OrderedStreamingForkController.php

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<?php
namespace MediaWiki\Maintenance;
 
class OrderedStreamingForkController extends ForkController {
    protected $workCallback;
    protected $input;
    protected $output;
    protected $nextOutputId;
    protected $delayedOutputData = [];
 
    public function __construct( $numProcs, $workCallback, $input, $output ) {
        parent::__construct( $numProcs );
        $this->workCallback = $workCallback;
        $this->input = $input;
        $this->output = $output;
    }
 
    public function start() {
        if ( $this->procsToStart > 0 ) {
            $status = parent::start();
            if ( $status === 'child' ) {
                $this->consume();
            }
        } else {
            $status = 'parent';
            $this->consumeNoFork();
        }
        return $status;
    }
 
    protected function forkWorkers( $numProcs ) {
        $this->prepareEnvironment();
 
        $childSockets = [];
        // Create the child processes
        for ( $i = 0; $i < $numProcs; $i++ ) {
            $sockets = stream_socket_pair( STREAM_PF_UNIX, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP );
            // Do the fork
            $pid = pcntl_fork();
            if ( $pid === -1 ) {
                echo "Error creating child processes\n";
                exit( 1 );
            }
 
            if ( !$pid ) {
                $this->initChild();
                $this->childNumber = $i;
                $this->input = $sockets[0];
                $this->output = $sockets[0];
                fclose( $sockets[1] );
                return 'child';
            } else {
                // This is the parent process
                $this->children[$pid] = true;
                fclose( $sockets[0] );
                $childSockets[] = $sockets[1];
            }
        }
        $this->feedChildren( $childSockets );
        foreach ( $childSockets as $socket ) {
            fclose( $socket );
        }
        return 'parent';
    }
 
    protected function consume() {
        while ( !feof( $this->input ) ) {
            $line = trim( fgets( $this->input ) );
            if ( $line ) {
                [ $id, $data ] = json_decode( $line );
                $result = ( $this->workCallback )( $data );
                fwrite( $this->output, json_encode( [ $id, $result ] ) . "\n" );
            }
        }
    }
 
    protected function consumeNoFork() {
        while ( !feof( $this->input ) ) {
            $data = fgets( $this->input );
            if ( substr( $data, -1 ) === "\n" ) {
                // Strip any final new line used to delimit lines of input.
                // The last line of input might not have it, though.
                $data = substr( $data, 0, -1 );
            }
            if ( $data === '' ) {
                continue;
            }
            $result = ( $this->workCallback )( $data );
            fwrite( $this->output, "$result\n" );
        }
    }
 
    protected function feedChildren( array $sockets ) {
        $used = [];
        $id = 0;
        $this->nextOutputId = 0;
 
        while ( !feof( $this->input ) ) {
            $data = fgets( $this->input );
            if ( $used ) {
                do {
                    $this->updateAvailableSockets( $sockets, $used, $sockets ? 0 : 5 );
                } while ( !$sockets );
            }
            if ( substr( $data, -1 ) === "\n" ) {
                // Strip any final new line used to delimit lines of input.
                // The last line of input might not have it, though.
                $data = substr( $data, 0, -1 );
            }
            if ( $data === '' ) {
                continue;
            }
            $socket = array_pop( $sockets );
            fwrite( $socket, json_encode( [ $id++, $data ] ) . "\n" );
            $used[] = $socket;
        }
        while ( $used ) {
            $this->updateAvailableSockets( $sockets, $used, 5 );
        }
    }
 
    protected function updateAvailableSockets( &$sockets, &$used, $timeout ) {
        $read = $used;
        $write = $except = [];
        stream_select( $read, $write, $except, $timeout );
        foreach ( $read as $socket ) {
            $line = fgets( $socket );
            [ $id, $data ] = json_decode( trim( $line ) );
            $this->receive( (int)$id, $data );
            $sockets[] = $socket;
            $idx = array_search( $socket, $used );
            unset( $used[$idx] );
        }
    }
 
    protected function receive( $id, $data ) {
        if ( $id !== $this->nextOutputId ) {
            $this->delayedOutputData[$id] = $data;
            return;
        }
        fwrite( $this->output, $data . "\n" );
        $this->nextOutputId = $id + 1;
        while ( isset( $this->delayedOutputData[$this->nextOutputId] ) ) {
            fwrite( $this->output, $this->delayedOutputData[$this->nextOutputId] . "\n" );
            unset( $this->delayedOutputData[$this->nextOutputId] );
            $this->nextOutputId++;
        }
    }
}
 
class_alias( OrderedStreamingForkController::class, 'OrderedStreamingForkController' );