[FEATURE] minify task: Use workerpool for terser

Based on #700

* Changed logging to verbose
* Added option 'useWorkers' to processor. Implicit activation through
  taskUtil parameter seemed a bit odd. Moved that to the minify task
* Added JSDoc

lib/processors/minifier.js

@@ -1,21 +1,44 @@
+import path from "node:path";
+import {fileURLToPath} from "node:url";
 import posixPath from "node:path/posix";
-import {minify} from "terser";
+import os from "node:os";
+import workerpool from "workerpool";
 import Resource from "@ui5/fs/Resource";
+import logger from "@ui5/logger";
+const log = logger.getLogger("builder:processors:minifier");
 
-/**
- * Preserve comments which contain:
- * <ul>
- *  <li>copyright notice</li>
- *  <li>license terms</li>
- *  <li>"@ui5-bundle"</li>
- *  <li>"@ui5-bundle-raw-include"</li>
- * </ul>
- *
- * @type {RegExp}
- */
-const copyrightCommentsAndBundleCommentPattern = /copyright|\(c\)(?:[0-9]+|\s+[0-9A-Za-z])|released under|license|\u00a9|^@ui5-bundle-raw-include |^@ui5-bundle /i;
 const debugFileRegex = /((?:\.view|\.fragment|\.controller|\.designtime|\.support)?\.js)$/;
 
+const MIN_WORKERS = 2;
+const MAX_WORKERS = 4;
+const osCpus = os.cpus().length || 1;
+const maxWorkers = Math.max(Math.min(osCpus - 1, MAX_WORKERS), MIN_WORKERS);
+
+// Shared workerpool across all executions until the taskUtil cleanup is triggered
+let pool;
+
+function getPool(taskUtil) {
+	if (!pool) {
+		log.verbose(`Creating workerpool with up to ${maxWorkers} workers (available CPU cores: ${osCpus})`);
+		const workerPath = path.join(path.dirname(fileURLToPath(import.meta.url)), "minifierWorker.js");
+		pool = workerpool.pool(workerPath, {
+			workerType: "auto",
+			maxWorkers
+		});
+		taskUtil.registerCleanupTask(() => {
+			log.verbose(`Terminating workerpool`);
+			const poolToBeTerminated = pool;
+			pool = null;
+			poolToBeTerminated.terminate();
+		});
+	}
+	return pool;
+}
+
+async function minifyInWorker(options, taskUtil) {
+	return getPool(taskUtil).exec("execMinification", [options]);
+}
+
 /**
  * @public
  * @module @ui5/builder/processors/minifier
@@ -40,57 +63,56 @@ const debugFileRegex = /((?:\.view|\.fragment|\.controller|\.designtime|\.suppor
  *
  * @param {object} parameters Parameters
  * @param {@ui5/fs/Resource[]} parameters.resources List of resources to be processed
+ * @param {@ui5/builder/tasks/TaskUtil|object} [parameters.taskUtil] TaskUtil instance.
+ *    Requred when using the <code>useWorkers</code> option
  * @param {object} [parameters.options] Options
  * @param {boolean} [parameters.options.addSourceMappingUrl=true]
- * 				Whether to add a sourceMappingURL reference to the end of the minified resource
+ *   Whether to add a sourceMappingURL reference to the end of the minified resource
+ * @param {boolean} [parameters.options.useWorkers=false]
+ *  Whether to offload the minification task onto separate CPU threads. This often speeds up the build process
  * @returns {Promise<module:@ui5/builder/processors/minifier~MinifierResult[]>}
- * 				Promise resolving with object of resource, dbgResource and sourceMap
+ *   Promise resolving with object of resource, dbgResource and sourceMap
  */
-export default async function({resources, options: {addSourceMappingUrl = true} = {}}) {
+export default async function({resources, taskUtil, options: {addSourceMappingUrl = true, useWorkers = false} = {}}) {
+	let minify;
+	if (useWorkers) {
+		if (!taskUtil) {
+			// TaskUtil is required for worker support
+			throw new Error(`Minifier: Option 'useWorkers' requires a taskUtil instance to be provided`);
+		}
+		minify = minifyInWorker;
+	} else {
+		// Do not use workerpool
+		minify = (await import("./minifierWorker.js")).default;
+	}
+
 	return Promise.all(resources.map(async (resource) => {
 		const dbgPath = resource.getPath().replace(debugFileRegex, "-dbg$1");
 		const dbgResource = await resource.clone();
 		dbgResource.setPath(dbgPath);
 
 		const filename = posixPath.basename(resource.getPath());
 		const code = await resource.getString();
-		try {
-			const sourceMapOptions = {
-				filename
-			};
-			if (addSourceMappingUrl) {
-				sourceMapOptions.url = filename + ".map";
-			}
-			const dbgFilename = posixPath.basename(dbgPath);
-			const result = await minify({
-				// Use debug-name since this will be referenced in the source map "sources"
-				[dbgFilename]: code
-			}, {
-				output: {
-					comments: copyrightCommentsAndBundleCommentPattern,
-					wrap_func_args: false
-				},
-				compress: false,
-				mangle: {
-					reserved: [
-						"jQuery",
-						"jquery",
-						"sap",
-					]
-				},
-				sourceMap: sourceMapOptions
-			});
-			resource.setString(result.code);
-			const sourceMapResource = new Resource({
-				path: resource.getPath() + ".map",
-				string: result.map
-			});
-			return {resource, dbgResource, sourceMapResource};
-		} catch (err) {
-			// Note: err.filename contains the debug-name
-			throw new Error(
-				`Minification failed with error: ${err.message} in file ${filename} ` +
-				`(line ${err.line}, col ${err.col}, pos ${err.pos})`);
+
+		const sourceMapOptions = {
+			filename
+		};
+		if (addSourceMappingUrl) {
+			sourceMapOptions.url = filename + ".map";
 		}
+		const dbgFilename = posixPath.basename(dbgPath);
+
+		const result = await minify({
+			filename,
+			dbgFilename,
+			code,
+			sourceMapOptions
+		}, taskUtil);
+		resource.setString(result.code);
+		const sourceMapResource = new Resource({
+			path: resource.getPath() + ".map",
+			string: result.map
+		});
+		return {resource, dbgResource, sourceMapResource};
 	}));
 }

lib/processors/minifierWorker.js

@@ -0,0 +1,75 @@
+import workerpool from "workerpool";
+import {minify} from "terser";
+
+/**
+ * @private
+ * @module @ui5/builder/tasks/minifyWorker
+ */
+
+/**
+ * Preserve comments which contain:
+ * <ul>
+ *  <li>copyright notice</li>
+ *  <li>license terms</li>
+ *  <li>"@ui5-bundle"</li>
+ *  <li>"@ui5-bundle-raw-include"</li>
+ * </ul>
+ *
+ * @type {RegExp}
+ */
+const copyrightCommentsAndBundleCommentPattern = /copyright|\(c\)(?:[0-9]+|\s+[0-9A-Za-z])|released under|license|\u00a9|^@ui5-bundle-raw-include |^@ui5-bundle /i;
+
+/**
+ * Task to minify resources.
+ *
+ * @private
+ * @function default
+ * @static
+ *
+ * @param {object} parameters Parameters
+ * @param {string} parameters.filename
+ * @param {string} parameters.dbgFilename
+ * @param {string} parameters.code
+ * @param {object} parameters.sourceMapOptions
+ * @returns {Promise<undefined>} Promise resolving once minification of the resource has finished
+ */
+export default async function execMinification({
+	filename,
+	dbgFilename,
+	code,
+	sourceMapOptions
+}) {
+	try {
+		return await minify({
+			// Use debug-name since this will be referenced in the source map "sources"
+			[dbgFilename]: code
+		}, {
+			output: {
+				comments: copyrightCommentsAndBundleCommentPattern,
+				wrap_func_args: false
+			},
+			compress: false,
+			mangle: {
+				reserved: [
+					"jQuery",
+					"jquery",
+					"sap",
+				]
+			},
+			sourceMap: sourceMapOptions
+		});
+	} catch (err) {
+		// Note: err.filename contains the debug-name
+		throw new Error(
+			`Minification failed with error: ${err.message} in file ${filename} ` +
+			`(line ${err.line}, col ${err.col}, pos ${err.pos})`);
+	}
+}
+
+if (!workerpool.isMainThread) {
+	// Script got loaded through workerpool
+	// => Create a worker and register public functions
+	workerpool.worker({
+		execMinification
+	});
+}

lib/tasks/minify.js

@@ -25,8 +25,10 @@ export default async function({workspace, taskUtil, options: {pattern, omitSourc
 	const resources = await workspace.byGlob(pattern);
 	const processedResources = await minifier({
 		resources,
+		taskUtil,
 		options: {
-			addSourceMappingUrl: !omitSourceMapResources
+			addSourceMappingUrl: !omitSourceMapResources,
+			useWorkers: !!taskUtil,
 		}
 	});
 

package.json

@@ -131,6 +131,7 @@
 		"rimraf": "^4.1.1",
 		"semver": "^7.3.8",
 		"terser": "^5.16.1",
+		"workerpool": "^6.3.1",
 		"xml2js": "^0.4.23"
 	},
 	"devDependencies": {

test/lib/tasks/minify.js

@@ -31,7 +31,8 @@ test("integration: minify omitSourceMapResources=true", async (t) => {
 			HasDebugVariant: "1️⃣",
 			IsDebugVariant: "2️⃣",
 			OmitFromBuildResult: "3️⃣"
-		}
+		},
+		registerCleanupTask: sinon.stub()
 	};
 	const {reader, writer, workspace} = createWorkspace();
 	const content = `