Health check with memory monitoring of Elastic Beanstalk instance and push to CloudWatch (SDK v2)

health.php

<?php

namespace Curved\Health;

use Aws\CloudWatch\CloudWatchClient;

require __DIR__ . '/../vendor/autoload.php';

class HealthInfo
{

    /**
     * @var Aws\CloudWatch\CloudWatchClient
     */
    private $client;

    /**
     * @var String
     */
    private $instanceId;

    /**
     * WARNING: Only works on linux!
     */
    const MEMORY_INFO_FILE = '/proc/meminfo';

    const MEM_TOTAL = 'MemTotal';
    const MEM_FREE = 'MemFree';
    const MEM_USAGE = 'Usage';
    const MEM_PUSH = 'MetricPush';

    const ERR_FETCH = 'Unable to fetch memory information';

    /**
     * HealthInfo constructor.
     */
    public function __construct()
    {
        $this->client = CloudWatchClient::factory([
            'profile' => 'default',
            'region' => 'eu-central-1',
            'version' => '2010-08-01'
        ]);

        $this->instanceId = $this->getInstanceId();
    }

    /**
     * Try to figure out the ec2 instance ID
     *
     * @return string
     */
    private function getInstanceId()
    {
        // Default so we know its wrong but still value
        $instanceId = 'empty';

        $instanceInformation = file_get_contents('http://169.254.169.254/latest/dynamic/instance-identity/document');

        if (!$instanceInformation) {
            return $instanceId;
        }
        // More info on https://stackoverflow.com/questions/625644/how-to-get-the-instance-id-from-within-an-ec2-instance/19912843
        $instance = json_decode($instanceInformation,true);

        if (isset($instance['instanceId'])) {
            $instanceId = $instance['instanceId'];
        }

        return $instanceId;
    }

    /**
     * @return array|string
     */
    private function getSystemMemInfo()
    {
        $memoryInfo = [];

        try {
            $usage = $this->getMemoryUsage();
            $memoryInfo[self::MEM_USAGE] = $usage;

            $result = $this->client->putMetricData(array(
                'Namespace' => 'Portal Application',
                'MetricData' => array(
                    array(
                        'MetricName' => 'FreeMemory',
                        'Dimensions' => [
                            [
                                'Name' => 'InstanceId',
                                'Value' => $this->instanceId,
                            ],
                        ],
                        'Timestamp' => time(),
                        'Value' => $usage,
                        'Unit' => 'Percent'

                    )
                )
            ));

            $memoryInfo[self::MEM_PUSH] = $result;
        } catch (\Exception $e) {
            $memoryInfo[self::MEM_PUSH] = $e->getMessage();
        }
        return $memoryInfo;
    }

    /**
     * @return float|int
     * @throws \Exception
     */
    private function getMemoryUsage()
    {
        if (!file_exists(self::MEMORY_INFO_FILE)) {
            throw new \Exception(self::ERR_FETCH . ' :: File does not exists: ' . self::MEMORY_INFO_FILE);
        }

        $file = file_get_contents(self::MEMORY_INFO_FILE);

        if (!$file) {
            throw new \Exception(self::ERR_FETCH . ' :: File could not be opened: ' . self::MEMORY_INFO_FILE);
        }
        $data = explode("\n", $file);
        $parsedData = [];
        foreach ($data as $line) {
            $keyValue = explode(":", $line);
            if (count($keyValue) < 2) continue; // To be sure there is key / value within a row
            list($key, $val) = $keyValue;
            $parsedData[$key] = trim($val);
        }
        if (!isset($parsedData[self::MEM_TOTAL]) || !isset($parsedData[self::MEM_FREE])) {
            throw new \Exception(self::ERR_FETCH . ' :: Data unavailable.');
        }

        $total = $parsedData[self::MEM_TOTAL];
        $free = $parsedData[self::MEM_FREE];

        return round((100 / $total) * $free);
    }

    /**
     * @return false|mixed|string|void
     */
    public function report()
    {
        $report = [
            'status' => 'OK',
            'system' => [
                'instanceId' => $this->instanceId,
                'memory' => $this->getSystemMemInfo(),
            ],
        ];

        return json_encode($report);
    }
}

$info = new HealthInfo();
echo $info->report();