Merge branch 'stable-4.4'

* stable-4.4:
  Log if Repository.useCnt becomes negative
  Time based eviction strategy for repository cache
  Add method to read time unit from config
  Align include.path max depth with native git
  Config load should not fail on unsupported or nonexistent include path
  Allow using JDK 7 bootclasspath when compiling JGit using Java 8
  Extract work queue to allow reusing it

Change-Id: I6aeedb1cb8b0c3068af344a719c80a03ae68fc23
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ConfigTest.java

@@ -788,10 +788,31 @@ public class ConfigTest {
 
 	@Test
 	public void testIncludeValuePathNotFound() throws ConfigInvalidException {
+		// we do not expect an exception, included path not found are ignored
 		String notFound = "/not/found";
-		expectedEx.expect(ConfigInvalidException.class);
-		expectedEx.expectMessage(notFound);
-		parse("[include]\npath=" + notFound + "\n");
+		Config parsed = parse("[include]\npath=" + notFound + "\n");
+		assertEquals(1, parsed.getSections().size());
+		assertEquals(notFound, parsed.getString("include", null, "path"));
+	}
+
+	@Test
+	public void testIncludeValuePathWithTilde() throws ConfigInvalidException {
+		// we do not expect an exception, included path not supported are
+		// ignored
+		String notSupported = "~/someFile";
+		Config parsed = parse("[include]\npath=" + notSupported + "\n");
+		assertEquals(1, parsed.getSections().size());
+		assertEquals(notSupported, parsed.getString("include", null, "path"));
+	}
+
+	@Test
+	public void testIncludeValuePathRelative() throws ConfigInvalidException {
+		// we do not expect an exception, included path not supported are
+		// ignored
+		String notSupported = "someRelativeFile";
+		Config parsed = parse("[include]\npath=" + notSupported + "\n");
+		assertEquals(1, parsed.getSections().size());
+		assertEquals(notSupported, parsed.getString("include", null, "path"));
 	}
 
 	@Test

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/RepositoryCacheConfigTest.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2016 Ericsson
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.lib;
+
+import static org.eclipse.jgit.lib.RepositoryCacheConfig.AUTO_CLEANUP_DELAY;
+import static org.eclipse.jgit.lib.RepositoryCacheConfig.NO_CLEANUP;
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.junit.Before;
+import org.junit.Test;
+
+public class RepositoryCacheConfigTest {
+
+	private RepositoryCacheConfig config;
+
+	@Before
+	public void setUp() {
+		config = new RepositoryCacheConfig();
+	}
+
+	@Test
+	public void testDefaultValues() {
+		assertEquals(TimeUnit.HOURS.toMillis(1), config.getExpireAfter());
+		assertEquals(config.getExpireAfter() / 10, config.getCleanupDelay());
+	}
+
+	@Test
+	public void testCleanupDelay() {
+		config.setCleanupDelay(TimeUnit.HOURS.toMillis(1));
+		assertEquals(TimeUnit.HOURS.toMillis(1), config.getCleanupDelay());
+	}
+
+	@Test
+	public void testAutoCleanupDelay() {
+		config.setExpireAfter(TimeUnit.MINUTES.toMillis(20));
+		config.setCleanupDelay(AUTO_CLEANUP_DELAY);
+		assertEquals(TimeUnit.MINUTES.toMillis(20), config.getExpireAfter());
+		assertEquals(config.getExpireAfter() / 10, config.getCleanupDelay());
+	}
+
+	@Test
+	public void testAutoCleanupDelayShouldBeMax10minutes() {
+		config.setExpireAfter(TimeUnit.HOURS.toMillis(10));
+		assertEquals(TimeUnit.HOURS.toMillis(10), config.getExpireAfter());
+		assertEquals(TimeUnit.MINUTES.toMillis(10), config.getCleanupDelay());
+	}
+
+	@Test
+	public void testDisabledCleanupDelay() {
+		config.setCleanupDelay(NO_CLEANUP);
+		assertEquals(NO_CLEANUP, config.getCleanupDelay());
+	}
+
+	@Test
+	public void testFromConfig() throws ConfigInvalidException {
+		Config otherConfig = new Config();
+		otherConfig.fromText("[core]\nrepositoryCacheExpireAfter=1000\n"
+				+ "repositoryCacheCleanupDelay=500");
+		config.fromConfig(otherConfig);
+		assertEquals(1000, config.getExpireAfter());
+		assertEquals(500, config.getCleanupDelay());
+	}
+}

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/RepositoryCacheTest.java

@@ -196,17 +196,80 @@ public class RepositoryCacheTest extends RepositoryTestCase {
 	}
 
 	@Test
-	public void testRepositoryUnregisteringWhenClosing() throws Exception {
+	public void testRepositoryNotUnregisteringWhenClosing() throws Exception {
 		FileKey loc = FileKey.exact(db.getDirectory(), db.getFS());
 		Repository d2 = RepositoryCache.open(loc);
 		assertEquals(1, d2.useCnt.get());
 		assertThat(RepositoryCache.getRegisteredKeys(),
 				hasItem(FileKey.exact(db.getDirectory(), db.getFS())));
 		assertEquals(1, RepositoryCache.getRegisteredKeys().size());
-
 		d2.close();
-
 		assertEquals(0, d2.useCnt.get());
-		assertEquals(0, RepositoryCache.getRegisteredKeys().size());
+		assertEquals(1, RepositoryCache.getRegisteredKeys().size());
+		assertTrue(RepositoryCache.isCached(d2));
+	}
+
+	@Test
+	public void testRepositoryUnregisteringWhenExpired() throws Exception {
+		Repository repoA = createBareRepository();
+		Repository repoB = createBareRepository();
+		Repository repoC = createBareRepository();
+		RepositoryCache.register(repoA);
+		RepositoryCache.register(repoB);
+		RepositoryCache.register(repoC);
+
+		assertEquals(3, RepositoryCache.getRegisteredKeys().size());
+		assertTrue(RepositoryCache.isCached(repoA));
+		assertTrue(RepositoryCache.isCached(repoB));
+		assertTrue(RepositoryCache.isCached(repoC));
+
+		// fake that repoA was closed more than 1 hour ago (default expiration
+		// time)
+		repoA.close();
+		repoA.closedAt.set(System.currentTimeMillis() - 65 * 60 * 1000);
+		// close repoB but this one will not be expired
+		repoB.close();
+
+		assertEquals(3, RepositoryCache.getRegisteredKeys().size());
+		assertTrue(RepositoryCache.isCached(repoA));
+		assertTrue(RepositoryCache.isCached(repoB));
+		assertTrue(RepositoryCache.isCached(repoC));
+
+		RepositoryCache.clearExpired();
+
+		assertEquals(2, RepositoryCache.getRegisteredKeys().size());
+		assertFalse(RepositoryCache.isCached(repoA));
+		assertTrue(RepositoryCache.isCached(repoB));
+		assertTrue(RepositoryCache.isCached(repoC));
+	}
+
+	@Test
+	public void testReconfigure() throws InterruptedException {
+		RepositoryCache.register(db);
+		assertTrue(RepositoryCache.isCached(db));
+		db.close();
+		assertTrue(RepositoryCache.isCached(db));
+
+		// Actually, we would only need to validate that
+		// WorkQueue.getExecutor().scheduleWithFixedDelay is called with proper
+		// values but since we do not have a mock library, we test
+		// reconfiguration from a black box perspective. I.e. reconfigure
+		// expireAfter and cleanupDelay to 1 ms and wait until the Repository
+		// is evicted to prove that reconfiguration worked.
+		RepositoryCacheConfig config = new RepositoryCacheConfig();
+		config.setExpireAfter(1);
+		config.setCleanupDelay(1);
+		config.install();
+
+		// Instead of using a fixed waiting time, start with small and increase:
+		// sleep 1, 2, 4, 8, 16, ..., 1024 ms
+		// This wait will time out after 2048 ms
+		for (int i = 0; i <= 10; i++) {
+			Thread.sleep(1 << i);
+			if (!RepositoryCache.isCached(db)) {
+				return;
+			}
+		}
+		fail("Repository should have been evicted from cache");
 	}
 }

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -185,6 +185,7 @@ corruptObjectTruncatedInMode=truncated in mode
 corruptObjectTruncatedInName=truncated in name
 corruptObjectTruncatedInObjectId=truncated in object id
 corruptObjectZeroId=entry points to null SHA-1
+corruptUseCnt=close() called when useCnt is already zero
 couldNotCheckOutBecauseOfConflicts=Could not check out because of conflicts
 couldNotDeleteLockFileShouldNotHappen=Could not delete lock file. Should not happen
 couldNotDeleteTemporaryIndexFileShouldNotHappen=Could not delete temporary index file. Should not happen
@@ -339,7 +340,6 @@ invalidId0=Invalid id
 invalidIdLength=Invalid id length {0}; should be {1}
 invalidIgnoreParamSubmodule=Found invalid ignore param for submodule {0}.
 invalidIgnoreRule=Exception caught while parsing ignore rule ''{0}''.
-invalidIncludedPathInConfigFile=Invalid included path in config file: {0}
 invalidIntegerValue=Invalid integer value: {0}.{1}={2}
 invalidKey=Invalid key: {0}
 invalidLineInConfigFile=Invalid line in config file

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -245,6 +245,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String corruptObjectTruncatedInObjectId;
 	/***/ public String corruptObjectZeroId;
 	/***/ public String corruptPack;
+	/***/ public String corruptUseCnt;
 	/***/ public String couldNotCheckOutBecauseOfConflicts;
 	/***/ public String couldNotDeleteLockFileShouldNotHappen;
 	/***/ public String couldNotDeleteTemporaryIndexFileShouldNotHappen;
@@ -398,7 +399,6 @@ public class JGitText extends TranslationBundle {
 	/***/ public String invalidIdLength;
 	/***/ public String invalidIgnoreParamSubmodule;
 	/***/ public String invalidIgnoreRule;
-	/***/ public String invalidIncludedPathInConfigFile;
 	/***/ public String invalidIntegerValue;
 	/***/ public String invalidKey;
 	/***/ public String invalidLineInConfigFile;

org.eclipse.jgit/src/org/eclipse/jgit/lib/BatchingProgressMonitor.java

@@ -43,55 +43,11 @@
 
 package org.eclipse.jgit.lib;
 
-import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
-import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 
 /** ProgressMonitor that batches update events. */
 public abstract class BatchingProgressMonitor implements ProgressMonitor {
-	private static final ScheduledThreadPoolExecutor alarmQueue;
-
-	static final Object alarmQueueKiller;
-
-	static {
-		// To support garbage collection, start our thread but
-		// swap out the thread factory. When our class is GC'd
-		// the alarmQueueKiller will finalize and ask the executor
-		// to shutdown, ending the worker.
-		//
-		int threads = 1;
-		alarmQueue = new ScheduledThreadPoolExecutor(threads,
-				new ThreadFactory() {
-					private final ThreadFactory baseFactory = Executors
-							.defaultThreadFactory();
-
-					public Thread newThread(Runnable taskBody) {
-						Thread thr = baseFactory.newThread(taskBody);
-						thr.setName("JGit-AlarmQueue"); //$NON-NLS-1$
-						thr.setDaemon(true);
-						return thr;
-					}
-				});
-		alarmQueue.setContinueExistingPeriodicTasksAfterShutdownPolicy(false);
-		alarmQueue.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
-		alarmQueue.prestartAllCoreThreads();
-
-		// Now that the threads are running, its critical to swap out
-		// our own thread factory for one that isn't in the ClassLoader.
-		// This allows the class to GC.
-		//
-		alarmQueue.setThreadFactory(Executors.defaultThreadFactory());
-
-		alarmQueueKiller = new Object() {
-			@Override
-			protected void finalize() {
-				alarmQueue.shutdownNow();
-			}
-		};
-	}
-
 	private long delayStartTime;
 
 	private TimeUnit delayStartUnit = TimeUnit.MILLISECONDS;
@@ -219,7 +175,7 @@ public abstract class BatchingProgressMonitor implements ProgressMonitor {
 
 		void delay(long time, TimeUnit unit) {
 			display = false;
-			timerFuture = alarmQueue.schedule(this, time, unit);
+			timerFuture = WorkQueue.getExecutor().schedule(this, time, unit);
 		}
 
 		public void run() {
@@ -254,7 +210,8 @@ public abstract class BatchingProgressMonitor implements ProgressMonitor {
 
 		private void restartTimer() {
 			display = false;
-			timerFuture = alarmQueue.schedule(this, 1, TimeUnit.SECONDS);
+			timerFuture = WorkQueue.getExecutor().schedule(this, 1,
+					TimeUnit.SECONDS);
 		}
 
 		void end(BatchingProgressMonitor pm) {

org.eclipse.jgit/src/org/eclipse/jgit/lib/Config.java

@@ -52,6 +52,7 @@
 package org.eclipse.jgit.lib;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.text.MessageFormat;
 import java.util.ArrayList;
@@ -82,7 +83,7 @@ public class Config {
 	private static final long KiB = 1024;
 	private static final long MiB = 1024 * KiB;
 	private static final long GiB = 1024 * MiB;
-	private static final int MAX_DEPTH = 999;
+	private static final int MAX_DEPTH = 10;
 
 	/** the change listeners */
 	private final ListenerList listeners = new ListenerList();
@@ -1247,9 +1248,15 @@ public class Config {
 				decoded = RawParseUtils.decode(bytes);
 			}
 			newEntries.addAll(fromTextRecurse(decoded, depth + 1));
+		} catch (FileNotFoundException fnfe) {
+			if (path.exists()) {
+				throw new ConfigInvalidException(MessageFormat
+						.format(JGitText.get().cannotReadFile, path), fnfe);
+			}
 		} catch (IOException ioe) {
-			throw new ConfigInvalidException(MessageFormat.format(
-					JGitText.get().invalidIncludedPathInConfigFile, path));
+			throw new ConfigInvalidException(
+					MessageFormat.format(JGitText.get().cannotReadFile, path),
+					ioe);
 		}
 	}
 

org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java

@@ -63,6 +63,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 
 import org.eclipse.jgit.annotations.NonNull;
 import org.eclipse.jgit.annotations.Nullable;
@@ -93,6 +94,8 @@ import org.eclipse.jgit.util.IO;
 import org.eclipse.jgit.util.RawParseUtils;
 import org.eclipse.jgit.util.SystemReader;
 import org.eclipse.jgit.util.io.SafeBufferedOutputStream;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Represents a Git repository.
@@ -103,6 +106,8 @@ import org.eclipse.jgit.util.io.SafeBufferedOutputStream;
  * This class is thread-safe.
  */
 public abstract class Repository implements AutoCloseable {
+	private static Logger LOG = LoggerFactory.getLogger(Repository.class);
+
 	private static final ListenerList globalListeners = new ListenerList();
 
 	/** @return the global listener list observing all events in this JVM. */
@@ -113,6 +118,8 @@ public abstract class Repository implements AutoCloseable {
 	/** Use counter */
 	final AtomicInteger useCnt = new AtomicInteger(1);
 
+	final AtomicLong closedAt = new AtomicLong();
+
 	/** Metadata directory holding the repository's critical files. */
 	private final File gitDir;
 
@@ -863,9 +870,24 @@ public abstract class Repository implements AutoCloseable {
 
 	/** Decrement the use count, and maybe close resources. */
 	public void close() {
-		if (useCnt.decrementAndGet() == 0) {
-			doClose();
-			RepositoryCache.unregister(this);
+		int newCount = useCnt.decrementAndGet();
+		if (newCount == 0) {
+			if (RepositoryCache.isCached(this)) {
+				closedAt.set(System.currentTimeMillis());
+			} else {
+				doClose();
+			}
+		} else if (newCount == -1) {
+			// should not happen, only log when useCnt became negative to
+			// minimize number of log entries
+			LOG.warn(JGitText.get().corruptUseCnt);
+			if (LOG.isDebugEnabled()) {
+				IllegalStateException e = new IllegalStateException();
+				LOG.debug("", e); //$NON-NLS-1$
+			}
+			if (RepositoryCache.isCached(this)) {
+				closedAt.set(System.currentTimeMillis());
+			}
 		}
 	}
 

org.eclipse.jgit/src/org/eclipse/jgit/lib/RepositoryCache.java

@@ -52,17 +52,26 @@ import java.util.Collection;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
+import org.eclipse.jgit.annotations.NonNull;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.internal.storage.file.FileRepository;
 import org.eclipse.jgit.util.FS;
 import org.eclipse.jgit.util.IO;
 import org.eclipse.jgit.util.RawParseUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /** Cache of active {@link Repository} instances. */
 public class RepositoryCache {
 	private static final RepositoryCache cache = new RepositoryCache();
 
+	private final static Logger LOG = LoggerFactory
+			.getLogger(RepositoryCache.class);
+
 	/**
 	 * Open an existing repository, reusing a cached instance if possible.
 	 * <p>
@@ -138,10 +147,10 @@ public class RepositoryCache {
 	 * @param db
 	 *            repository to unregister.
 	 */
-	public static void close(final Repository db) {
+	public static void close(@NonNull final Repository db) {
 		if (db.getDirectory() != null) {
 			FileKey key = FileKey.exact(db.getDirectory(), db.getFS());
-			cache.unregisterAndCloseRepository(key);
+			cache.unregisterAndCloseRepository(key, db);
 		}
 	}
 
@@ -187,20 +196,69 @@ public class RepositoryCache {
 		return cache.getKeys();
 	}
 
+	static boolean isCached(@NonNull Repository repo) {
+		File gitDir = repo.getDirectory();
+		if (gitDir == null) {
+			return false;
+		}
+		FileKey key = new FileKey(gitDir, repo.getFS());
+		Reference<Repository> repoRef = cache.cacheMap.get(key);
+		return repoRef != null && repoRef.get() == repo;
+	}
+
 	/** Unregister all repositories from the cache. */
 	public static void clear() {
 		cache.clearAll();
 	}
 
+	static void clearExpired() {
+		cache.clearAllExpired();
+	}
+
+	static void reconfigure(RepositoryCacheConfig repositoryCacheConfig) {
+		cache.configureEviction(repositoryCacheConfig);
+	}
+
 	private final ConcurrentHashMap<Key, Reference<Repository>> cacheMap;
 
 	private final Lock[] openLocks;
 
+	private ScheduledFuture<?> cleanupTask;
+
+	private volatile long expireAfter;
+
 	private RepositoryCache() {
 		cacheMap = new ConcurrentHashMap<Key, Reference<Repository>>();
 		openLocks = new Lock[4];
-		for (int i = 0; i < openLocks.length; i++)
+		for (int i = 0; i < openLocks.length; i++) {
 			openLocks[i] = new Lock();
+		}
+		configureEviction(new RepositoryCacheConfig());
+	}
+
+	private void configureEviction(
+			RepositoryCacheConfig repositoryCacheConfig) {
+		expireAfter = repositoryCacheConfig.getExpireAfter();
+		ScheduledThreadPoolExecutor scheduler = WorkQueue.getExecutor();
+		synchronized (scheduler) {
+			if (cleanupTask != null) {
+				cleanupTask.cancel(false);
+			}
+			long delay = repositoryCacheConfig.getCleanupDelay();
+			if (delay == RepositoryCacheConfig.NO_CLEANUP) {
+				return;
+			}
+			cleanupTask = scheduler.scheduleWithFixedDelay(new Runnable() {
+				@Override
+				public void run() {
+					try {
+						cache.clearAllExpired();
+					} catch (Throwable e) {
+						LOG.error(e.getMessage(), e);
+					}
+				}
+			}, delay, delay, TimeUnit.MILLISECONDS);
+		}
 	}
 
 	@SuppressWarnings("resource")
@@ -239,10 +297,20 @@ public class RepositoryCache {
 		return oldRef != null ? oldRef.get() : null;
 	}
 
-	private void unregisterAndCloseRepository(final Key location) {
-		Repository oldDb = unregisterRepository(location);
-		if (oldDb != null) {
-			oldDb.close();
+	private boolean isExpired(Repository db) {
+		return db != null && db.useCnt.get() == 0
+			&& (System.currentTimeMillis() - db.closedAt.get() > expireAfter);
+	}
+
+	private void unregisterAndCloseRepository(final Key location,
+			Repository db) {
+		synchronized (lockFor(location)) {
+			if (isExpired(db)) {
+				Repository oldDb = unregisterRepository(location);
+				if (oldDb != null) {
+					oldDb.close();
+				}
+			}
 		}
 	}
 
@@ -250,6 +318,15 @@ public class RepositoryCache {
 		return new ArrayList<Key>(cacheMap.keySet());
 	}
 
+	private void clearAllExpired() {
+		for (Reference<Repository> ref : cacheMap.values()) {
+			Repository db = ref.get();
+			if (isExpired(db)) {
+				RepositoryCache.close(db);
+			}
+		}
+	}
+
 	private void clearAll() {
 		for (int stage = 0; stage < 2; stage++) {
 			for (Iterator<Map.Entry<Key, Reference<Repository>>> i = cacheMap

org.eclipse.jgit/src/org/eclipse/jgit/lib/RepositoryCacheConfig.java

@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2016 Ericsson
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.lib;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Configuration parameters for JVM-wide repository cache used by JGit.
+ *
+ * @since 4.4
+ */
+public class RepositoryCacheConfig {
+
+	/**
+	 * Set cleanupDelayMillis to this value in order to switch off time-based
+	 * cache eviction. The JVM can still expire cache entries when heap memory
+	 * runs low.
+	 */
+	public static final long NO_CLEANUP = 0;
+
+	/**
+	 * Set cleanupDelayMillis to this value in order to auto-set it to minimum
+	 * of 1/10 of expireAfterMillis and 10 minutes
+	 */
+	public static final long AUTO_CLEANUP_DELAY = -1;
+
+	private long expireAfterMillis;
+
+	private long cleanupDelayMillis;
+
+	/** Create a default configuration. */
+	public RepositoryCacheConfig() {
+		expireAfterMillis = TimeUnit.HOURS.toMillis(1);
+		cleanupDelayMillis = AUTO_CLEANUP_DELAY;
+	}
+
+	/**
+	 * @return the time an unused repository should expired and be evicted from
+	 *         the RepositoryCache in milliseconds. <b>Default is 1 hour.</b>
+	 */
+	public long getExpireAfter() {
+		return expireAfterMillis;
+	}
+
+	/**
+	 * @param expireAfterMillis
+	 *            the time an unused repository should expired and be evicted
+	 *            from the RepositoryCache in milliseconds.
+	 */
+	public void setExpireAfter(long expireAfterMillis) {
+		this.expireAfterMillis = expireAfterMillis;
+	}
+
+	/**
+	 * @return the delay between the periodic cleanup of expired repository in
+	 *         milliseconds. <b>Default is minimum of 1/10 of expireAfterMillis
+	 *         and 10 minutes</b>
+	 */
+	public long getCleanupDelay() {
+		if (cleanupDelayMillis < 0) {
+			return Math.min(expireAfterMillis / 10,
+					TimeUnit.MINUTES.toMillis(10));
+		}
+		return cleanupDelayMillis;
+	}
+
+	/**
+	 * @param cleanupDelayMillis
+	 *            the delay between the periodic cleanup of expired repository
+	 *            in milliseconds. Set it to {@link #AUTO_CLEANUP_DELAY} to
+	 *            automatically derive cleanup delay from expireAfterMillis.
+	 *            <p>
+	 *            Set it to {@link #NO_CLEANUP} in order to switch off cache
+	 *            expiration.
+	 *            <p>
+	 *            If cache expiration is switched off the JVM still can evict
+	 *            cache entries when the JVM is running low on available heap
+	 *            memory.
+	 */
+	public void setCleanupDelay(long cleanupDelayMillis) {
+		this.cleanupDelayMillis = cleanupDelayMillis;
+	}
+
+	/**
+	 * Update properties by setting fields from the configuration.
+	 * <p>
+	 * If a property is not defined in the configuration, then it is left
+	 * unmodified.
+	 *
+	 * @param config
+	 *            configuration to read properties from.
+	 * @return {@code this}.
+	 */
+	public RepositoryCacheConfig fromConfig(Config config) {
+		setExpireAfter(
+				config.getTimeUnit("core", null, "repositoryCacheExpireAfter", //$NON-NLS-1$//$NON-NLS-2$
+						getExpireAfter(), TimeUnit.MILLISECONDS));
+		setCleanupDelay(
+				config.getTimeUnit("core", null, "repositoryCacheCleanupDelay", //$NON-NLS-1$ //$NON-NLS-2$
+						AUTO_CLEANUP_DELAY, TimeUnit.MILLISECONDS));
+		return this;
+	}
+
+	/**
+	 * Install this configuration as the live settings.
+	 * <p>
+	 * The new configuration is applied immediately.
+	 */
+	public void install() {
+		RepositoryCache.reconfigure(this);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/lib/WorkQueue.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2008-2016, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.lib;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.ThreadFactory;
+
+/**
+ * Simple work queue to run tasks in the background
+ */
+class WorkQueue {
+	private static final ScheduledThreadPoolExecutor executor;
+
+	static final Object executorKiller;
+
+	static {
+		// To support garbage collection, start our thread but
+		// swap out the thread factory. When our class is GC'd
+		// the executorKiller will finalize and ask the executor
+		// to shutdown, ending the worker.
+		//
+		int threads = 1;
+		executor = new ScheduledThreadPoolExecutor(threads,
+				new ThreadFactory() {
+					private final ThreadFactory baseFactory = Executors
+							.defaultThreadFactory();
+
+					public Thread newThread(Runnable taskBody) {
+						Thread thr = baseFactory.newThread(taskBody);
+						thr.setName("JGit-WorkQueue"); //$NON-NLS-1$
+						thr.setDaemon(true);
+						return thr;
+					}
+				});
+		executor.setRemoveOnCancelPolicy(true);
+		executor.setContinueExistingPeriodicTasksAfterShutdownPolicy(false);
+		executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
+		executor.prestartAllCoreThreads();
+
+		// Now that the threads are running, its critical to swap out
+		// our own thread factory for one that isn't in the ClassLoader.
+		// This allows the class to GC.
+		//
+		executor.setThreadFactory(Executors.defaultThreadFactory());
+
+		executorKiller = new Object() {
+			@Override
+			protected void finalize() {
+				executor.shutdownNow();
+			}
+		};
+	}
+
+	static ScheduledThreadPoolExecutor getExecutor() {
+		return executor;
+	}
+}

pom.xml

@@ -188,9 +188,10 @@
 
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
-
     <maven.build.timestamp.format>yyyyMMddHHmm</maven.build.timestamp.format>
     <bundle-manifest>${project.build.directory}/META-INF/MANIFEST.MF</bundle-manifest>
+    <!-- set JDK_HOME to JAVA_HOME path of JDK7 installation in order to compile against JDK 7 class library -->
+    <JDK_HOME>${JAVA_HOME}</JDK_HOME>
 
     <jgit-last-release-version>4.2.0.201601211800-r</jgit-last-release-version>
     <jsch-version>0.1.53</jsch-version>
@@ -264,6 +265,9 @@
             <encoding>UTF-8</encoding>
             <source>1.7</source>
             <target>1.7</target>
+            <compilerArguments>
+              <bootclasspath>${JDK_HOME}${file.separator}jre${file.separator}lib${file.separator}rt.jar${path.separator}${JDK_HOME}${file.separator}jre${file.separator}lib${file.separator}jsse.jar${path.separator}${JDK_HOME}${file.separator}jre${file.separator}lib${file.separator}jce.jar</bootclasspath>
+            </compilerArguments>
           </configuration>
         </plugin>