[Assorted-commits] SF.net SVN: assorted: [689] python-commons/trunk/src/commons/networking.py

[<yan...@us...>]

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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