Use ShutdownHook to gracefully handle JVM shutdown

in all classes which already registered their own shutdown hook
- CloneCommand
- GC#PidLock
- FS#FileStoreAttributes
- LocalDiskRepositoryTestCase#Cleanup

Change-Id: I3efc1f83f3cbbf43eeeaaedcd2bee1ef31971a72

3 files changed, 19 insertions, 36 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java
index 107b00e274..3e034f1a6a 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java
@@ -29,6 +29,7 @@ import org.eclipse.jgit.dircache.DirCacheCheckout;
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.internal.util.ShutdownHook;
 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.BranchConfig.BranchRebaseMode;
 import org.eclipse.jgit.lib.ConfigConstants;
@@ -100,6 +101,8 @@ public class CloneCommand extends TransportCommand<CloneCommand, Git> {
 
 	private List<String> shallowExcludes = new ArrayList<>();
 
+	private ShutdownHook.Listener shutdownListener = this::cleanup;
+
 	private enum FETCH_TYPE {
 		MULTIPLE_BRANCHES, ALL_BRANCHES, MIRROR
 	}
@@ -181,12 +184,7 @@ public class CloneCommand extends TransportCommand<CloneCommand, Git> {
 		@SuppressWarnings("resource") // Closed by caller
 		Repository repository = init();
 		FetchResult fetchResult = null;
-		Thread cleanupHook = new Thread(() -> cleanup());
-		try {
-			Runtime.getRuntime().addShutdownHook(cleanupHook);
-		} catch (IllegalStateException e) {
-			// ignore - the VM is already shutting down
-		}
+		ShutdownHook.INSTANCE.register(shutdownListener);
 		try {
 			fetchResult = fetch(repository, u);
 		} catch (IOException ioe) {
@@ -210,11 +208,7 @@ public class CloneCommand extends TransportCommand<CloneCommand, Git> {
 			cleanup();
 			throw e;
 		} finally {
-			try {
-				Runtime.getRuntime().removeShutdownHook(cleanupHook);
-			} catch (IllegalStateException e) {
-				// ignore - the VM is already shutting down
-			}
+			ShutdownHook.INSTANCE.unregister(shutdownListener);
 		}
 		try {
 			checkout(repository, fetchResult);
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
index fd9e550526..6933bfb3d4 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
@@ -75,6 +75,7 @@ import org.eclipse.jgit.internal.storage.commitgraph.CommitGraphWriter;
 import org.eclipse.jgit.internal.storage.commitgraph.GraphCommits;
 import org.eclipse.jgit.internal.storage.pack.PackExt;
 import org.eclipse.jgit.internal.storage.pack.PackWriter;
+import org.eclipse.jgit.internal.util.ShutdownHook;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.CoreConfig;
@@ -1799,7 +1800,7 @@ public class GC {
 
 		private FileChannel channel;
 
-		private Thread cleanupHook;
+		private ShutdownHook.Listener shutdownListener = this::close;
 
 		PidLock() {
 			pidFile = repo.getDirectory().toPath().resolve(GC_PID);
@@ -1829,12 +1830,7 @@ public class GC {
 				}
 				channel.write(ByteBuffer
 						.wrap(getProcDesc().getBytes(StandardCharsets.UTF_8)));
-				try {
-					Runtime.getRuntime().addShutdownHook(
-							cleanupHook = new Thread(() -> close()));
-				} catch (IllegalStateException e) {
-					// ignore - the VM is already shutting down
-				}
+				ShutdownHook.INSTANCE.register(shutdownListener);
 			} catch (IOException | OverlappingFileLockException e) {
 				try {
 					failedToLock();
@@ -1903,13 +1899,7 @@ public class GC {
 		public void close() {
 			boolean wasLocked = false;
 			try {
-				if (cleanupHook != null) {
-					try {
-						Runtime.getRuntime().removeShutdownHook(cleanupHook);
-					} catch (IllegalStateException e) {
-						// ignore - the VM is already shutting down
-					}
-				}
+				ShutdownHook.INSTANCE.unregister(shutdownListener);
 				if (lock != null && lock.isValid()) {
 					lock.release();
 					wasLocked = true;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
index b8fc4fc1e2..3e95de1459 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
@@ -67,6 +67,7 @@ import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.errors.LockFailedException;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.internal.storage.file.FileSnapshot;
+import org.eclipse.jgit.internal.util.ShutdownHook;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Constants;
@@ -301,18 +302,16 @@ public abstract class FS {
 
 		static {
 			// Shut down the SAVE_RUNNER on System.exit()
+			ShutdownHook.INSTANCE
+					.register(FileStoreAttributes::shutdownSafeRunner);
+		}
+
+		private static void shutdownSafeRunner() {
 			try {
-				Runtime.getRuntime().addShutdownHook(new Thread(() -> {
-					try {
-						SAVE_RUNNER.shutdownNow();
-						SAVE_RUNNER.awaitTermination(100,
-								TimeUnit.MILLISECONDS);
-					} catch (Exception e) {
-						// Ignore; we're shutting down
-					}
-				}));
-			} catch (IllegalStateException e) {
-				// ignore - may fail if shutdown is already in progress
+				SAVE_RUNNER.shutdownNow();
+				SAVE_RUNNER.awaitTermination(100, TimeUnit.MILLISECONDS);
+			} catch (Exception e) {
+				// Ignore; we're shutting down
 			}
 		}