avoid leaking memory after the compiler has been closed

clear cache on shutdown

lib/Compiler.js

@@ -1101,6 +1101,10 @@ ${other}`);
 	close(callback) {
 		this.hooks.shutdown.callAsync(err => {
 			if (err) return callback(err);
+			// Get rid of reference to last compilation to avoid leaking memory
+			// We can't run this._cleanupLastCompilation() as the Stats to this compilation
+			// might be still in use. We try to get rid for the reference to the cache instead.
+			this._lastCompilation = undefined;
 			this.cache.shutdown(callback);
 		});
 	}

lib/FileSystemInfo.js

@@ -412,6 +412,14 @@ class SnapshotOptimization {
 		} times referenced)`;
 	}
 
+	clear() {
+		this._map.clear();
+		this._statItemsShared = 0;
+		this._statItemsUnshared = 0;
+		this._statSharedSnapshots = 0;
+		this._statReusedSharedSnapshots = 0;
+	}
+
 	storeUnsharedSnapshot(snapshot, locations) {
 		if (locations === undefined) return;
 		const optimizationEntry = {
@@ -984,6 +992,42 @@ class FileSystemInfo {
 		}
 	}
 
+	clear() {
+		this._remainingLogs = this.logger ? 40 : 0;
+		if (this._loggedPaths !== undefined) this._loggedPaths.clear();
+
+		this._snapshotCache = new WeakMap();
+		this._fileTimestampsOptimization.clear();
+		this._fileHashesOptimization.clear();
+		this._fileTshsOptimization.clear();
+		this._contextTimestampsOptimization.clear();
+		this._contextHashesOptimization.clear();
+		this._contextTshsOptimization.clear();
+		this._missingExistenceOptimization.clear();
+		this._managedItemInfoOptimization.clear();
+		this._managedFilesOptimization.clear();
+		this._managedContextsOptimization.clear();
+		this._managedMissingOptimization.clear();
+		this._fileTimestamps.clear();
+		this._fileHashes.clear();
+		this._fileTshs.clear();
+		this._contextTimestamps.clear();
+		this._contextHashes.clear();
+		this._contextTshs.clear();
+		this._managedItems.clear();
+		this._managedItems.clear();
+
+		this._cachedDeprecatedFileTimestamps = undefined;
+		this._cachedDeprecatedContextTimestamps = undefined;
+
+		this._statCreatedSnapshots = 0;
+		this._statTestedSnapshotsCached = 0;
+		this._statTestedSnapshotsNotCached = 0;
+		this._statTestedChildrenCached = 0;
+		this._statTestedChildrenNotCached = 0;
+		this._statTestedEntries = 0;
+	}
+
 	/**
 	 * @param {Map<string, FileSystemInfoEntry | "ignore" | null>} map timestamps
 	 * @returns {void}

lib/cache/IdleFileCachePlugin.js

@@ -30,7 +30,7 @@ class IdleFileCachePlugin {
 	 * @returns {void}
 	 */
 	apply(compiler) {
-		const strategy = this.strategy;
+		let strategy = this.strategy;
 		const idleTimeout = this.idleTimeout;
 		const idleTimeoutForInitialStore = Math.min(
 			idleTimeout,
@@ -101,7 +101,10 @@ class IdleFileCachePlugin {
 						reportProgress(1, `stored`);
 					});
 				}
-				return currentIdlePromise;
+				return currentIdlePromise.then(() => {
+					// Reset strategy
+					if (strategy.clear) strategy.clear();
+				});
 			}
 		);
 

lib/cache/MemoryCachePlugin.js

@@ -46,6 +46,12 @@ class MemoryCachePlugin {
 				});
 			}
 		);
+		compiler.cache.hooks.shutdown.tap(
+			{ name: "MemoryCachePlugin", stage: Cache.STAGE_MEMORY },
+			() => {
+				cache.clear();
+			}
+		);
 	}
 }
 module.exports = MemoryCachePlugin;

lib/cache/PackFileCacheStrategy.js

@@ -763,6 +763,11 @@ class PackFileCacheStrategy {
 		this.packPromise = this._openPack();
 	}
 
+	_getPack() {
+		if (this.packPromise === undefined) this.packPromise = this._openPack();
+		return this.packPromise;
+	}
+
 	/**
 	 * @returns {Promise<Pack>} the pack
 	 */
@@ -925,7 +930,7 @@ class PackFileCacheStrategy {
 	 * @returns {Promise<void>} promise
 	 */
 	store(identifier, etag, data) {
-		return this.packPromise.then(pack => {
+		return this._getPack().then(pack => {
 			pack.set(identifier, etag === null ? null : etag.toString(), data);
 		});
 	}
@@ -936,7 +941,7 @@ class PackFileCacheStrategy {
 	 * @returns {Promise<any>} promise to the cached content
 	 */
 	restore(identifier, etag) {
-		return this.packPromise
+		return this._getPack()
 			.then(pack =>
 				pack.get(identifier, etag === null ? null : etag.toString())
 			)
@@ -955,6 +960,7 @@ class PackFileCacheStrategy {
 	}
 
 	afterAllStored() {
+		if (this.packPromise === undefined) return Promise.resolve();
 		const reportProgress = ProgressPlugin.getReporter(this.compiler);
 		return this.packPromise
 			.then(pack => {
@@ -1114,6 +1120,16 @@ class PackFileCacheStrategy {
 				this.logger.debug(err.stack);
 			});
 	}
+
+	clear() {
+		this.fileSystemInfo.clear();
+		this.buildDependencies.clear();
+		this.newBuildDependencies.clear();
+		this.resolveBuildDependenciesSnapshot = undefined;
+		this.resolveResults = undefined;
+		this.buildSnapshot = undefined;
+		this.packPromise = undefined;
+	}
 }
 
 module.exports = PackFileCacheStrategy;

types.d.ts

@@ -3760,6 +3760,7 @@ declare abstract class FileSystemInfo {
 	immutablePaths: string[];
 	immutablePathsWithSlash: string[];
 	logStatistics(): void;
+	clear(): void;
 	addFileTimestamps(
 		map: Map<string, null | FileSystemInfoEntry | "ignore">
 	): void;