Limit number of concurrent preview generations

Signed-off-by: Bowen Ding <dbw9580@live.com>
nextcloud · Nov 4, 2020 · 18eeb79 · 18eeb79
1 parent b65d9eb
commit 18eeb79
Show file tree

Hide file tree

Showing 2 changed files with 48 additions and 1 deletion.
diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
@@ -45,6 +45,9 @@
 
 class Generator {
 
+	public const SEMAPHORE_ID_ALL = 0x0a11;
+	public const SEMAPHORE_ID_NEW = 0x07ea;
+
 	/** @var IPreview */
 	private $previewManager;
 	/** @var IConfig */
@@ -204,6 +207,34 @@ public function generatePreviews(File $file, array $specifications, $mimeType =
 		return $preview;
 	}
 
+	/**
+	 * @param int $semId
+	 * @param int $concurrency
+	 * @return bool|resource the semaphore on success or false on failure
+	 */
+	public static function guardWithSemaphore(int $semId, int $concurrency) {
+		if (extension_loaded('sysvsem')) {
+			$sem = sem_get($semId, $concurrency);
+			sem_acquire($sem);
+			return $sem;
+		}
+		return false;
+	}
+
+	/**
+	 * @param resource $sem
+	 * @return bool
+	 */
+	public static function unguardWithSemaphore($sem) {
+		if (!is_resource($sem)) {
+			return false;
+		}
+		if (extension_loaded('sysvsem')) {
+			return sem_release($sem);
+		}
+		return false;
+	}
+
 	/**
 	 * @param ISimpleFolder $previewFolder
 	 * @param File $file
@@ -241,8 +272,13 @@ private function getMaxPreview(ISimpleFolder $previewFolder, File $file, $mimeTy
 				$maxWidth = (int)$this->config->getSystemValue('preview_max_x', 4096);
 				$maxHeight = (int)$this->config->getSystemValue('preview_max_y', 4096);
 
+				$previewConcurrency = $this->config->getSystemValueInt('preview_concurrency_new', 4);
+				$sem = self::guardWithSemaphore(self::SEMAPHORE_ID_NEW, $previewConcurrency);
+
 				$preview = $this->helper->getThumbnail($provider, $file, $maxWidth, $maxHeight);
 
+				self::unguardWithSemaphore($sem);
+
 				if (!($preview instanceof IImage)) {
 					continue;
 				}
@@ -407,6 +443,9 @@ private function generatePreview(ISimpleFolder $previewFolder, IImage $maxPrevie
 			throw new \InvalidArgumentException('Failed to generate preview, failed to load image');
 		}
 
+		$previewConcurrency = $this->config->getSystemValueInt('preview_concurrency_new', 4);
+		$sem = self::guardWithSemaphore(self::SEMAPHORE_ID_NEW, $previewConcurrency);
+
 		if ($crop) {
 			if ($height !== $preview->height() && $width !== $preview->width()) {
 				//Resize
@@ -429,6 +468,7 @@ private function generatePreview(ISimpleFolder $previewFolder, IImage $maxPrevie
 			$preview = $maxPreview->resizeCopy(max($width, $height));
 		}
 
+		self::unguardWithSemaphore($sem);
 
 		$path = $this->generatePath($width, $height, $crop, $preview->dataMimeType(), $prefix);
 		try {

diff --git a/lib/private/PreviewManager.php b/lib/private/PreviewManager.php
@@ -187,7 +187,14 @@ private function getGenerator(): Generator {
 	 * @since 11.0.0 - \InvalidArgumentException was added in 12.0.0
 	 */
 	public function getPreview(File $file, $width = -1, $height = -1, $crop = false, $mode = IPreview::MODE_FILL, $mimeType = null) {
-		return $this->getGenerator()->getPreview($file, $width, $height, $crop, $mode, $mimeType);
+		$previewConcurrency = $this->config->getSystemValueInt('preview_concurrency_all', 8);
+		$sem = Generator::guardWithSemaphore(Generator::SEMAPHORE_ID_ALL, $previewConcurrency);
+
+		$preview = $this->getGenerator()->getPreview($file, $width, $height, $crop, $mode, $mimeType);
+
+		Generator::unguardWithSemaphore($sem);
+
+		return $preview;
 	}
 
 	/**