PHPLIB-1237 Implement GridFS multi-file upload & download (#1170)

Parallel Benchmarks specs: GridFS upload & download https://github.com/mongodb/specifications/blob/ddfc8b583d49aaf8c4c19fa01255afb66b36b92e/source/benchmarking/benchmarking.rst#gridfs-upload

Single implementation using one fork for each file uploaded/downloaded.

benchmark/src/DriverBench/ParallelGridFSBench.php

@@ -0,0 +1,142 @@
+<?php
+
+namespace MongoDB\Benchmark\DriverBench;
+
+use MongoDB\Benchmark\Fixtures\Data;
+use MongoDB\Benchmark\Utils;
+use PhpBench\Attributes\BeforeMethods;
+
+use function array_map;
+use function basename;
+use function fopen;
+use function is_dir;
+use function mkdir;
+use function pcntl_fork;
+use function pcntl_waitpid;
+use function range;
+use function sprintf;
+use function stream_copy_to_stream;
+use function sys_get_temp_dir;
+use function unlink;
+
+/**
+ * For accurate results, run benchmarks on a standalone server.
+ *
+ * @see https://github.com/mongodb/specifications/blob/ddfc8b583d49aaf8c4c19fa01255afb66b36b92e/source/benchmarking/benchmarking.rst#parallel
+ */
+#[AfterMethods('cleanup')]
+final class ParallelGridFSBench
+{
+    public static function cleanup(): void
+    {
+        Utils::getDatabase()->drop();
+
+        foreach (self::getFileNames() as $file) {
+            unlink($file);
+        }
+    }
+
+    /**
+     * GridFS multi-file upload
+     *
+     * @see https://github.com/mongodb/specifications/blob/ddfc8b583d49aaf8c4c19fa01255afb66b36b92e/source/benchmarking/benchmarking.rst#gridfs-multi-file-upload
+     */
+    #[BeforeMethods('beforeUpload')]
+    public function benchUpload(): void
+    {
+        $pids = [];
+        foreach (self::getFileNames() as $file) {
+            $pid = pcntl_fork();
+            if ($pid === 0) {
+                Utils::getDatabase()->selectGridFSBucket()->uploadFromStream(basename($file), fopen($file, 'r'));
+
+                // Exit the child process
+                exit(0);
+            }
+
+            if ($pid === -1) {
+                throw new RuntimeException('Failed to fork');
+            }
+
+            // Keep the forked process id to wait for it later
+            $pids[$pid] = true;
+        }
+
+        // Wait for all child processes to finish
+        while ($pids !== []) {
+            $pid = pcntl_waitpid(-1, $status);
+            unset($pids[$pid]);
+        }
+    }
+
+    public function beforeUpload(): void
+    {
+        foreach (self::getFileNames() as $file) {
+            stream_copy_to_stream(Data::getStream(5 * 1024 * 1024), fopen($file, 'w'));
+        }
+
+        $database = Utils::getDatabase();
+        $database->drop();
+
+        $bucket = $database->selectGridFSBucket();
+        $bucket->uploadFromStream('init', Data::getStream(1));
+
+        Utils::reset();
+    }
+
+    /**
+     * GridFS multi-file download
+     *
+     * @see https://github.com/mongodb/specifications/blob/ddfc8b583d49aaf8c4c19fa01255afb66b36b92e/source/benchmarking/benchmarking.rst#gridfs-multi-file-download
+     */
+    #[BeforeMethods('beforeDownload')]
+    public function benchDownload(): void
+    {
+        $pids = [];
+        foreach (self::getFileNames() as $file) {
+            $pid = pcntl_fork();
+            if ($pid === 0) {
+                $stream = Utils::getDatabase()
+                    ->selectGridFSBucket()
+                    ->openDownloadStreamByName(basename($file));
+                stream_copy_to_stream($stream, fopen($file, 'w'));
+
+                // Exit the child process
+                exit(0);
+            }
+
+            if ($pid === -1) {
+                throw new RuntimeException('Failed to fork');
+            }
+
+            // Keep the forked process id to wait for it later
+            $pids[$pid] = true;
+        }
+
+        // Wait for all child processes to finish
+        while ($pids !== []) {
+            $pid = pcntl_waitpid(-1, $status);
+            unset($pids[$pid]);
+        }
+    }
+
+    public function beforeDownload(): void
+    {
+        // Initialize the GridFS bucket with the files
+        $this->beforeUpload();
+        $this->benchUpload();
+    }
+
+    private static function getFileNames(): array
+    {
+        $tempDir = sys_get_temp_dir() . '/mongodb-php-benchmark';
+        if (! is_dir($tempDir)) {
+            mkdir($tempDir);
+        }
+
+        return array_map(
+            static fn (int $i) => sprintf('%s/file%02d.txt', $tempDir, $i),
+            range(0, 49),
+        );
+    }
+}