PHP backend socket service long link, multiple concurrent development notes_PHP tutorial

[php]
       //保证子进程上限  
        if($this->_maxFork >0  && $this->_children > $this->_maxFork) 
        { 
            Yii::log("_children > ".$this->_maxFork,CLogger::LEVEL_WARNING,__METHOD__); 
            $this->handler(SIGCHLD); 
               usleep(200); 
            continue; 
        } 
 
 
/**
* Monitoring signal
* @param object socket $clientt
* @return boolean
​*/ 
public function handler($signo) { 
     
    Yii::log("handler {$signo} ",CLogger::LEVEL_INFO, __METHOD__); 
     
    switch(intval($signo)) { 
        case SIGCLD: 
        case SIGCHLD: 
             
            Yii::log("SIGCHLD sub proccess   ",CLogger::LEVEL_TRACE, __METHOD__); 
            //正常退出  
            //declare = 1, that means one signal may be correspond multi-process die   
            while( ($pid = pcntl_wait($status, WNOHANG|WUNTRACED)) > 0 ) { 
                if (FALSE === pcntl_wifexited($status)) { 
                    Yii::log("sub proccess {$pid} exited unormally with code {$status}",CLogger::LEVEL_WARNING, __METHOD__); 
                } else { 
                    Yii::log("sub proccess {$pid} exited normally",CLogger::LEVEL_INFO, __METHOD__); 
                } 
                $this->_children--; 
            } 
            break; 
        case SIGINT: 
        case SIGQUIT: 
        case SIGHUP: 
            //异常退出  
           $this->_cleanup(); 
            exit(0); 
            break; 
        default: 
            break; 
    } 
} 

            //保证子进程上限
            if($this->_maxFork >0  && $this->_children > $this->_maxFork)
            {
                Yii::log("_children > ".$this->_maxFork,CLogger::LEVEL_WARNING,__METHOD__);
                $this->handler(SIGCHLD);
//                 usleep(200);
                continue;
            }

    /**
* Monitoring signal
* @param object socket $clientt
* @return boolean
​​*/
    public function handler($signo) {
       
        Yii::log("handler {$signo} ",CLogger::LEVEL_INFO, __METHOD__);
       
        switch(intval($signo)) {
            case SIGCLD:
            case SIGCHLD:
               
                Yii::log("SIGCHLD sub proccess   ",CLogger::LEVEL_TRACE, __METHOD__);
                //正常退出
                //declare = 1, that means one signal may be correspond multi-process die
                while( ($pid = pcntl_wait($status, WNOHANG|WUNTRACED)) > 0 ) {
                    if (FALSE === pcntl_wifexited($status)) {
                        Yii::log("sub proccess {$pid} exited unormally with code {$status}",CLogger::LEVEL_WARNING, __METHOD__);
                    } else {
                        Yii::log("sub proccess {$pid} exited normally",CLogger::LEVEL_INFO, __METHOD__);
                    }
                    $this->_children--;
                }
                break;
            case SIGINT:
            case SIGQUIT:
            case SIGHUP:
                //异常退出
               $this->_cleanup();
                exit(0);
                break;
            default:
                break;
        }
    }

【多进程方式注意点】

变量共享问题
因为是进程，可以理解成主进程的一个拷贝，执行是从调用 pcntl_fork() 后各主、子进程后自往后运行，避免子进程层层嵌套，一般子进程执行完后是用exit(0)来退出。 子进程如果执行过程中崩溃不会影响到主进程，也不能和主进程共享变量。

信号和select 冲突问题
pcntl_signal 注册信号后会和 stream_select 有冲突
PHP Error[2]: stream_select(): unable to select [4]: 被中断的系统调用 (max_fd=10)
目前没找到解决方法，未采用 pcntl_signal  进行监控。

进程回收
子进程通过exit退出后，会变成僵尸进程，需要通过 pcntl_wait 来进行回收。
centos 测试中发现最大的进程上限是3.2万，通过设置子进程总数，大于设定值再调用 pcntl_wait 来进行回收

socket读写注意
多进程情况下，会出现对同个socket句柄，有多个进程同时在读的问题。
解决方法是读操作在主进程里，读出所有数据后，抛给子进程进行执行。

Note on file operations
In the case of multiple processes, the filesize function may not be fetched or the size of the fetched files remains unchanged
This is solved by directly calling the system function under Linux.

$file_size = @filesize($logFile);
               //Solve the problem of not being able to get the file size under concurrent conditions
If(0 == $file_size ||$this->_prevFileSize == $file_size )
                                                                               $file_size = @exec('/usr/bin/stat -c %s '. escapeshellarg($logFile));
                clearstatcache();                                                                        }

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