custom-prometheus-exporter/index.php

<?php
require 'vendor/autoload.php';
$configFile = getenv('CONFIG_FILE') ?: 'config.php';
$cacheFile = $configFile . '.cache.json';

if (file_exists($configFile)) {
    require ($configFile);
} else {
    echo ("Configuration file not found: " . $configFile);
    exit(1);
}
if(file_exists($cacheFile)) {
    $oldconfig = json_decode(file_get_contents($cacheFile), true);
} else {
    $oldconfig = [];
}

if(php_sapi_name() == 'cli' || $_SERVER["REQUEST_URI"] == '/metrics') {
    header('Content-Type: text/plain; version=0.0.4');
    foreach ($config as $key => &$metric) {
        if (!isset($metric['submetrics'])) {
            $metric['submetrics'] = [$metric];
        }
        foreach ($metric['submetrics'] as $subkey => &$submetric) {
            $pid = pcntl_fork();
            if ($pid > 0) {
                $pids[] = $pid;
            } else {
                if (isset($submetric['command'])) {
                    $output = null;
                    $retval = null;
                    try {
                        exec($submetric['command'], $output, $retval);
                        $output = implode("\n", $output);
                    } catch (Exception $e) {
                        $output = '';
                    }
                } elseif (isset($submetric['http'])) {
                    $client = new GuzzleHttp\Client();

                    $options = [];
                    $output = NULL;
                    if (isset($submetric['http']['proxy'])) {
                        $options['proxy'] = $submetric['http']['proxy'];
                    }
                    if (isset($submetric['http']['data']) && $submetric['http']['data'] == 'responsetime') {
                        $options['on_stats'] = function (GuzzleHttp\TransferStats $stats) use (&$output) {
                            $output = $stats->getTransferTime();
                        };
                    }

                    $hasresponse = NULL;
                    try {
                        $res = $client->request('GET', $submetric['http']['url'], $options);
                        $hasresponse = true;
                    } catch (GuzzleHttp\Exception\GuzzleException $e) {
                        if (method_exists($e, 'getResponse')) {
                            $res = $e->getResponse();
                            $hasresponse = true;
                        } else {
                            $hasresponse = false;
                        }
                    }

                    if (isset($submetric['http']['data']) && $submetric['http']['data'] == 'responsebody') {
                        if ($hasresponse) {
                            $output = $res->getBody()->getContents();
                        } else {
                            $output = '';
                        }
                    } elseif ((isset($submetric['http']['statuscode'])) && (isset($submetric['http']['data']) && $submetric['http']['data'] == 'hasresponse')) {
                        if ($hasresponse) {
                            $output = $output = (int)in_array($res->getStatusCode(), $submetric['http']['statuscode']);;
                        } else {
                            $output = 0;
                        }
                    } elseif (isset($submetric['http']['data']) && $submetric['http']['data'] == 'hasresponse') {
                        $output = (int)$hasresponse;
                    }
                }

                if (isset($submetric['jsonelem'])) {
                    $submetric['value'] = getArrayValue($submetric['jsonelem'], json_decode($output, true));
                } else {
                    $submetric['value'] = $output;
                }

                if (is_bool($submetric['value'])) $submetric['value'] = $submetric['value'] ? 1 : 0;

                file_put_contents('/tmp/.metrics.' . $key . '.' . $subkey, $submetric['value']);
                exit();
            }
        }
    }
    foreach ($pids as $pid) {
        pcntl_waitpid($pid, $none);
    }


    foreach ($config as $key => &$metric) {
        foreach ($metric['submetrics'] as $subkey => &$submetric) {
            $submetric['value'] = file_get_contents('/tmp/.metrics.' . $key . '.' . $subkey);
            if (!empty($oldconfig) && !isset($submetric['value']) && (isset($submetric['fallback']) && !empty($submetric['fallback']))) {
                if (!isset($submetric['fallback']['maxage']) || time() < ($oldconfig[$key]['submetrics'][$subkey]['time'] + $submetric['fallback']['maxage'])) {
                    if ($submetric['fallback']['type'] == 'previous') {
                        $submetric['value'] = $oldconfig[$key]['submetrics'][$subkey]['value'];
                    } elseif ($submetric['fallback']['type'] == 'static') {
                        $submetric['value'] = $submetric['fallback']['value'];
                    }
                    $submetric['time'] = $oldconfig[$key]['submetrics'][$subkey]['time'];
                } else {
                    $submetric['value'] = '';
                    $submetric['time'] = 0;
                }
            } else {
                $submetric['time'] = time();
            }
            unlink('/tmp/.metrics.' . $key . '.' . $subkey);
        }
    }

    file_put_contents($cacheFile, json_encode($config, JSON_PRETTY_PRINT));

    $loader = new \Twig\Loader\FilesystemLoader('templates');
    $twig = new \Twig\Environment($loader, [
        'cache' => 'twig_cache',
    ]);
    echo $twig->render('metrics.twig', ['config' => $config]);
}

function getArrayValue($elem, $array) {
    $elem = explode('.', $elem);
    $new_array = $array;
    foreach ($elem as $i) {
        if(empty($new_array)) break;
        $new_array = $new_array[$i];
    }
    return $new_array;
}