webpack/lib/cache/IdleFileCachePlugin.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const Cache = require("../Cache");
const ProgressPlugin = require("../ProgressPlugin");

/** @typedef {import("../Compiler")} Compiler */

const BUILD_DEPENDENCIES_KEY = Symbol();

class IdleFileCachePlugin {
	/**
	 * @param {TODO} strategy cache strategy
	 * @param {number} idleTimeout timeout
	 * @param {number} idleTimeoutForInitialStore initial timeout
	 */
	constructor(strategy, idleTimeout, idleTimeoutForInitialStore) {
		this.strategy = strategy;
		this.idleTimeout = idleTimeout;
		this.idleTimeoutForInitialStore = idleTimeoutForInitialStore;
	}

	/**
	 * Apply the plugin
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		const strategy = this.strategy;
		const idleTimeout = this.idleTimeout;
		const idleTimeoutForInitialStore = Math.min(
			idleTimeout,
			this.idleTimeoutForInitialStore
		);

		const resolvedPromise = Promise.resolve();

		/** @type {Map<string | typeof BUILD_DEPENDENCIES_KEY, () => Promise>} */
		const pendingIdleTasks = new Map();

		compiler.cache.hooks.store.tap(
			{ name: "IdleFileCachePlugin", stage: Cache.STAGE_DISK },
			(identifier, etag, data) => {
				pendingIdleTasks.set(identifier, () =>
					strategy.store(identifier, etag, data)
				);
			}
		);

		compiler.cache.hooks.get.tapPromise(
			{ name: "IdleFileCachePlugin", stage: Cache.STAGE_DISK },
			(identifier, etag, gotHandlers) => {
				return strategy.restore(identifier, etag).then(cacheEntry => {
					if (cacheEntry === undefined) {
						gotHandlers.push((result, callback) => {
							if (result !== undefined) {
								pendingIdleTasks.set(identifier, () =>
									strategy.store(identifier, etag, result)
								);
							}
							callback();
						});
					} else {
						return cacheEntry;
					}
				});
			}
		);

		compiler.cache.hooks.storeBuildDependencies.tap(
			{ name: "IdleFileCachePlugin", stage: Cache.STAGE_DISK },
			dependencies => {
				pendingIdleTasks.set(BUILD_DEPENDENCIES_KEY, () =>
					strategy.storeBuildDependencies(dependencies)
				);
			}
		);

		compiler.cache.hooks.shutdown.tapPromise(
			{ name: "IdleFileCachePlugin", stage: Cache.STAGE_DISK },
			() => {
				if (idleTimer) {
					clearTimeout(idleTimer);
					idleTimer = undefined;
				}
				isIdle = false;
				const reportProgress = ProgressPlugin.getReporter(compiler);
				const jobs = Array.from(pendingIdleTasks.values());
				if (reportProgress) reportProgress(0, "process pending cache items");
				const promises = jobs.map(fn => fn());
				pendingIdleTasks.clear();
				promises.push(currentIdlePromise);
				const promise = Promise.all(promises);
				currentIdlePromise = promise.then(() => strategy.afterAllStored());
				if (reportProgress) {
					currentIdlePromise = currentIdlePromise.then(() => {
						reportProgress(1, `stored`);
					});
				}
				return currentIdlePromise;
			}
		);

		/** @type {Promise<any>} */
		let currentIdlePromise = resolvedPromise;
		let isIdle = false;
		let isInitialStore = true;
		const processIdleTasks = () => {
			if (isIdle) {
				if (pendingIdleTasks.size > 0) {
					const promises = [currentIdlePromise];
					const maxTime = Date.now() + 100;
					let maxCount = 100;
					for (const [filename, factory] of pendingIdleTasks) {
						pendingIdleTasks.delete(filename);
						promises.push(factory());
						if (maxCount-- <= 0 || Date.now() > maxTime) break;
					}
					currentIdlePromise = Promise.all(promises);
					currentIdlePromise.then(() => {
						// Allow to exit the process between
						setTimeout(processIdleTasks, 0).unref();
					});
					return;
				}
				currentIdlePromise = currentIdlePromise.then(() =>
					strategy.afterAllStored()
				);
				isInitialStore = false;
			}
		};
		let idleTimer = undefined;
		compiler.cache.hooks.beginIdle.tap(
			{ name: "IdleFileCachePlugin", stage: Cache.STAGE_DISK },
			() => {
				idleTimer = setTimeout(
					() => {
						idleTimer = undefined;
						isIdle = true;
						resolvedPromise.then(processIdleTasks);
					},
					isInitialStore ? idleTimeoutForInitialStore : idleTimeout
				);
				idleTimer.unref();
			}
		);
		compiler.cache.hooks.endIdle.tap(
			{ name: "IdleFileCachePlugin", stage: Cache.STAGE_DISK },
			() => {
				if (idleTimer) {
					clearTimeout(idleTimer);
					idleTimer = undefined;
				}
				isIdle = false;
			}
		);
	}
}

module.exports = IdleFileCachePlugin;