Revision: 689
http://assorted.svn.sourceforge.net/assorted/?rev=689&view=rev
Author: yangzhang
Date: 2008-04-29 16:00:50 -0700 (Tue, 29 Apr 2008)
Log Message:
-----------
added retry_exp_backoff()
Modified Paths:
--------------
python-commons/trunk/src/commons/networking.py
Modified: python-commons/trunk/src/commons/networking.py
===================================================================
--- python-commons/trunk/src/commons/networking.py 2008-04-29 05:18:57 UTC (rev 688)
+++ python-commons/trunk/src/commons/networking.py 2008-04-29 23:00:50 UTC (rev 689)
@@ -6,6 +6,7 @@
"""
import os, sys
+from time import *
class NoMacAddrError( Exception ): pass
@@ -37,3 +38,28 @@
raise NoMacAddrError
return mac
+def retry_exp_backoff(initial_backoff, multiplier, func):
+ """
+ Repeatedly invoke L{func} until it succeeds (returns non-None), with
+ exponentially growing backoff delay between each try.
+
+ @param initial_backoff: The initial backoff.
+ @type initial_backoff: float
+
+ @param multiplier: The amount by which the backoff is multiplied on each
+ failure.
+ @type multiplier: float
+
+ @param func: The zero-argument function to be invoked that returns True on
+ success and False on failure.
+ @type func: function
+
+ @return: The result of the function
+ """
+ backoff = initial_backoff
+ while True:
+ res = func()
+ if res is not None: return res
+ print 'backing off for', backoff
+ sleep(backoff)
+ backoff = multiplier * backoff
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