ganeti.utils.retry

module documentation

Utility functions for retrying function calls with a timeout.

Exception	`RetryAgain`	Retry again.
Exception	`RetryTimeout`	Retry loop timed out.
Function	`CountRetry`	A wrapper over `SimpleRetry` implementing a count down.
Function	`Retry`	Call a function repeatedly until it succeeds.
Function	`RetryByNumberOfTimes`	Retries calling a function up to the specified number of times.
Function	`SimpleRetry`	A wrapper over `Retry` implementing a simpler interface.
Constant	`RETRY_REMAINING_TIME`	Undocumented
Class	`_RetryDelayCalculator`	Calculator for increasing delays.

def CountRetry(expected, fn, count, args=None): ¶

A wrapper over SimpleRetry implementing a count down.

Where Retry fixes the time, after which the command is assumed to be failing, this function assumes the total number of tries.

See Also
`Retry`

def Retry(fn, delay, timeout, args=None, wait_fn=time.sleep, _time_fn=time.time): ¶

Call a function repeatedly until it succeeds.

The function fn is called repeatedly until it doesn't throw RetryAgain anymore. Between calls a delay, specified by delay, is inserted. After a total of timeout seconds, this function throws RetryTimeout.

delay can be one of the following:

callable returning the delay length as a float
Tuple of (start, factor, limit)
RETRY_REMAINING_TIME to sleep until the timeout expires (this is useful when overriding wait_fn to wait for an external event)
A static delay as a number (int or float)

Parameters
fn:callable	Function to be called
delay	Either a callable (returning the delay), a tuple of (start, factor, limit) (see `_RetryDelayCalculator`), `RETRY_REMAINING_TIME` or a number (int or float)
timeout:float	Total timeout
args	Undocumented
wait_fn:callable	Waiting function
_time_fn	Undocumented
Returns
Return value of function

def RetryByNumberOfTimes(max_retries, exception_class, fn, *args, **kwargs): ¶

Retries calling a function up to the specified number of times.

Parameters
max_retries:integer	Maximum number of retries.
exception_class:class	Exception class which is used for throwing the final exception.
fn:callable	Function to be called (up to the specified maximum number of retries.
*args	Undocumented
**kwargs	Undocumented

def SimpleRetry(expected, fn, delay, timeout, args=None, wait_fn=time.sleep, _time_fn=time.time): ¶

A wrapper over Retry implementing a simpler interface.

All the parameters are the same as for Retry, except it has one extra argument: expected, which can be either a value (will be compared with the result of the function, or a callable (which will get the result passed and has to return a boolean). If the test is false, we will retry until either the timeout has passed or the tests succeeds. In both cases, the last result from calling the function will be returned.

Note that this function is not expected to raise any retry-related exceptions, always simply returning values. As such, the function is designed to allow easy wrapping of code that doesn't use retry at all (e.g. "if fn(args)" replaced with "if SimpleRetry(True, fn, ...)".

See Also
`Retry`

RETRY_REMAINING_TIME = ¶

Undocumented

Value

object()