Modify data in existing whisper files to be derived from existing counter values

derived-value-migrate.py

#!/usr/bin/env python

import sys, time, whisper, shutil
from optparse import OptionParser

now = int( time.time() )

option_parser = OptionParser(
    usage='''%prog path from''')

(options, args) = option_parser.parse_args()

if len(args) != 2:
  option_parser.print_help()
  sys.exit(1)

path = args[0]
time_from = int(args[1])

time_info, points = whisper.fetch(path, time_from)

print "Processing %s" % path
shutil.copy(path, path + '.bak')

previous = None
timestamp = time_info[0]
new_points = [(time_info[0], 0)]

for value in points:
   if value and previous:
     difference = value - previous
     if difference < 0:
       break 
     else:
       new_points.append( (timestamp, difference) ) 
   else:
     new_points.append( (timestamp, 0) )
   previous = value 
   timestamp += time_info[2]

whisper.update_many(path, new_points)