root@d856fd02d2fe:~# ps aux -L
USER  PID LWP %CPU NLWP %MEM VSZ RSS TTY  STAT START TIME COMMAND
root   1  1 0.0 1 0.0 4504 692 ?  Ss 13:10 0:00 /bin/sh /usr/local/php/bin/php-fpm start
root   7  7 0.0 1 0.4 176076 19304 ?  Ss 13:10 0:00 php-fpm: master process (/usr/local/php/etc/php-fpm.conf)
www-data  8  8 0.0 1 0.2 176076 8132 ?  S 13:10 0:00 php-fpm: pool www
www-data  9  9 0.0 1 0.2 176076 8132 ?  S 13:10 0:00 php-fpm: pool www
root  10 10 0.0 1 0.0 18376 3476 ?  Ss 14:11 0:00 bash
root  66 66 0.0 1 0.0 34420 2920 ?  R+ 15:13 0:00 ps aux -L

<?php
/**
 * PHP 只支持多進程不支持多線程。
 *
 * PHP-FPM 在進程池中運行多個子進程并發(fā)處理所有連接，
 * 同一個子進程可先后處理多個連接請求，但同一時間
 * 只能處理一個連接請求，未處理連接請求將進入隊列等待處理
 *
 */

class SimulatedThread
{
 //模擬線程
 private $thread;

 //主機名
 private $host = 'tcp://172.17.0.5';

 //端口號
 private $port = 80;

 public function __construct()
 {
  //采用當前時間給線程編號
  $this->thread = microtime(true);
 }

 /**
  * 通過socket發(fā)送一個新的HTTP連接請求到本機，
  * 此時當前模擬線程既是服務端又是模擬客戶端
  *
  * 當前(程序)子進程sleep(1)后會延遲1s才繼續(xù)執(zhí)行，但其持有的連接是繼續(xù)有效的，
  * 不能處理新的連接請求，故這種做法會降低進程池處理并發(fā)連接請求的能力，
  * 類似延遲處理還有time_nanosleep()、time_sleep_until()、usleep()。
  * 而且sleep(1)這種做法并不安全，nginx依然可能出現如下錯誤：
  * “epoll_wait() reported that client prematurely closed connection,
  * so upstream connection is closed too while connecting to upstream”
  *
  * @return void
  */
 public function simulate()
 {
  $run = $_GET['run'] ?? 0;
  if ($run++ < 9) {//最多模擬10個線程
   $fp = fsockopen($this->host, $this->port);
   fputs($fp, "GET {$_SERVER['PHP_SELF']}?run={$run}\r\n\r\n");
   sleep(1);//usleep(500)
   fclose($fp);
  }

  $this->log();
 }

 /**
  * 日志記錄當前模擬線程運行時間
  *
  * @return void
  */
 private function log()
 {
  $fp = fopen('simulated.thread', 'a');
  fputs($fp, "Log thread {$this->thread} at " . microtime(true) . "(s)\r\n");

  fclose($fp);
 }
}

$thread = new SimulatedThread();
$thread->simulate();
echo "Started to simulate threads...";

Log thread 1508054181.4236 at 1508054182.4244(s)
Log thread 1508054181.4248 at 1508054182.4254(s)
Log thread 1508054181.426 at 1508054182.428(s)
Log thread 1508054181.6095 at 1508054182.6104(s)
Log thread 1508054182.4254 at 1508054183.4262(s)
Log thread 1508054183.4272 at 1508054183.4272(s)
Log thread 1508054182.4269 at 1508054183.4275(s)
Log thread 1508054182.4289 at 1508054183.43(s)
Log thread 1508054182.6085 at 1508054183.6091(s)
Log thread 1508054182.611 at 1508054183.6118(s)

Log thread 1508058075.042 at 1508058076.0428(s)
Log thread 1508058075.0432 at 1508058076.0439(s)
Log thread 1508058075.0443 at 1508058076.045(s)
Log thread 1508058075.6623 at 1508058076.6634(s)
Log thread 1508058076.0447 at 1508058077.0455(s)
Log thread 1508058076.046 at 1508058077.0466(s)
Log thread 1508058077.0465 at 1508058077.0466(s)
Log thread 1508058076.0469 at 1508058077.0474(s)
Log thread 1508058076.6647 at 1508058077.6659(s)
Log thread 1508058076.6664 at 1508058077.6671(s)

Log thread 1508061169.7956 at 1508061170.7963(s)
Log thread 1508061169.7966 at 1508061170.7976(s)
Log thread 1508061169.7978 at 1508061170.7988(s)
Log thread 1508061170.2896 at 1508061171.2901(s)
Log thread 1508061170.7972 at 1508061171.7978(s)
Log thread 1508061171.7984 at 1508061171.7985(s)
Log thread 1508061170.7982 at 1508061171.7986(s)
Log thread 1508061170.7994 at 1508061171.8(s)
Log thread 1508061171.2907 at 1508061172.2912(s)
Log thread 1508061171.2912 at 1508061172.2915(s)

Log thread 1508059270.3195 at 1508059270.3206(s)
Log thread 1508059270.3208 at 1508059270.3219(s)
Log thread 1508059270.322 at 1508059270.323(s)
Log thread 1508059270.323 at 1508059270.324(s)
Log thread 1508059270.3244 at 1508059270.3261(s)
Log thread 1508059270.3256 at 1508059270.3271(s)
Log thread 1508059270.3275 at 1508059270.3286(s)
Log thread 1508059270.3288 at 1508059270.3299(s)
Log thread 1508059270.3299 at 1508059270.331(s)
Log thread 1508059270.3313 at 1508059270.3314(s)