Drop Fork along with Process and Strand interfaces

Forking is just too dangerous for virtually no gain over Process. Context now extends Sync\Channel.

lib/Context.php

@@ -4,7 +4,7 @@ namespace Amp\Parallel;
 
 use Amp\Promise;
 
-interface Context {
+interface Context extends Sync\Channel {
     /**
      * @return bool
      */

lib/Forking/Fork.php

@@ -1,354 +0,0 @@
-<?php
-
-namespace Amp\Parallel\Forking;
-
-use Amp\Coroutine;
-use Amp\Loop;
-use Amp\Parallel\ContextException;
-use Amp\Parallel\Process;
-use Amp\Parallel\StatusError;
-use Amp\Parallel\Strand;
-use Amp\Parallel\Sync\Channel;
-use Amp\Parallel\Sync\ChannelException;
-use Amp\Parallel\Sync\ChannelledSocket;
-use Amp\Parallel\Sync\ExitFailure;
-use Amp\Parallel\Sync\ExitResult;
-use Amp\Parallel\Sync\ExitSuccess;
-use Amp\Parallel\Sync\SerializationException;
-use Amp\Parallel\SynchronizationError;
-use Amp\Promise;
-use function Amp\call;
-
-/**
- * Implements a UNIX-compatible context using forked processes.
- */
-class Fork implements Process, Strand {
-    /** @var \Amp\Parallel\Sync\ChannelledSocket A channel for communicating with the child. */
-    private $channel;
-
-    /** @var int */
-    private $pid = 0;
-
-    /** @var callable */
-    private $function;
-
-    /** @var mixed[] */
-    private $args;
-
-    /** @var int */
-    private $oid = 0;
-
-    /**
-     * Checks if forking is enabled.
-     *
-     * @return bool True if forking is enabled, otherwise false.
-     */
-    public static function supported(): bool {
-        return \extension_loaded('pcntl');
-    }
-
-    /**
-     * Spawns a new forked process and runs it.
-     *
-     * @param callable $function A callable to invoke in the process.
-     *
-     * @return \Amp\Parallel\Forking\Fork The process object that was spawned.
-     */
-    public static function spawn(callable $function, ...$args): self {
-        $fork = new self($function, ...$args);
-        $fork->start();
-        return $fork;
-    }
-
-    public function __construct(callable $function, ...$args) {
-        if (!self::supported()) {
-            throw new \Error("The pcntl extension is required to create forks.");
-        }
-
-        $this->function = $function;
-        $this->args = $args;
-    }
-
-    public function __clone() {
-        $this->pid = 0;
-        $this->oid = 0;
-        $this->channel = null;
-    }
-
-    public function __destruct() {
-        if (0 !== $this->pid && \posix_getpid() === $this->oid) { // Only kill in owner process.
-            $this->kill(); // Will only terminate if the process is still running.
-        }
-    }
-
-    /**
-     * Checks if the context is running.
-     *
-     * @return bool True if the context is running, otherwise false.
-     */
-    public function isRunning(): bool {
-        return 0 !== $this->pid && false !== \posix_getpgid($this->pid);
-    }
-
-    /**
-     * Gets the forked process's process ID.
-     *
-     * @return int The process ID.
-     */
-    public function getPid(): int {
-        return $this->pid;
-    }
-
-    /**
-     * Gets the fork's scheduling priority as a percentage.
-     *
-     * The priority is a float between 0 and 1 that indicates the relative priority for the forked process, where 0 is
-     * very low priority, 1 is very high priority, and 0.5 is considered a "normal" priority. The value is based on the
-     * forked process's "nice" value. The priority affects the operating system's scheduling of processes. How much the
-     * priority actually affects the amount of CPU time the process gets is ultimately system-specific.
-     *
-     * @return float A priority value between 0 and 1.
-     *
-     * @throws ContextException If the operation failed.
-     *
-     * @see Fork::setPriority()
-     * @see http://linux.die.net/man/2/getpriority
-     */
-    public function getPriority(): float {
-        if (($nice = \pcntl_getpriority($this->pid)) === false) {
-            throw new ContextException('Failed to get the fork\'s priority.');
-        }
-
-        return (19 - $nice) / 39;
-    }
-
-    /**
-     * Sets the fork's scheduling priority as a percentage.
-     *
-     * Note that on many systems, only the superuser can increase the priority of a process.
-     *
-     * @param float $priority A priority value between 0 and 1.
-     *
-     * @throws \Error If the given priority is an invalid value.
-     * @throws ContextException If the operation failed.
-     *
-     * @see Fork::getPriority()
-     */
-    public function setPriority(float $priority) {
-        if ($priority < 0 || $priority > 1) {
-            throw new \Error('Priority value must be between 0.0 and 1.0.');
-        }
-
-        $nice = (int) \round(19 - ($priority * 39));
-
-        if (!\pcntl_setpriority($nice, $this->pid, \PRIO_PROCESS)) {
-            throw new ContextException('Failed to set the fork\'s priority.');
-        }
-    }
-
-    /**
-     * Starts the context execution.
-     *
-     * @throws \Amp\Parallel\ContextException If forking fails.
-     */
-    public function start() {
-        if (0 !== $this->oid) {
-            throw new StatusError('The context has already been started.');
-        }
-
-        $sockets = @\stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP);
-
-        if ($sockets === false) {
-            $message = "Failed to create socket pair";
-            if ($error = \error_get_last()) {
-                $message .= \sprintf(" Errno: %d; %s", $error["type"], $error["message"]);
-            }
-            throw new ContextException($message);
-        }
-
-        list($parent, $child) = $sockets;
-
-        switch ($pid = \pcntl_fork()) {
-            case -1: // Failure
-                throw new ContextException('Could not fork process!');
-
-            case 0: // Child
-                // @codeCoverageIgnoreStart
-                \fclose($child);
-
-                Loop::set((new Loop\DriverFactory)->create()); // Replace loop instance inherited from parent.
-                Loop::run(function () use ($parent) {
-                    return $this->execute(new ChannelledSocket($parent, $parent));
-                });
-
-                exit(0);
-                // @codeCoverageIgnoreEnd
-            default: // Parent
-                $this->pid = $pid;
-                $this->oid = \posix_getpid();
-                $this->channel = new ChannelledSocket($child, $child);
-                \fclose($parent);
-        }
-    }
-
-    /**
-     * @coroutine
-     *
-     * This method is run only on the child.
-     *
-     * @param \Amp\Parallel\Sync\Channel $channel
-     *
-     * @return \Generator
-     *
-     * @codeCoverageIgnore Only executed in the child.
-     */
-    private function execute(Channel $channel): \Generator {
-        try {
-            if ($this->function instanceof \Closure) {
-                $result = call($this->function->bindTo($channel, null), ...$this->args);
-            } else {
-                $result = call($this->function, ...$this->args);
-            }
-
-            $result = new ExitSuccess(yield $result);
-        } catch (\Throwable $exception) {
-            $result = new ExitFailure($exception);
-        }
-
-        // Attempt to return the result.
-        try {
-            try {
-                yield $channel->send($result);
-            } catch (SerializationException $exception) {
-                // Serializing the result failed. Send the reason why.
-                yield $channel->send(new ExitFailure($exception));
-            }
-        } catch (ChannelException $exception) {
-            // The result was not sendable! The parent context must have died or killed the context.
-        }
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function kill() {
-        if ($this->isRunning()) {
-            // Forcefully kill the process using SIGKILL.
-            \posix_kill($this->pid, \SIGKILL);
-        }
-
-        if ($this->channel !== null) {
-            $this->channel->close();
-        }
-
-        // "Detach" from the process and let it die asynchronously.
-        $this->pid = 0;
-        $this->channel = null;
-    }
-
-    /**
-     * @param int $signo
-     *
-     * @throws \Amp\Parallel\StatusError
-     */
-    public function signal(int $signo) {
-        if (0 === $this->pid) {
-            throw new StatusError('The fork has not been started or has already finished.');
-        }
-
-        \posix_kill($this->pid, $signo);
-    }
-
-    /**
-     * Gets a promise that resolves when the context ends and joins with the
-     * parent context.
-     *
-     * @return \Amp\Promise<int>
-     *
-     * @throws \Amp\Parallel\StatusError          Thrown if the context has not been started.
-     * @throws \Amp\Parallel\SynchronizationError Thrown if an exit status object is not received.
-     */
-    public function join(): Promise {
-        if (null === $this->channel) {
-            throw new StatusError('The fork has not been started or has already finished.');
-        }
-
-        return new Coroutine($this->doJoin());
-    }
-
-    /**
-     * @coroutine
-     *
-     * @return \Generator
-     *
-     * @throws \Amp\Parallel\SynchronizationError
-     */
-    private function doJoin(): \Generator {
-        try {
-            $response = yield $this->channel->receive();
-
-            if (!$response instanceof ExitResult) {
-                throw new SynchronizationError(\sprintf(
-                    'Did not receive an exit result from fork. Instead received data of type %s',
-                    \is_object($response) ? \get_class($response) : \gettype($response)
-                ));
-            }
-        } catch (ChannelException $e) {
-            throw new ContextException("The context stopped responding, potentially due to a fatal error or calling exit", 0, $e);
-        } finally {
-            $this->kill();
-        }
-
-        return $response->getResult();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function receive(): Promise {
-        if (null === $this->channel) {
-            throw new StatusError('The process has not been started.');
-        }
-
-        return new Coroutine($this->doReceive());
-    }
-
-    private function doReceive() {
-        try {
-            $data = yield $this->channel->receive();
-        } catch (ChannelException $e) {
-            throw new ContextException("The context stopped responding, potentially due to a fatal error or calling exit", 0, $e);
-        }
-
-        if ($data instanceof ExitResult) {
-            $data = $data->getResult();
-            throw new SynchronizationError(\sprintf(
-                'Forked process unexpectedly exited with result of type: %s',
-                \is_object($data) ? \get_class($data) : \gettype($data)
-            ));
-        }
-
-        return $data;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function send($data): Promise {
-        if (null === $this->channel) {
-            throw new StatusError('The fork has not been started or has already finished.');
-        }
-
-        if ($data instanceof ExitResult) {
-            throw new \Error('Cannot send exit result objects.');
-        }
-
-        return call(function () use ($data) {
-            try {
-                yield $this->channel->send($data);
-            } catch (ChannelException $e) {
-                throw new ContextException("The context went away, potentially due to a fatal error or calling exit", 0, $e);
-            }
-        });
-    }
-}

lib/Process.php

@@ -1,17 +0,0 @@
-<?php
-
-namespace Amp\Parallel;
-
-interface Process extends Context {
-    /**
-     * @return int PID of process.
-     */
-    public function getPid(): int;
-
-    /**
-     * @param int $signo
-     *
-     * @throws \Amp\Parallel\StatusError
-     */
-    public function signal(int $signo);
-}

lib/Process/ChannelledProcess.php

@@ -4,10 +4,9 @@ namespace Amp\Parallel\Process;
 
 use Amp\ByteStream;
 use Amp\Coroutine;
+use Amp\Parallel\Context;
 use Amp\Parallel\ContextException;
-use Amp\Parallel\Process as ProcessContext;
 use Amp\Parallel\StatusError;
-use Amp\Parallel\Strand;
 use Amp\Parallel\Sync\ChannelException;
 use Amp\Parallel\Sync\ChannelledStream;
 use Amp\Parallel\Sync\ExitResult;
@@ -17,7 +16,7 @@ use Amp\Promise;
 use function Amp\asyncCall;
 use function Amp\call;
 
-class ChannelledProcess implements ProcessContext, Strand {
+class ChannelledProcess implements Context {
     /** @var \Amp\Process\Process */
     private $process;
 
@@ -187,18 +186,4 @@ class ChannelledProcess implements ProcessContext, Strand {
     public function kill() {
         $this->process->kill();
     }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getPid(): int {
-        return $this->process->getPid();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function signal(int $signo) {
-        $this->process->signal($signo);
-    }
 }

lib/Strand.php

@@ -1,6 +0,0 @@
-<?php
-
-namespace Amp\Parallel;
-
-interface Strand extends Context, Sync\Channel {
-}

lib/Worker/AbstractWorker.php

@@ -4,16 +4,16 @@ namespace Amp\Parallel\Worker;
 
 use Amp\Coroutine;
 use Amp\Deferred;
+use Amp\Parallel\Context;
 use Amp\Parallel\ContextException;
 use Amp\Parallel\StatusError;
-use Amp\Parallel\Strand;
 use Amp\Promise;
 
 /**
  * Base class for most common types of task workers.
  */
 abstract class AbstractWorker implements Worker {
-    /** @var \Amp\Parallel\Strand */
+    /** @var \Amp\Parallel\Context */
     private $context;
 
     /** @var bool */
@@ -26,10 +26,10 @@ abstract class AbstractWorker implements Worker {
     private $onResolve;
 
     /**
-     * @param \Amp\Parallel\Strand $strand
+     * @param \Amp\Parallel\Context $context
      */
-    public function __construct(Strand $strand) {
+    public function __construct(Context $context) {
-        $this->context = $strand;
+        $this->context = $context;
 
         $this->onResolve = function ($exception, $data) {
             if ($exception) {

test/Forking/ForkTest.php

@@ -1,29 +0,0 @@
-<?php
-
-namespace Amp\Parallel\Test\Forking;
-
-use Amp\Loop;
-use Amp\Parallel\Forking\Fork;
-use Amp\Parallel\Test\AbstractContextTest;
-
-/**
- * @group forking
- * @requires extension pcntl
- */
-class ForkTest extends AbstractContextTest {
-    public function createContext(callable $function) {
-        return new Fork($function);
-    }
-
-    public function testSpawnStartsFork() {
-        Loop::run(function () {
-            $fork = Fork::spawn(function () {
-                usleep(100);
-            });
-
-            $this->assertTrue($fork->isRunning());
-
-            return yield $fork->join();
-        });
-    }
-}

test/Sync/PosixSemaphoreTest.php

@@ -52,43 +52,4 @@ class PosixSemaphoreTest extends AbstractSemaphoreTest {
 
         $this->assertTrue($this->semaphore->isFreed());
     }
-
-    /**
-     * @requires extension pcntl
-     */
-    public function testAcquireInMultipleForks() {
-        Loop::run(function () {
-            $this->semaphore = $this->createSemaphore(1);
-
-            $fork1 = new Fork(function (Semaphore $semaphore) {
-                $lock = yield $semaphore->acquire();
-
-                usleep(100000);
-
-                $lock->release();
-
-                return 0;
-            }, $this->semaphore);
-
-            $fork2 = new Fork(function (Semaphore $semaphore) {
-                $lock = yield $semaphore->acquire();
-
-                usleep(100000);
-
-                $lock->release();
-
-                return 1;
-            }, $this->semaphore);
-
-            $start = microtime(true);
-
-            $fork1->start();
-            $fork2->start();
-
-            yield $fork1->join();
-            yield $fork2->join();
-
-            $this->assertGreaterThan(0.1, microtime(true) - $start);
-        });
-    }
 }