A silverstripe type daemon example

Daemon.php

<?php

/**
 * This is an example of daemon that runs for a set period of time and the quits. It only allows one task at time
 * by using a PID file
 * 
 * The scripts have a few timers that might need explaining
 * 
 * First there are the $this->anotherInstanceRunning($this->timeout) that checks if a process haven't updated the
 * pidfile in $this->timeout seconds, then we declare it as dead and start the task, otherwise it quits.
 * 
 * Secondly is that the script will in daemon mode only run for $lifetime sec before terminating. This is 
 * to make sure that the script doesnt hog up to much resources and also if we do a deploy or so.
 * 
 * At can be run in browser, from command line as:
 * /dev/tasks/Daemon
 *
 * Or from cronjobs with a less expressive output as:
 * /dev/tasks/Daemon verbose=1
 * 
 * Or for running it in the crontab this is the recommended way.
 *
   * * * * * /path/to/site/sapphire/sake dev/tasks/Daemon daemon=1 verbose=0 >> /tmp/output.log
 *
 */
class Daemon extends BuildTask {

	/**
	* After how many seconds should a task be regarded as dead?
	*
	* @var int
	*/
	protected $timeout = 30;
	
	/**
	*
	* @var int
	*/
	protected $lifetime = 590;

	/**
	 *
	 * @var string
	 */
	protected $title = "Daemon";
	
	/**
	 *
	 * @var string
	 */
	protected $description = "Run something for a time then quit";
	
	/**
	 * Marks if the task should be chatty. Can be used for less outpug when running
	 * cronjobs.
	 *
	 * @var boolean
	 */
	protected $verbose = false;

	/**
	 * Starts the daemon
	 *
	 * @var $request SS_HTTPRequest
	*/
	public function run($request) {
        	if($request->getVar('verbose')) {
		        $this->verbose = true;
		}
		
		$currentlyRunningInfo = $this->anotherInstanceRunning($this->timeout);
		if(is_array($currentlyRunningInfo)) {
			if($this->verbose) {
				echo 'Another task is running with pid '.$currentlyRunningInfo[0].' last heard of '.$currentlyRunningInfo[1].' seconds ago.'.PHP_EOL;
			}
			return;
		}
		
		// no daemon mode run once then quit
		if(!$request->getVar('daemon')) {
			$this->execute();
			$this->removePid();
			return;
		} 

		while($this->execute() && $this->hasRunLessThan($this->lifetime)) {
			// sleep one second
			sleep(1);
		}
	}
	
	/**
	 *
	 * @return boolean - if this task should be run again
	 */
	protected function execute() {
		$this->updatePid();
		// do somework
		echo 'doing some work'.PHP_EOL;
		return true;
	}

	/**
	 * Return an boolean to see if this class has run more than x seconds and
	 * then return true;
	 *
	 * @param int $seconds
	 * @return boolean
	 */
	protected function hasRunLessThan( $seconds ) {
		return $this->runningTime() < $seconds;
	}

	/**
	 * Check if another instance is running with the regard to a timelimit.
	 *
	 * @var int $secondsBeforeDead
	 * @return bool or array
	 */
	protected function anotherInstanceRunning($secondsBeforeDead) {
		$pidRawdata = $this->getPid();
		if(!$pidRawdata) {
			return false;
		}
		$pidInfo = explode(PHP_EOL, $pidRawdata);
				// Is it this task that is still running, then it's alright
		if($pidInfo[2] == getmypid()) {
			return false;
		}
		$pidSecondsSince=(time()-$pidInfo[0]);
		// Most likely a dead process, log and return false;
		if($pidSecondsSince > $secondsBeforeDead  ) {
			echo ('Aha, dead process started to stink '.$pidSecondsSince.' seconds ago, restarting.'.PHP_EOL);
			return false;
		}
		return array($pidInfo[2],$pidSecondsSince);
	}

	/**
	 * Adds information to the pid file
	 *
	 * @param float $microtime
	 * @return void
	 */
	protected function updatePid() {
		$seconds = time();
        	$fp = fopen($this->getPidFilePath(), "w+");
        	if(!flock($fp, LOCK_EX | LOCK_NB)) {
        		throw new Exception('Can\'t get flock() on "'.$this->getPidFilePath().'"', $code, $previous);
        	}
        	$pidMessage = $seconds.PHP_EOL.date('Y-m-d H:i:s',$seconds).PHP_EOL.getmypid().PHP_EOL;
        	fputs($fp, $pidMessage, strlen($pidMessage));
        	flock($fp, LOCK_UN);
        	fclose($fp);
	}

	/**
	 * Delete the pidfile
	 *
	 */
	protected function removePid() {
		if(!is_file($this->getPidFilePath())) {
			return;
		}
		unlink($this->getPidFilePath());
	}

	/**
	 * Get the contents of the pid file
	 *
	 * @return string
	 */
	protected function getPid() {
		if(is_readable($this->getPidFilePath())) {
			return trim(file_get_contents($this->getPidFilePath()));
		}
		return '';
	}

	/**
	 * Get the absolute path to the pidfile
	 *
	 * @return string
	 */
	protected function getPidFilePath() {
		return getTempFolder() . DIRECTORY_SEPARATOR . 'pid.'.strtolower(__CLASS__).'.txt';
	}

	/**
	 * Returns the number of seconds since first calling this function
	 *
	 * @return int - seconds
	 */
	protected function runningTime() {
		static $start_time = 0;
		if(!$start_time) {
			$start_time = time();
		}
		return time() - $start_time;
	}
}