Find peak in value of an RRDtool base.

rrd_peak_find.py

import rrdtool
import datetime

# retrieve RRD data (3 days past from now)
rrd = rrdtool.fetch('/home/pi/rrd/flow.rrd', 'AVERAGE', '-s -3d')

# timestamp start/end
start = rrd[0][0]
end   = rrd[0][1]
step  = rrd[0][2]
# array of data
data = rrd[2]
# c is current value, last_c is c at cycle -1
c = None
last_c = None

def ts2str(timestamp):
  return datetime.datetime.fromtimestamp(timestamp).strftime('%Y-%m-%d %H:%M:%S')

# start/stop timestamp banner
print("start: %d (%s), end %d (%s)" %(start, ts2str(start), end, ts2str(end)))
print("")

# display only value with high change rate
for i, item in enumerate(data):
  if item[0] is not None:
    c = item[0]
    if last_c is None:
      last_c = c

    chg_rate = 100*abs(c - last_c)/c

    # display value if change rate more than 10%
    if (chg_rate > 10.0):
      tstamp = (i*step) + start
      print("%s: %f (%.1f%% last %.2f)" % (ts2str(tstamp), item[0], chg_rate, last_c))

    last_c = c