php daemon

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The daemon process (Daemon) is a process that runs in the background. a special process. It is independent of the control terminal and periodically performs some task or waits for some event to occur. Daemon is a very useful process. PHP can also implement the function of daemon process.

1. Basic concepts

Process

Each process has a parent process. When the child process exits, the parent process can get the information that the child process exits. state.

Process Group

Each process belongs to a process group. Each process group has a process group number, which is equal to the PID of the process group leader

2. Key points of daemon programming

1. Run in the background.​
​ To avoid hanging the control terminal, put Daemon into the background for execution. The method is to call fork in the process to terminate the parent process and let Daemon execute in the background in the child process. if($pid=pcntl_fork()) exit(0);//It is the parent process, end the parent process, and the child process continues
2. Leave the control terminal, log in to the session and process group
It is necessary to introduce Linux first The relationship between the process and the control terminal, the login session and the process group: the process belongs to a process group, and the process group number (GID) is the process number (PID) of the process group leader. A login session can contain multiple process groups. These process groups share a controlling terminal. This control terminal is usually the login terminal where the process was created. Controlling terminals, login sessions, and process groups are usually inherited from the parent process. Our purpose is to get rid of them and not be affected by them. The method is to call setsid() to make the process the session leader based on point 1: posix_setsid();
Description: The setsid() call fails when the process is the session leader. But the first point already ensures that the process is not the session leader. After the setsid() call is successful, the process becomes the new session group leader and new process group leader, and is separated from the original login session and process group. Due to the exclusivity of the session process to the control terminal, the process is detached from the control terminal at the same time.
3. Disable the process from reopening the control terminal
Now, the process has become the session leader without a terminal. But it can be re-applied to open a control terminal. You can prevent the process from reopening the control terminal by making the process no longer the session leader: if($pid=pcntl_fork()) exit(0);//End the first child process, the second child process Continue (the second child process is no longer the session leader)
4. Close the open file descriptor
The process inherits the open file descriptor from the parent process that created it. If it is not closed, system resources will be wasted, the file system where the process is located will not be able to be unmounted, and unpredictable errors will occur. Close them as follows:
FClose (STDIN), FClose (STDOUT), FClose (STDERR) Close Standard input Output and Error Display.
5. Change the current working directory
When a process is active, the file system where its working directory is located cannot be removed. Generally you need to change the working directory to the root directory. For the process that needs to dump the core and write the running log, change the working directory to a specific directory such as chdir("/")
6. Reset the file creation mask
The process inherits the file from the parent process that created it Create a mask. It may modify the access bits of files created by the daemon. To prevent this, clear the file creation mask: umask(0);
7. Handling the SIGCHLD signal
Handling the SIGCHLD signal is not necessary. But for some processes, especially server processes, child processes are often generated to handle requests when requests arrive. If the parent process does not wait for the child process to end, the child process will become a zombie process (zombie) and occupy system resources. If the parent process waits for the child process to end, it will increase the burden on the parent process and affect the concurrency performance of the server process. Under Linux, you can simply set the operation of the SIGCHLD signal to SIG_IGN. signal(SIGCHLD,SIG_IGN);
In this way, the kernel will not generate a zombie process when the child process ends. This is different from BSD4. Under BSD4, you must explicitly wait for the child process to end before releasing the zombie process. For questions about signals, please refer to Linux Signal description list

1. <?php  
   /** 
   *@author tengzhaorong@gmail.com 
   *@date 2013-07-25 
   * 后台脚本控制类 
   */  
   class DaemonCommand{  
      
       private $info_dir="/tmp";  
       private $pid_file="";  
       private $terminate=false; //是否中断  
       private $workers_count=0;  
       private $gc_enabled=null;  
       private $workers_max=8; //最多运行8个进程  
      
       public function __construct($is_sington=false,$user=&#39;nobody&#39;,$output="/dev/null"){  
      
               $this->is_sington=$is_sington; //是否单例运行，单例运行会在tmp目录下建立一个唯一的PID  
               $this->user=$user;//设置运行的用户 默认情况下nobody  
               $this->output=$output; //设置输出的地方  
               $this->checkPcntl();  
       }  
       //检查环境是否支持pcntl支持  
       public function checkPcntl(){  
           if ( ! function_exists(&#39;pcntl_signal_dispatch&#39;)) {  
               // PHP < 5.3 uses ticks to handle signals instead of pcntl_signal_dispatch  
               // call sighandler only every 10 ticks  
               declare(ticks = 10);  
           }  
      
           // Make sure PHP has support for pcntl  
           if ( ! function_exists(&#39;pcntl_signal&#39;)) {  
               $message = &#39;PHP does not appear to be compiled with the PCNTL extension.  This is neccesary for daemonization&#39;;  
               $this->_log($message);  
               throw new Exception($message);  
           }  
           //信号处理  
           pcntl_signal(SIGTERM, array(__CLASS__, "signalHandler"),false);  
           pcntl_signal(SIGINT, array(__CLASS__, "signalHandler"),false);  
           pcntl_signal(SIGQUIT, array(__CLASS__, "signalHandler"),false);  
      
           // Enable PHP 5.3 garbage collection  
           if (function_exists(&#39;gc_enable&#39;))  
           {  
               gc_enable();  
               $this->gc_enabled = gc_enabled();  
           }  
       }  
      
       // daemon化程序  
       public function daemonize(){  
      
           global $stdin, $stdout, $stderr;  
           global $argv;  
      
           set_time_limit(0);  
      
           // 只允许在cli下面运行  
           if (php_sapi_name() != "cli"){  
               die("only run in command line mode\n");  
           }  
      
           // 只能单例运行  
           if ($this->is_sington==true){  
      
               $this->pid_file = $this->info_dir . "/" .__CLASS__ . "_" . substr(basename($argv[0]), 0, -4) . ".pid";  
               $this->checkPidfile();  
           }  
      
           umask(0); //把文件掩码清0  
      
           if (pcntl_fork() != 0){ //是父进程，父进程退出  
               exit();  
           }  
      
           posix_setsid();//设置新会话组长，脱离终端  
      
           if (pcntl_fork() != 0){ //是第一子进程，结束第一子进程     
               exit();  
           }  
      
           chdir("/"); //改变工作目录  
      
           $this->setUser($this->user) or die("cannot change owner");  
      
           //关闭打开的文件描述符  
           fclose(STDIN);  
           fclose(STDOUT);  
           fclose(STDERR);  
      
           $stdin  = fopen($this->output, &#39;r&#39;);  
           $stdout = fopen($this->output, &#39;a&#39;);  
           $stderr = fopen($this->output, &#39;a&#39;);  
      
           if ($this->is_sington==true){  
               $this->createPidfile();  
           }  
      
       }  
       //--检测pid是否已经存在  
       public function checkPidfile(){  
      
           if (!file_exists($this->pid_file)){  
               return true;  
           }  
           $pid = file_get_contents($this->pid_file);  
           $pid = intval($pid);  
           if ($pid > 0 && posix_kill($pid, 0)){  
               $this->_log("the daemon process is already started");  
           }  
           else {  
               $this->_log("the daemon proces end abnormally, please check pidfile " . $this->pid_file);  
           }  
           exit(1);  
      
       }  
       //----创建pid  
       public function createPidfile(){  
      
           if (!is_dir($this->info_dir)){  
               mkdir($this->info_dir);  
           }  
           $fp = fopen($this->pid_file, &#39;w&#39;) or die("cannot create pid file");  
           fwrite($fp, posix_getpid());  
           fclose($fp);  
           $this->_log("create pid file " . $this->pid_file);  
       }  
      
       //设置运行的用户  
       public function setUser($name){  
      
           $result = false;  
           if (empty($name)){  
               return true;  
           }  
           $user = posix_getpwnam($name);  
           if ($user) {  
               $uid = $user[&#39;uid&#39;];  
               $gid = $user[&#39;gid&#39;];  
               $result = posix_setuid($uid);  
               posix_setgid($gid);  
           }  
           return $result;  
      
       }  
       //信号处理函数  
       public function signalHandler($signo){  
      
           switch($signo){  
      
               //用户自定义信号  
               case SIGUSR1: //busy  
               if ($this->workers_count < $this->workers_max){  
                   $pid = pcntl_fork();  
                   if ($pid > 0){  
                       $this->workers_count ++;  
                   }  
               }  
               break;  
               //子进程结束信号  
               case SIGCHLD:  
                   while(($pid=pcntl_waitpid(-1, $status, WNOHANG)) > 0){  
                       $this->workers_count --;  
                   }  
               break;  
               //中断进程  
               case SIGTERM:  
               case SIGHUP:  
               case SIGQUIT:  
      
                   $this->terminate = true;  
               break;  
               default:  
               return false;  
           }  
      
       }  
       /** 
       *开始开启进程 
       *$count 准备开启的进程数 
       */  
       public function start($count=1){  
      
           $this->_log("daemon process is running now");  
           pcntl_signal(SIGCHLD, array(__CLASS__, "signalHandler"),false); // if worker die, minus children num  
           while (true) {  
               if (function_exists(&#39;pcntl_signal_dispatch&#39;)){  
      
                   pcntl_signal_dispatch();  
               }  
      
               if ($this->terminate){  
                   break;  
               }  
               $pid=-1;  
               if($this->workers_count<$count){  
      
                   $pid=pcntl_fork();  
               }  
      
               if($pid>0){  
      
                   $this->workers_count++;  
      
               }elseif($pid==0){  
      
                   // 这个符号表示恢复系统对信号的默认处理  
                   pcntl_signal(SIGTERM, SIG_DFL);  
                   pcntl_signal(SIGCHLD, SIG_DFL);  
                   if(!empty($this->jobs)){  
                       while($this->jobs[&#39;runtime&#39;]){  
                           if(empty($this->jobs[&#39;argv&#39;])){  
                               call_user_func($this->jobs[&#39;function&#39;],$this->jobs[&#39;argv&#39;]);  
                           }else{  
                               call_user_func($this->jobs[&#39;function&#39;]);  
                           }  
                           $this->jobs[&#39;runtime&#39;]--;  
                           sleep(2);  
                       }  
                       exit();  
      
                   }  
                   return;  
      
               }else{  
      
                   sleep(2);  
               }  
      
      
           }  
      
           $this->mainQuit();  
           exit(0);  
      
       }  
      
       //整个进程退出  
       public function mainQuit(){  
      
           if (file_exists($this->pid_file)){  
               unlink($this->pid_file);  
               $this->_log("delete pid file " . $this->pid_file);  
           }  
           $this->_log("daemon process exit now");  
           posix_kill(0, SIGKILL);  
           exit(0);  
       }  
      
       // 添加工作实例，目前只支持单个job工作  
       public function setJobs($jobs=array()){  
      
           if(!isset($jobs[&#39;argv&#39;])||empty($jobs[&#39;argv&#39;])){  
      
               $jobs[&#39;argv&#39;]="";  
      
           }  
           if(!isset($jobs[&#39;runtime&#39;])||empty($jobs[&#39;runtime&#39;])){  
      
               $jobs[&#39;runtime&#39;]=1;  
      
           }  
      
           if(!isset($jobs[&#39;function&#39;])||empty($jobs[&#39;function&#39;])){  
      
               $this->log("你必须添加运行的函数！");  
           }  
      
           $this->jobs=$jobs;  
      
       }  
       //日志处理  
       private  function _log($message){  
           printf("%s\t%d\t%d\t%s\n", date("c"), posix_getpid(), posix_getppid(), $message);  
       }  
      
   }  
      
   //调用方法1  
   $daemon=new DaemonCommand(true);  
   $daemon->daemonize();  
   $daemon->start(2);//开启2个子进程工作  
   work();  
      
      
      
      
   //调用方法2  
   $daemon=new DaemonCommand(true);  
   $daemon->daemonize();  
   $daemon->addJobs(array(&#39;function&#39;=>&#39;work&#39;,&#39;argv&#39;=>&#39;&#39;,&#39;runtime&#39;=>1000));//function 要运行的函数,argv运行函数的参数，runtime运行的次数  
   $daemon->start(2);//开启2个子进程工作  
      
   //具体功能的实现  
   function work(){  
         echo "测试1";  
   }  
   ?>

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