raises `StopIteration`.
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| aatttteemmppttss(self)
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| Return the number of results that have been saved.
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| This count includes all kinds of results: success, permanent failure,
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| and temporary failure.
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| aatttteemmppttss__ssttrr(self)
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| Return a human-friendly string counting saved results.
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| !!! deprecated
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| This method is deprecated. Use your favorite localization library
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| instead.
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| This is a demonstration notice for illustration. I do think we
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| should probably deprecate this method, but not as part of this
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| branch.
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| This method returns '1 attempt' or 'N attempts', where the number
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| in the string is the number of saved results.
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| llaasstt__rreessuulltt(self)
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| Return the most recent result the loop saved.
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| Raises `arvados.errors.AssertionError` if called before any result has
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| been saved.
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| rruunnnniinngg(self)
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| Return whether this loop is running.
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| Returns `None` if the loop has never run, `True` if it is still running,
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| or `False` if it has stopped—whether that's because it has saved a
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| successful result, a permanent failure, or has run out of retries.
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| ssaavvee__rreessuulltt(self, result)
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| Record a loop result.
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| Save the given result, and end the loop if it indicates
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| success or permanent failure. See documentation for the `__init__`
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| `success_check` argument to learn how that's indicated.
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| Raises `arvados.errors.AssertionError` if called after the loop has
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| already ended.
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| Arguments:
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| result: Any
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| : The result from this loop attempt to check and save.
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| ssuucccceessss(self)
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| Return the loop's end state.
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| Returns `True` if the loop recorded a successful result, `False` if it
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| recorded permanent failure, or else `None`.
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| ----------------------------------------------------------------------
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| Data descriptors defined here:
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| ____ddiicctt____
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| dictionary for instance variables (if defined)
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| ____wweeaakkrreeff____
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| list of weak references to the object (if defined)
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FFUUNNCCTTIIOONNSS
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cchheecckk__hhttttpp__rreessppoonnssee__ssuucccceessss(status_code)
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Convert a numeric HTTP status code to a loop control flag.
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This method takes a numeric HTTP status code and returns `True` if
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the code indicates success, `None` if it indicates temporary
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failure, and `False` otherwise. You can use this as the
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`success_check` for a `RetryLoop` that queries the Arvados API server.
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Specifically:
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* Any 2xx result returns `True`.
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* A select few status codes, or any malformed responses, return `None`.
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422 Unprocessable Entity is in this category. This may not meet the
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letter of the HTTP specification, but the Arvados API server will
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use it for various server-side problems like database connection
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errors.
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* Everything else returns `False`. Note that this includes 1xx and
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3xx status codes. They don't indicate success, and you can't
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retry those requests verbatim.
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Arguments:
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status_code: int
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: A numeric HTTP response code
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rreettrryy__mmeetthhoodd(orig_func)
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Provide a default value for a method's num_retries argument.
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This is a decorator for instance and class methods that accept a
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`num_retries` keyword argument, with a `None` default. When the method
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is called without a value for `num_retries`, this decorator will set it
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from the `num_retries` attribute of the underlying instance or class.
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Arguments:
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orig_func: Callable
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: A class or instance method that accepts a `num_retries` keyword argument
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FFIILLEE
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/home/brett/Curii/arvados/sdk/python/arvados/retry.py
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