FastCGI Server / Responder over Swoole Unix domain socket

fcgi_responder.php

<?php

// based on Stone FastCGI https://github.com/StoneGroup/stone copyright MIT according to it's composer.json

class FastCGIConnection
{
    private $server;
    private $from_id;
    private $fd;

    public function __construct($server, $fd, $from_id) {
        $this->server = $server;
        $this->fd = $fd;
        $this->from_id = $from_id;
    }

    public function write($data) {
        return $this->server->send($this->fd, $data, $this->from_id);
    }
}

class FastCGIProtocol
{
    const FCGI_LISTENSOCK_FILENO = 0;
    const FCGI_VERSION_1         = 1;
    const FCGI_BEGIN_REQUEST     = 1;
    const FCGI_ABORT_REQUEST     = 2;
    const FCGI_END_REQUEST       = 3;
    const FCGI_PARAMS            = 4;
    const FCGI_STDIN             = 5;
    const FCGI_STDOUT            = 6;
    const FCGI_STDERR            = 7;
    const FCGI_DATA              = 8;
    const FCGI_GET_VALUES        = 9;
    const FCGI_RESPONDER         = 1;
    const FCGI_AUTHORIZER        = 2;
    const FCGI_FILTER            = 3;
    const FCGI_KEEP_CONNECTION   = 1;
    const FCGI_REQUEST_COMPLETE  = 0;
    const FCGI_CANT_MPX_CONN     = 1;
    const FCGI_OVERLOADED        = 2;
    const FCGI_UNKNOWN_ROLE      = 3;

    private $requests;
    private $connection;
    private $buffer;
    private $bufferLength;

    public function __construct(FastCGIConnection $connection) {
        $this->buffer = '';
        $this->bufferLength = 0;
        $this->connection = $connection;
    }

    public function readFromString($data) {
        $this->buffer .= $data;
        $this->bufferLength += strlen($data);

        while(null !== ($record = $this->readRecord())) {
            $this->processRecord($record);
        }

        return $this->requests;
    }

    public function readRecord() {
        if($this->bufferLength < 8) {
            return;
        }

        $headerData = substr($this->buffer, 0, 8);
        $headerFormat = 'Cversion/Ctype/nrequestId/ncontentLength/CpaddingLength/x';
        $record = unpack($headerFormat, $headerData);

        if($this->bufferLength - 8 < $record['contentLength'] + $record['paddingLength']) {
            return;
        }

        $record['contentData'] = substr($this->buffer, 8, $record['contentLength']);

        $recordSize = 8 + $record['contentLength'] + $record['paddingLength'];

        $this->buffer        = substr($this->buffer, $recordSize);
        $this->bufferLength -= $recordSize;

        return $record;
    }

    public function processRecord($record) {
        $requestId = $record['requestId'];
        $content = 0 === $record['contentLength'] ? null : $record['contentData'];

        if(self::FCGI_BEGIN_REQUEST === $record['type']) {
            $this->processBeginRequestRecord($requestId, $content);
        }elseif(!isset($this->requests[$requestId])) {
            throw new Exception('Invalid request id for record of type: '.$record['type']);
        }elseif(self::FCGI_PARAMS === $record['type']) {
            while(strlen($content) > 0) {
                $this->readNameValuePair($requestId, $content);
            }
        }elseif(self::FCGI_STDIN === $record['type']) {
            if(null !== $content) {
                fwrite($this->requests[$requestId]['stdin'], $content);
                $this->requests[$requestId]['rawPost'] = $content;
            }else {
                return 1;
            }
        }elseif(self::FCGI_ABORT_REQUEST === $record['type']) {
            $this->endRequest($requestId);
        }else {
            throw new Exception('Unexpected packet of type: '.$record['type']);
        }

        return 0;
    }

    private function processBeginRequestRecord($requestId, $contentData) {
        if(isset($this->requests[$requestId])) {
            throw new Exception('Unexpected FCGI_BEGIN_REQUEST record');
        }
        
        $contentFormat = 'nrole/Cflags/x5';
        $content = unpack($contentFormat, $contentData);
        $keepAlive = self::FCGI_KEEP_CONNECTION & $content['flags'];
        
        $this->requests[$requestId] = [
            'keepAlive' => $keepAlive,
            'stdin'     => fopen('php://temp', 'r+'),
            'params'    => [],
        ];
        
        if(self::FCGI_RESPONDER !== $content['role']) {
            $this->endRequest($requestId, 0, self::FCGI_UNKNOWN_ROLE);
            return;
        }
    }

    private function readNameValuePair($requestId, &$buffer) {
        $nameLength  = $this->readFieldLength($buffer);
        $valueLength = $this->readFieldLength($buffer);

        $contentFormat = (
                'a'.$nameLength.'name/'.
                'a'.$valueLength.'value/'
                );
        
        $content = unpack($contentFormat, $buffer);
        $this->requests[$requestId]['params'][$content['name']] = $content['value'];
        $buffer = substr($buffer, $nameLength + $valueLength);
    }

    private function readFieldLength(&$buffer) {
        $block  = unpack('C4', $buffer);
        $length = $block[1];
        $skip   = 1;
        
        if($length & 0x80) {
            $fullBlock = unpack('N', $buffer);
            $length    = $fullBlock[1] & 0x7FFFFFFF;
            $skip      = 4;
        }
        
        $buffer = substr($buffer, $skip);
        
        return $length;
    }

    private function beginRequest($requestId, $appStatus = 0, $protocolStatus = self::FCGI_BEGIN_REQUEST) {
        $c = pack('NC', $appStatus, $protocolStatus)
            . "\x00\x00\x00";
        
        return $this->connection->write(
                "\x01"
                . "\x01"
                . pack('nn', $req->id, strlen($c))
                . "\x00"
                . "\x00"
                . $c
                );

        $content = pack('NCx3', $appStatus, $protocolStatus);
        $this->writeRecord($requestId, self::FCGI_END_REQUEST, $content);
        $keepAlive = $this->requests[$requestId]['keepAlive'];

        unset($this->requests[$requestId]);
    }

    private function endRequest($requestId, $appStatus = 0, $protocolStatus = self::FCGI_REQUEST_COMPLETE) {
        $content = pack('NCx3', $appStatus, $protocolStatus);
        $this->writeRecord($requestId, self::FCGI_END_REQUEST, $content);
        $keepAlive = $this->requests[$requestId]['keepAlive'];

        unset($this->requests[$requestId]);
    }

    private function writeRecord($requestId, $type, $content = null) {
        $contentLength = null === $content ? 0 : strlen($content);
        $headerData = pack('CCnnxx', self::FCGI_VERSION_1, $type, $requestId, $contentLength);
        $this->connection->write($headerData);
        
        if(null !== $content) {
            $this->connection->write($content);
        }
    }

    public function sendDataToClient($requestId, $data, $header = []) {
        $dataLength = strlen($data);

        if($dataLength <= 65535) {
            $this->writeRecord($requestId, self::FCGI_STDOUT, $data);
        }else {
            $start = 0;
            $chunkSize = 8092;
            
            do {
                $this->writeRecord($requestId, self::FCGI_STDOUT, substr($data, $start, $chunkSize));
                $start += $chunkSize;
            }while($start < $dataLength);

            $this->writeRecord($requestId, self::FCGI_STDOUT);
        }

        $this->endRequest($requestId);
    }
}

$serv = new Swoole\Server("/tmp/fcgi.sock", 0, SWOOLE_PROCESS, SWOOLE_UNIX_STREAM);

$serv->set(array(
    'worker_num' => 1,
));

$serv->on('receive', function (Swoole\Server $serv, $fd, $reactor_id, $data) {
    $fastCGI = new FastCGIProtocol(new FastCGIConnection($serv, $fd, $reactor_id));
    $requestData = $fastCGI->readFromString($data);
    
    var_dump($requestData);
});

$serv->start();

The best FastCGI client is probably https://github.dev/adoy/PHP-FastCGI-Client/blob/master/src/Adoy/FastCGI/Client.php . Big plus is that it doesn't use pack/unpack so it can be easily converted to C/C++. Should be able use to replace pack/unpack in stone because it is the same packet format/protocol.

Specific functions to start at:
Stone readRecord:
https://github.com/StoneGroup/stone/blob/97b209198fd8e4f98b8d87032f005824d4114164/src/Stone/FastCGI/Protocol.php#L76
Adoy readPacket:
https://github.com/adoy/PHP-FastCGI-Client/blob/aa6611b1af00f9c5e867f6f8485b7bac071a4c1a/src/Adoy/FastCGI/Client.php#L393

Swoole uses parseFrame which is called in a loop within the Coroutine\FastCGI\Client->execute method
parseFrame: https://github.com/swoole/library/blob/1a84cb1930d88ceded926f272106c3ef66b85f1b/src/core/FastCGI/FrameParser.php#L69
execute: https://github.com/swoole/library/blob/1a84cb1930d88ceded926f272106c3ef66b85f1b/src/core/Coroutine/FastCGI/Client.php#L80-L123

Also note stdin handling
Adoy:
https://github.com/adoy/PHP-FastCGI-Client/blob/aa6611b1af00f9c5e867f6f8485b7bac071a4c1a/src/Adoy/FastCGI/Client.php#L496-L504
Swoole
https://github.com/swoole/library/blob/1a84cb1930d88ceded926f272106c3ef66b85f1b/src/core/FastCGI/Request.php#L32-L41

Swoole's example is more dynamic. By using _toString on request objects you are able to get the actual fastcgi request in one go, basically send((string) $request). Note Swoole's use of Record objects as wrappers. Example see FastCGI\Record\Stdin Stdin extends FastCGI\Record.

This allows packets to be built using $record->type and $record->getContent()