Munin 没有绘制：“NaN”

Question

我为 munin 编写了一个插件，它基本上从 .log 文件中提取一些数字并计算这些值的平均值。

当我使用 munin-cron 或直接像这样运行它时：

# munin-run latency_news 
latency.value 0.1

# ./latency_news
latency.value 0.1

它运行得很好。但在我的 html munin 页面中，我只看到图表中的所有值都是“Nan”：

（该图片仅供展示，并非我的实际插件）

这是插件的代码：

#!/usr/bin/env php
<?php

class LatencyLog
{
    private $fname;
    private $fd;
    private $pname;
    private $pos;
    function __construct($page)
    {
        $this->fname = '/var/log/time_'.$page.'.log';
        if (!($this->fd = @fopen($this->fname, 'r')))
        {
            throw new Exception('Unable to read ' . $this->fname);
        }
        $this->pname = $this->fname;
        $this->pos = 0;
        if ($pd = @fopen($this->pname, 'r'))
        {
            $pos = (int) fgets($pd);
            fclose($pd);
            fseek($this->fd, 0, SEEK_END);
            if ($pos <= ftell($this->fd))
            {
                $this->pos = $pos;
            }
        }
        fseek($this->fd, $this->pos);
    }
    function __destruct()
    {
        $pos = ftell($this->fd);
        if ($pos != $this->pos)
        {
            if (!($pd = @fopen($this->pname, 'w')))
            {
                throw new Exception('Unable to write ' . $this->pname);
            }
            fprintf($pd, "%d\n", $pos);
            fclose($pd);
        }
        fclose($this->fd);
    }
    function get_line()
    {
        return fgets($this->fd);
    }
}

class LatencyMonitor
{
    private $query_log;
    private $page;
    function __construct()
    {
        $this->page = explode('_', $_SERVER['SCRIPT_FILENAME']);
        $this->query_log = new LatencyLog($this->page[1]);
    }
    function check($what)
    {
        $queries = 0;
        $results = 0;
        $times = 0;
        while ($line = $this->query_log->get_line())
        {
            $url = explode('=', $line);
            $page = $url[0];
            if ($page == $this->page[1])
            {
                $queries++;
                $times += (float) $url[1];
            }
        }
        if ($queries > 0)
            $times /= $queries;
        echo "$what.value ".str_replace(',', '.', round($times, 2))."\n";
    }
}

$tmp = explode('_', $_SERVER['SCRIPT_FILENAME']);
$name = $tmp[1];
$label = 'average time per query';
$what = 'latency';

if (isset($argv[1]))
{
    if ($argv[1] == 'config')
    {
        $title = $name;
        echo "graph_title $title\n";
        echo "graph_category perfs\n";
        echo "graph_vlabel $label\n";
        echo "$what.label $what\n";
        echo "$what.type GAUGE\n";
        echo "$what.min 0\n";
        exit;
    }
}

$smm = new LatencyMonitor();
$smm->check($what);
?>