NAME Try::Tiny::Retry - Extends Try::Tiny to allow retries VERSION version 0.002 SYNOPSIS Use just like Try::Tiny, but with "retry" instead of "try". By default, "retry" will try 10 times with exponential backoff: use Try::Tiny::Retry; retry { ... } catch { ... } finally { ... }; You can retry only if the error matches some conditions: use Try::Tiny::Retry; retry { ... } retry_if { /^could not connect/ } catch { ... }; You can customize the number of tries and delay timing: use Try::Tiny::Retry ':all'; retry { ... } delay_exp { 5, 1e6 } # 5 tries, 1 second exponential-backoff catch { ... }; You can run some code before each retry: use Try::Tiny::Retry; retry { ... } on_retry { ... } catch { ... }; DESCRIPTION This module extends Try::Tiny to allow for retrying a block of code several times before failing. Otherwise, it works seamlessly like Try::Tiny. By default, Try::Tiny::Retry exports "retry" and "retry_if", plus "try", "catch" and "finally" from Try::Tiny. You can optionally export "delay" or "delay_exp". Or you can get everything with the ":all" tag. FUNCTIONS retry retry { ... } # code that might fail retry_if { ... } # conditions to be met for a retry delay { ... } # control repeats and intervals between retries catch { ... }; # handler if all retries fail The "retry" function works just like "try" from Try::Tiny, except that if an exception is thrown, the block may be executed again, depending on the "retry_if" and "delay" blocks. By default, if no "retry_if" blocks are provided, retries depend only on the "delay" block. If no "delay" block is provided, the default will be 10 tries with a random delay up to 100 milliseconds with an exponential backoff. (See "delay_exp".) This has an expected cumulative delay of around 25 seconds if all retries fail. retry_if retry { ... } retry_if { /^could not connect/ } catch { ... }; A "retry_if" block controls whether a retry should be attempted. The block is passed the cumulative number of attempts as an argument. The exception caught is provided in $_, just as with "catch". It should return a true value if a retry should be attempted. Multiple "retry_if" blocks may be provided. Only one needs to evaluate to true to enable a retry. Using a "retry_if" block based on the retry count is an alternate way to allow fewer (but not greater) tries than the default "delay" function, but with the default exponential backoff behavior. These are effectively equivalent: retry { ... } retry_if { shift() < 3 }; retry { ... } delay_exp { 3, 1e5 }; on_retry retry { ... } on_retry { $state->reset() } catch { ... }; The "on_retry" block runs before each "retry" block after the first attempt. The block is passed the cumulative number of attempts as an argument. The return value is ignored. Only one "on_retry" block is allowed. delay retry { ... } delay { return if $_[0] >= 3; # only three tries sleep 1; # constant delay between tries } catch { ... }; The "delay" block is executed when the "retry" block throws an exception to determine if a retry should be attempted and to manage the delay between attempts. The block is passed the cumulative number of attempts as an argument. If the "delay" block returns an undefined value, no further retries will be made and the most recent exception will be rethrown. Only one "delay" block is allowed. delay_exp retry { ... } delay_exp { 3, 10000 } # 3 tries, 10000 µsec catch { ... }; This function is an exponential-backoff delay-function generator. The delay between attempts is randomly selected between 0 and an upper bound. The upper bound doubles after each failure. It requires a code block as an argument. The block will be evaluated in list context and must return two elements. The first element is the number of tries allowed. The second element is the starting upper bound in microseconds. Given number of tries "N" and upper bound "U", the expected cumulative delay time if all attempts fail is "0.5 * U * ( 2^(N-1) - 1 )". SEE ALSO There are other retry modules on CPAN, but none of them worked seamlessly with Try::Tiny. * Action::Retry — OO (Moo) or functional; various delay strategies; supports conditions * AnyEvent::Retry — OO (Moose) and event-driven; various delay strategies * Attempt — functional; simple retry count with constant sleep time * Retry — OO (Moose) with fixed exponential backoff; supports callbacks on every iteration * Sub::Retry — functional; simple retry count with constant sleep time; supports conditions SUPPORT Bugs / Feature Requests Please report any bugs or feature requests through the issue tracker at . You will be notified automatically of any progress on your issue. Source Code This is open source software. The code repository is available for public review and contribution under the terms of the license. git clone https://github.com/dagolden/Try-Tiny-Retry.git AUTHOR David Golden COPYRIGHT AND LICENSE This software is Copyright (c) 2013 by David Golden. This is free software, licensed under: The Apache License, Version 2.0, January 2004