分享PHP守护进程类

用PHP实现的Daemon类。可以在服务器上实现队列或者脱离 crontab 的计划任务。 
使用的时候，继承于这个类，并重写 _doTask 方法，通过 main 初始化执行。

<?php

class Daemon {

  const DLOG_TO_CONSOLE = 1;
  const DLOG_NOTICE = 2;
  const DLOG_WARNING = 4;
  const DLOG_ERROR = 8;
  const DLOG_CRITICAL = 16;

  const DAPC_PATH = '/tmp/daemon_apc_keys';

  /**
   * User ID
   *
   * @var int
   */
  public $userID = 65534; // nobody

  /**
   * Group ID
   *
   * @var integer
   */
  public $groupID = 65533; // nobody

  /**
   * Terminate daemon when set identity failure ?
   *
   * @var bool
   * @since 1.0.3
   */
  public $requireSetIdentity = false;

  /**
   * Path to PID file
   *
   * @var string
   * @since 1.0.1
   */
  public $pidFileLocation = '/tmp/daemon.pid';

  /**
   * processLocation
   * 进程信息记录目录
   *
   * @var string
   */
  public $processLocation = '';

  /**
   * processHeartLocation
   * 进程心跳包文件
   *
   * @var string
   */
  public $processHeartLocation = '';

  /**
   * Home path
   *
   * @var string
   * @since 1.0
   */
  public $homePath = '/';

  /**
   * Current process ID
   *
   * @var int
   * @since 1.0
   */
  protected $_pid = 0;

  /**
   * Is this process a children
   *
   * @var boolean
   * @since 1.0
   */
  protected $_isChildren = false;

  /**
   * Is daemon running
   *
   * @var boolean
   * @since 1.0
   */
  protected $_isRunning = false;

  /**
   * Constructor
   *
   * @return void
   */
  public function __construct() {

    error_reporting(0);
    set_time_limit(0);
    ob_implicit_flush();

    register_shutdown_function(array(&$this, 'releaseDaemon'));
  }

  /**
   * 启动进程
   *
   * @return bool
   */
  public function main() {

    $this->_logMessage('Starting daemon');

    if (!$this->_daemonize()) {
      $this->_logMessage('Could not start daemon', self::DLOG_ERROR);

      return false;
    }

    $this->_logMessage('Running...');

    $this->_isRunning = true;

    while ($this->_isRunning) {
      $this->_doTask();
    }

    return true;
  }

  /**
   * 停止进程
   *
   * @return void
   */
  public function stop() {

    $this->_logMessage('Stoping daemon');

    $this->_isRunning = false;
  }

  /**
   * Do task
   *
   * @return void
   */
  protected function _doTask() {
    // override this method
  }

  /**
   * _logMessage
   * 记录日志
   *
   * @param string 消息
   * @param integer 级别
   * @return void
   */
  protected function _logMessage($msg, $level = self::DLOG_NOTICE) {
    // override this method
  }

  /**
   * Daemonize
   *
   * Several rules or characteristics that most daemons possess:
   * 1) Check is daemon already running
   * 2) Fork child process
   * 3) Sets identity
   * 4) Make current process a session laeder
   * 5) Write process ID to file
   * 6) Change home path
   * 7) umask(0)
   *
   * @access private
   * @since 1.0
   * @return void
   */
  private function _daemonize() {

    ob_end_flush();

    if ($this->_isDaemonRunning()) {
      // Deamon is already running. Exiting
      return false;
    }

    if (!$this->_fork()) {
      // Coudn't fork. Exiting.
      return false;
    }

    if (!$this->_setIdentity() && $this->requireSetIdentity) {
      // Required identity set failed. Exiting
      return false;
    }

    if (!posix_setsid()) {
      $this->_logMessage('Could not make the current process a session leader', self::DLOG_ERROR);

      return false;
    }

    if (!$fp = fopen($this->pidFileLocation, 'w')) {
      $this->_logMessage('Could not write to PID file', self::DLOG_ERROR);
      return false;
    } else {
      fputs($fp, $this->_pid);
      fclose($fp);
    }

    // 写入监控日志
    $this->writeProcess();

    chdir($this->homePath);
    umask(0);

    declare(ticks = 1);

    pcntl_signal(SIGCHLD, array(&$this, 'sigHandler'));
    pcntl_signal(SIGTERM, array(&$this, 'sigHandler'));
    pcntl_signal(SIGUSR1, array(&$this, 'sigHandler'));
    pcntl_signal(SIGUSR2, array(&$this, 'sigHandler'));

    return true;
  }

  /**
   * Cheks is daemon already running
   *
   * @return bool
   */
  private function _isDaemonRunning() {

    $oldPid = file_get_contents($this->pidFileLocation);

    if ($oldPid !== false && posix_kill(trim($oldPid),0))
    {
      $this->_logMessage('Daemon already running with PID: '.$oldPid, (self::DLOG_TO_CONSOLE | self::DLOG_ERROR));

      return true;
    }
    else
    {
      return false;
    }
  }

  /**
   * Forks process
   *
   * @return bool
   */
  private function _fork() {

    $this->_logMessage('Forking...');

    $pid = pcntl_fork();

    if ($pid == -1) {
      // 出错
      $this->_logMessage('Could not fork', self::DLOG_ERROR);

      return false;
    } elseif ($pid) {
      // 父进程
      $this->_logMessage('Killing parent');

      exit();
    } else {
      // fork的子进程
      $this->_isChildren = true;
      $this->_pid = posix_getpid();

      return true;
    }
  }

  /**
   * Sets identity of a daemon and returns result
   *
   * @return bool
   */
  private function _setIdentity() {

    if (!posix_setgid($this->groupID) || !posix_setuid($this->userID))
    {
      $this->_logMessage('Could not set identity', self::DLOG_WARNING);

      return false;
    }
    else
    {
      return true;
    }
  }

  /**
   * Signals handler
   *
   * @access public
   * @since 1.0
   * @return void
   */
  public function sigHandler($sigNo) {

    switch ($sigNo)
    {
      case SIGTERM:  // Shutdown
        $this->_logMessage('Shutdown signal');
        exit();
        break;

      case SIGCHLD:  // Halt
        $this->_logMessage('Halt signal');
        while (pcntl_waitpid(-1, $status, WNOHANG) > 0);
        break;
      case SIGUSR1:  // User-defined
        $this->_logMessage('User-defined signal 1');
        $this->_sigHandlerUser1();
        break;
      case SIGUSR2:  // User-defined
        $this->_logMessage('User-defined signal 2');
        $this->_sigHandlerUser2();
        break;
    }
  }

  /**
   * Signals handler: USR1
   * 主要用于定时清理每个进程里被缓存的域名dns解析记录
   *
   * @return void
   */
  protected function _sigHandlerUser1() {
    apc_clear_cache('user');
  }

  /**
   * Signals handler: USR2
   * 用于写入心跳包文件
   *
   * @return void
   */
  protected function _sigHandlerUser2() {

    $this->_initProcessLocation();

    file_put_contents($this->processHeartLocation, time());

    return true;
  }

  /**
   * Releases daemon pid file
   * This method is called on exit (destructor like)
   *
   * @return void
   */
  public function releaseDaemon() {

    if ($this->_isChildren && is_file($this->pidFileLocation)) {
      $this->_logMessage('Releasing daemon');

      unlink($this->pidFileLocation);
    }
  }

  /**
   * writeProcess
   * 将当前进程信息写入监控日志，另外的脚本会扫描监控日志的数据发送信号，如果没有响应则重启进程
   *
   * @return void
   */
  public function writeProcess() {

    // 初始化 proc
    $this->_initProcessLocation();

    $command = trim(implode(' ', $_SERVER['argv']));

    // 指定进程的目录
    $processDir = $this->processLocation . '/' . $this->_pid;
    $processCmdFile = $processDir . '/cmd';
    $processPwdFile = $processDir . '/pwd';

    // 所有进程所在的目录
    if (!is_dir($this->processLocation)) {
      mkdir($this->processLocation, 0777);
      chmod($processDir, 0777);
    }

    // 查询重复的进程记录
    $pDirObject = dir($this->processLocation);
    while ($pDirObject && (($pid = $pDirObject->read()) !== false)) {
      if ($pid == '.' || $pid == '..' || intval($pid) != $pid) {
        continue;
      }

      $pDir = $this->processLocation . '/' . $pid;
      $pCmdFile = $pDir . '/cmd';
      $pPwdFile = $pDir . '/pwd';
      $pHeartFile = $pDir . '/heart';

      // 根据cmd检查启动相同参数的进程
      if (is_file($pCmdFile) && trim(file_get_contents($pCmdFile)) == $command) {
        unlink($pCmdFile);
        unlink($pPwdFile);
        unlink($pHeartFile);

        // 删目录有缓存
        usleep(1000);

        rmdir($pDir);
      }
    }

    // 新进程目录
    if (!is_dir($processDir)) {
      mkdir($processDir, 0777);
      chmod($processDir, 0777);
    }

    // 写入命令参数
    file_put_contents($processCmdFile, $command);
    file_put_contents($processPwdFile, $_SERVER['PWD']);

    // 写文件有缓存
    usleep(1000);

    return true;
  }

  /**
   * _initProcessLocation
   * 初始化
   *
   * @return void
   */
  protected function _initProcessLocation() {

    $this->processLocation = ROOT_PATH . '/app/data/proc';
    $this->processHeartLocation = $this->processLocation . '/' . $this->_pid . '/heart';
  }
}