RRD起步3——用脚本包装RRDtool(译)

by：ysuncn（欢迎转载，请注明译者）

        理解了RRDtool之后该开始用脚本来使用RRDtool 了，网络管理相关的任务是：数据收集、数据存储和数据提取，下边的例子中，使用了“RRD起步1——通过例子理解RRD”中的target.rrd，为了方便，重新show一下：

rrdtool create target.rrd /
        --start 1023654125 /
        --step 300 /
        DS:mem:GAUGE:600:0:671744 /
        RRA:AVERAGE:0.5:12:24 /
        RRA:AVERAGE:0.5:288:31

        数据收集和数据存储通过shell脚本完成，数据的提取和报告的生成通过perl脚本完成。脚本如下：

shell脚本（数据采集，更新数据库）
#!/bin/sh
a=0
while [ "$a" == 0 ]; do
snmpwalk -c public 192.168.1.250 hrSWRunPerfMem > snmp_reply
    total_mem=`awk 'BEGIN {tot_mem=0}
                          { if ($NF == "KBytes")
                            {tot_mem=tot_mem+$(NF-1)}
                          }
                    END {print tot_mem}' snmp_reply`
    # I can use N as a replacement for the current time
    rrdtool update target.rrd N:$total_mem
    # sleep until the next 300 seconds are full
    perl -e 'sleep 300 - time % 300'
done # end of while loop

perl脚本（从数据库提取数据，生成图片和统计信息）
#!/usr/bin/perl -w
# This script fetches data from target.rrd, creates a graph of memory
# consumption on the target (Dual P3 Processor 1 GHz, 656 MB RAM)

# call the RRD perl module
use lib qw( /usr/local/rrdtool-1.0.41/lib/perl ../lib/perl );
use RRDs;
my $cur_time = time();                # set current time
my $end_time = $cur_time - 86400;     # set end time to 24 hours ago
my $start_time = $end_time - 2592000; # set start 30 days in the past

# fetch average values from the RRD database between start and end time
my ($start,$step,$ds_names,$data) =
    RRDs::fetch("target.rrd", "AVERAGE",
                "-r", "600", "-s", "$start_time", "-e", "$end_time");
# save fetched values in a 2-dimensional array
my $rows = 0;
my $columns = 0;
my $time_variable = $start;
foreach $line (@$data) {
  $vals[$rows][$columns] = $time_variable;
  $time_variable = $time_variable + $step;
  foreach $val (@$line) {
          $vals[$rows][++$columns] = $val;}
  $rows++;
  $columns = 0;
}
my $tot_time = 0;
my $count = 0;
# save the values from the 2-dimensional into a 1-dimensional array
for $i ( 0 .. $#vals ) {
    $tot_mem[$count] = $vals[$i][1];
    $count++;
}
my $tot_mem_sum = 0;
# calculate the total of all values
for $i ( 0 .. ($count-1) ) {
    $tot_mem_sum = $tot_mem_sum + $tot_mem[$i];
}
# calculate the average of the array
my $tot_mem_ave = $tot_mem_sum/($count);
# create the graph
RRDs::graph ("/images/mem_$count.png",   /
            "--title= Memory Usage",    /
            "--vertical-label=Memory Consumption (MB)", /
            "--start=$start_time",      /
            "--end=$end_time",          /
            "--color=BACK#CCCCCC",      /
            "--color=CANVAS#CCFFFF",    /
            "--color=SHADEB#9999CC",    /
            "--height=125",             /
            "--upper-limit=656",        /
            "--lower-limit=0",          /
            "--rigid",                  /
            "--base=1024",              /
            "DEF:tot_mem=target.rrd:mem:AVERAGE", /
            "CDEF:tot_mem_cor=tot_mem,0,671744,LIMIT,UN,0,tot_mem,IF,1024,/",/
            "CDEF:machine_mem=tot_mem,656,+,tot_mem,-",/
            "COMMENT:Memory Consumption between $start_time",/
            "COMMENT:    and $end_time                     ",/
            "HRULE:656#000000:Maximum Available Memory - 656 MB",/
            "AREA:machine_mem#CCFFFF:Memory Unused",   /
            "AREA:tot_mem_cor#6699CC:Total memory consumed in MB");
my $err=RRDs::error;
if ($err) {print "problem generating the graph: $err/n";}
# print the output
print "Average memory consumption is ";
printf "%5.2f",$tot_mem_ave/1024;
print " MB. Graphical representation can be found at /images/mem_$count.png.";

ps：代码小长了一点r，不懂脚本是无法使用RRDtool的，入门的例子相对都经典一点，希望耐心品味。