今天將介紹使用RRDTool來繪製系統負荷的Python程式.
程式碼如下:

#!/usr/bin/env python
# ---------------------------
# Python RRDTool 
# LoadAvg Data
# Create Image from rrd file
# ---------------------------

import rrdtool
import datetime

def load_graph(rrdfile, load, period):
    timenow = datetime.datetime.now()
    disptime = datetime.datetime.strftime(timenow, '%Y-%m-%d %H-%M-%S')
    if period == 'yesterday':
        start = 'end-1d'
        end = '00:00'
    if period == 'today':
        start = '00:00'
        end = '23:59'
    title = '%s_avg_%s' % (load, period)
    filename = title + '.png'
    def_load = 'DEF:%s=%s:%s:AVERAGE' % (load, rrdfile, load)
    if load == 'load1':
        graph_cmd = 'AREA:%s#8985BF: 1 min average' % load
    if load == 'load5':
        graph_cmd = 'AREA:%s#F4888B: 5 min average' % load
    if load == 'load15':
        graph_cmd = 'AREA:%s#EAEF66: 15 min average' % load
    last_print = 'GPRINT:%s' % load
    last_print = last_print + ':LAST:  Current\\: %4.2lf' 
    
    avg_print = 'GPRINT:%s:' % load
    avg_print = avg_print + 'AVERAGE:   Average\\: %4.2lf' 
    min_print = 'GPRINT:%s' % load
    min_print = min_print + ':MIN:   Min\\: %4.2lf' 
    max_print = 'GPRINT:%s' % load
    max_print = max_print + ':MAX:   Max\\: %4.2lf\\n' 
    # -------------------
           
    rrdtool.graph(
        filename,
        '--start', start,
        '--end', end,
        '--title', title,
        '-a', 'PNG',
        '-W', 'Hitomitanaka for ITHelp',
        '--slope-mode',
        '--vertical-label=Load Average',
        '--rigid',
        '--upper-limit', '3',
        '--lower-limit', '0',
        '--width', '500',
        '--height', '150',
        '--x-grid', 'HOUR:1:HOUR:2:HOUR:2:0:%H',
        '--alt-y-grid',
        '--color', 'BACK#000000',
        '--color', 'CANVAS#000000',
        '--color', 'FONT#FFF978',
        '--font=LEGEND:7',
        '--font', 'TITLE:8:',
        '--font', 'UNIT:7:',
        '--font', 'WATERMARK:9',
        # ---------------------------------
        def_load,
        graph_cmd,
        last_print,
        avg_print,
        min_print,
        max_print,
        'COMMENT:\t\t\t\tUpdate Time %s' % disptime)
#

def draw_loads(period):
    load_graph('sysload.rrd', 'load1', period)
    load_graph('sysload.rrd', 'load5', period)
    load_graph('sysload.rrd', 'load15', period)
    


if __name__ == '__main__':
    draw_loads('today')

匯製的圖形如下:
一分鐘平均負荷:

五分鐘平均負荷:

十五分鐘平均負荷:

除了匯製 時間-數值 圖形以外,底下還有例出 現在值,平均值,最大值,最小值,
方便對系統負荷有一個整體的概觀.