TeX to PDF async server (aerys, amphp)

composer.json

{
    "require": {
        "amphp/amp": "^2.0",
        "amphp/aerys": "^0.7.4",
        "amphp/process": "^0.3.1"
    }
}

Dockerfile

FROM php:7.2.2-cli-stretch

# tex
RUN apt-get update && apt-get install -y texlive-full\
    biber\
    tar\
    libarchive-tools

# composer
RUN curl -sS https://getcomposer.org/installer | php -- --filename=composer --install-dir=/bin

EXPOSE 1337

# CMD & other stuff is up to you

pdfserver.php

<?php
/**
 * (c) Artem Ostretsov <artem@ostretsov.ru>
 * Created at 15.02.18 15:23.
 */

use Aerys\{Bootable, Host, Request, Response, function router};

date_default_timezone_set('Europe/Moscow');

$router = router()
    ->route('POST', '/', function(Request $request, Response $response) {
        // reset on timeout
        $timeout = (int) getenv('TIMEOUT') ?: 3 * 60; // in seconds
        $request->getLocalVar('logger')->debug($request->getLocalVar('request_microtime').': request timeout: '.$timeout);
        Amp\Loop::delay($timeout * 1000, function () use ($request, $response) {
            if (Response::NONE == $response->state()) {
                $response->setStatus(408);
                $response->end();
                $request->getLocalVar('logger')->debug($request->getLocalVar('request_microtime').': processing was stopped on timeout');
            }
        });

        // parse POST body
        parse_str(yield $request->getBody(), $params);

        // param validation
        $TeXFile = $params['tex_file'] ?? false;
        if (!$TeXFile) {
            $response->setStatus(400);
            $message = '"tex_file" parameter is required!';
            $response->end($message);
            $request->getLocalVar('logger')->warning($request->getLocalVar('request_microtime').': '.$message);

            return;
        }

        if (!preg_match('/\.tex$/', $TeXFile)) {
            $response->setStatus(400);
            $message = '"tex_file" parameter must be a filepath with "tex" extension!';
            $response->end($message);
            $request->getLocalVar('logger')->warning($request->getLocalVar('request_microtime').': '.$message);

            return;
        }

        if (!file_exists($TeXFile)) {
            $response->setStatus(404);
            $message = sprintf('File "%s" not found!', $TeXFile);
            $response->end($message);
            $request->getLocalVar('logger')->warning($request->getLocalVar('request_microtime').': '.$message);

            return;
        }

        $PDFFile = str_replace('.tex', '.pdf', $TeXFile);
        if (file_exists($PDFFile)) {
            $request->getLocalVar('logger')->debug($request->getLocalVar('request_microtime').': unlink '.$PDFFile);
            unlink($PDFFile);
        }

        // generate PDF
        $attempts = 2;  // sometimes it's required to execute parsing twice to generate PDF
        while ($attempts > 0) {
            // timeout for abandoned processes
            $command = sprintf('timeout %ds /usr/bin/pdflatex -interaction=batchmode -output-directory=%s %s', $timeout, dirname($TeXFile), $TeXFile);
            $request->getLocalVar('logger')->debug($request->getLocalVar('request_microtime').': '.$command);
            $process = new Amp\Process\Process($command, dirname($TeXFile));
            $process->start();
            yield new Amp\ByteStream\Message($process->getStdout());

            --$attempts;
        }

        if (Response::NONE == $response->state()) {
            // change PDF and other files permissions
            $response->write(''); // to prevent resetting on timeout

            $command = sprintf('chown `stat -c "%%u:%%g" %s` %s/%s*', $TeXFile, dirname($TeXFile), pathinfo($TeXFile, PATHINFO_FILENAME));
            $request->getLocalVar('logger')->debug($request->getLocalVar('request_microtime').': '.$command);
            $process = new Amp\Process\Process($command);
            $process->start();
            yield new Amp\ByteStream\Message($process->getStdout());

            $response->end();
        }

        $request->getLocalVar('logger')->debug($request->getLocalVar('request_microtime').': request is processed');
    });

return (new Host)
    ->expose('*', 1337)
    ->use(new class implements Bootable {
        private $logger;

        function boot(Aerys\Server $server, Psr\Log\LoggerInterface $logger) {
            $this->logger = $logger;
        }

        function __invoke(Aerys\Request $request, Aerys\Response $response) {
            $requestMicrotime = microtime(true) * 10000;
            $this->logger->debug($requestMicrotime.': request is recieved');
            $request->setLocalVar('logger', $this->logger);
            $request->setLocalVar('request_microtime', $requestMicrotime);
        }
    })
    ->use($router);