Chris@13: <?php
Chris@13: 
Chris@13: /*
Chris@13:  * This file is part of Psy Shell.
Chris@13:  *
Chris@13:  * (c) 2012-2018 Justin Hileman
Chris@13:  *
Chris@13:  * For the full copyright and license information, please view the LICENSE
Chris@13:  * file that was distributed with this source code.
Chris@13:  */
Chris@13: 
Chris@13: namespace Psy\ExecutionLoop;
Chris@13: 
Chris@13: use Psy\Context;
Chris@13: use Psy\Exception\BreakException;
Chris@13: use Psy\Shell;
Chris@13: 
Chris@13: /**
Chris@13:  * An execution loop listener that forks the process before executing code.
Chris@13:  *
Chris@13:  * This is awesome, as the session won't die prematurely if user input includes
Chris@13:  * a fatal error, such as redeclaring a class or function.
Chris@13:  */
Chris@13: class ProcessForker extends AbstractListener
Chris@13: {
Chris@13:     private $savegame;
Chris@13:     private $up;
Chris@13: 
Chris@13:     /**
Chris@13:      * Process forker is supported if pcntl and posix extensions are available.
Chris@13:      *
Chris@13:      * @return bool
Chris@13:      */
Chris@13:     public static function isSupported()
Chris@13:     {
Chris@17:         return \function_exists('pcntl_signal') && \function_exists('posix_getpid');
Chris@13:     }
Chris@13: 
Chris@13:     /**
Chris@13:      * Forks into a master and a loop process.
Chris@13:      *
Chris@13:      * The loop process will handle the evaluation of all instructions, then
Chris@13:      * return its state via a socket upon completion.
Chris@13:      *
Chris@13:      * @param Shell $shell
Chris@13:      */
Chris@13:     public function beforeRun(Shell $shell)
Chris@13:     {
Chris@17:         list($up, $down) = \stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP);
Chris@13: 
Chris@13:         if (!$up) {
Chris@13:             throw new \RuntimeException('Unable to create socket pair');
Chris@13:         }
Chris@13: 
Chris@17:         $pid = \pcntl_fork();
Chris@13:         if ($pid < 0) {
Chris@13:             throw new \RuntimeException('Unable to start execution loop');
Chris@13:         } elseif ($pid > 0) {
Chris@13:             // This is the main thread. We'll just wait for a while.
Chris@13: 
Chris@13:             // We won't be needing this one.
Chris@17:             \fclose($up);
Chris@13: 
Chris@13:             // Wait for a return value from the loop process.
Chris@13:             $read   = [$down];
Chris@13:             $write  = null;
Chris@13:             $except = null;
Chris@16: 
Chris@16:             do {
Chris@17:                 $n = @\stream_select($read, $write, $except, null);
Chris@16: 
Chris@16:                 if ($n === 0) {
Chris@16:                     throw new \RuntimeException('Process timed out waiting for execution loop');
Chris@16:                 }
Chris@16: 
Chris@16:                 if ($n === false) {
Chris@17:                     $err = \error_get_last();
Chris@17:                     if (!isset($err['message']) || \stripos($err['message'], 'interrupted system call') === false) {
Chris@16:                         $msg = $err['message'] ?
Chris@17:                             \sprintf('Error waiting for execution loop: %s', $err['message']) :
Chris@16:                             'Error waiting for execution loop';
Chris@16:                         throw new \RuntimeException($msg);
Chris@16:                     }
Chris@16:                 }
Chris@16:             } while ($n < 1);
Chris@13: 
Chris@17:             $content = \stream_get_contents($down);
Chris@17:             \fclose($down);
Chris@13: 
Chris@13:             if ($content) {
Chris@17:                 $shell->setScopeVariables(@\unserialize($content));
Chris@13:             }
Chris@13: 
Chris@13:             throw new BreakException('Exiting main thread');
Chris@13:         }
Chris@13: 
Chris@13:         // This is the child process. It's going to do all the work.
Chris@17:         if (\function_exists('setproctitle')) {
Chris@13:             setproctitle('psysh (loop)');
Chris@13:         }
Chris@13: 
Chris@13:         // We won't be needing this one.
Chris@17:         \fclose($down);
Chris@13: 
Chris@13:         // Save this; we'll need to close it in `afterRun`
Chris@13:         $this->up = $up;
Chris@13:     }
Chris@13: 
Chris@13:     /**
Chris@13:      * Create a savegame at the start of each loop iteration.
Chris@13:      *
Chris@13:      * @param Shell $shell
Chris@13:      */
Chris@13:     public function beforeLoop(Shell $shell)
Chris@13:     {
Chris@13:         $this->createSavegame();
Chris@13:     }
Chris@13: 
Chris@13:     /**
Chris@13:      * Clean up old savegames at the end of each loop iteration.
Chris@13:      *
Chris@13:      * @param Shell $shell
Chris@13:      */
Chris@13:     public function afterLoop(Shell $shell)
Chris@13:     {
Chris@13:         // if there's an old savegame hanging around, let's kill it.
Chris@13:         if (isset($this->savegame)) {
Chris@17:             \posix_kill($this->savegame, SIGKILL);
Chris@17:             \pcntl_signal_dispatch();
Chris@13:         }
Chris@13:     }
Chris@13: 
Chris@13:     /**
Chris@13:      * After the REPL session ends, send the scope variables back up to the main
Chris@13:      * thread (if this is a child thread).
Chris@13:      *
Chris@13:      * @param Shell $shell
Chris@13:      */
Chris@13:     public function afterRun(Shell $shell)
Chris@13:     {
Chris@13:         // We're a child thread. Send the scope variables back up to the main thread.
Chris@13:         if (isset($this->up)) {
Chris@17:             \fwrite($this->up, $this->serializeReturn($shell->getScopeVariables(false)));
Chris@17:             \fclose($this->up);
Chris@13: 
Chris@17:             \posix_kill(\posix_getpid(), SIGKILL);
Chris@13:         }
Chris@13:     }
Chris@13: 
Chris@13:     /**
Chris@13:      * Create a savegame fork.
Chris@13:      *
Chris@13:      * The savegame contains the current execution state, and can be resumed in
Chris@13:      * the event that the worker dies unexpectedly (for example, by encountering
Chris@13:      * a PHP fatal error).
Chris@13:      */
Chris@13:     private function createSavegame()
Chris@13:     {
Chris@13:         // the current process will become the savegame
Chris@17:         $this->savegame = \posix_getpid();
Chris@13: 
Chris@17:         $pid = \pcntl_fork();
Chris@13:         if ($pid < 0) {
Chris@13:             throw new \RuntimeException('Unable to create savegame fork');
Chris@13:         } elseif ($pid > 0) {
Chris@13:             // we're the savegame now... let's wait and see what happens
Chris@17:             \pcntl_waitpid($pid, $status);
Chris@13: 
Chris@13:             // worker exited cleanly, let's bail
Chris@17:             if (!\pcntl_wexitstatus($status)) {
Chris@17:                 \posix_kill(\posix_getpid(), SIGKILL);
Chris@13:             }
Chris@13: 
Chris@13:             // worker didn't exit cleanly, we'll need to have another go
Chris@13:             $this->createSavegame();
Chris@13:         }
Chris@13:     }
Chris@13: 
Chris@13:     /**
Chris@13:      * Serialize all serializable return values.
Chris@13:      *
Chris@13:      * A naïve serialization will run into issues if there is a Closure or
Chris@13:      * SimpleXMLElement (among other things) in scope when exiting the execution
Chris@13:      * loop. We'll just ignore these unserializable classes, and serialize what
Chris@13:      * we can.
Chris@13:      *
Chris@13:      * @param array $return
Chris@13:      *
Chris@13:      * @return string
Chris@13:      */
Chris@13:     private function serializeReturn(array $return)
Chris@13:     {
Chris@13:         $serializable = [];
Chris@13: 
Chris@13:         foreach ($return as $key => $value) {
Chris@13:             // No need to return magic variables
Chris@13:             if (Context::isSpecialVariableName($key)) {
Chris@13:                 continue;
Chris@13:             }
Chris@13: 
Chris@13:             // Resources and Closures don't error, but they don't serialize well either.
Chris@17:             if (\is_resource($value) || $value instanceof \Closure) {
Chris@13:                 continue;
Chris@13:             }
Chris@13: 
Chris@13:             try {
Chris@17:                 @\serialize($value);
Chris@13:                 $serializable[$key] = $value;
Chris@13:             } catch (\Throwable $e) {
Chris@13:                 // we'll just ignore this one...
Chris@13:             } catch (\Exception $e) {
Chris@13:                 // and this one too...
Chris@13:                 // @todo remove this once we don't support PHP 5.x anymore :)
Chris@13:             }
Chris@13:         }
Chris@13: 
Chris@17:         return @\serialize($serializable);
Chris@13:     }
Chris@13: }