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。
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_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';
}
} 
