Puts current system load into cloudwatch. Uses a lock file as created by Kevin Traas here; http://php.net/manual/en/function.getmypid.php

LogLoad.php

#!/usr/bin/php
<?php

define('LOCK_FILE', "/var/run/".basename( $argv[0], ".php" ).".lock" );
if( isLocked() ) die( "Already running.\n" );

# The rest of your script goes here....
require 'vendor/autoload.php';

use Aws\Common\Aws;

$aws = Aws::factory();

$load = sys_getloadavg();

use Aws\CloudWatch\CloudWatchClient;

$conf = array(
  "key" => "key",
  "secret" => "secret",
  "region" => "ap-southeast-2"
);

$client = CloudWatchClient::factory($conf);

  $guzzle = new Guzzle\Http\Client();
  // Get our instance deets
  $request = $guzzle->get('http://169.254.169.254/latest/meta-data/instance-id');
  $response = $request->send();
  $instanceId = $response->getBody(true);

  $client->putMetricData(array(
    'Namespace' => 'NS',
    'MetricData' => array(
      array(
        'MetricName' => 'NSLoad',
        'Value' => (float) $load[0],
        'Timestamp' => time(),
        'Unit' => 'None',
        'Dimensions' => array(
          array('Name' => 'InstanceId', 'Value' => $instanceId),
          array('Name' => 'AutoScalingGroupName', 'Value' => 'SNSWebGroup'),
        ),
      ),
    )
  ));

unlink( LOCK_FILE );
exit(0);

function isLocked()
{
    # If lock file exists, check if stale.  If exists and is not stale, return TRUE
    # Else, create lock file and return FALSE.

    if( file_exists( LOCK_FILE ) )
    {
        # check if it's stale
        $lockingPID = trim( file_get_contents( LOCK_FILE ) );

       # Get all active PIDs.
        $pids = explode( "\n", trim( `ps -e | awk '{print $1}'` ) );

        # If PID is still active, return true
        if( in_array( $lockingPID, $pids ) )  return true;

        # Lock-file is stale, so kill it.  Then move on to re-creating it.
        echo "Removing stale lock file.\n";
        unlink( LOCK_FILE );
    }

    file_put_contents( LOCK_FILE, getmypid() . "\n" );
    return false;

}