[client] Memory management; handle OOM when hashing, do not skip blocks

Try to free some references regarding transfers earlier, e.g. the hash
worker and list of hashes as soon as hashing is finished on upload, not
only when the upload is finished and the window is closed.
Properly delay hashing of blocks in OOM scenarios, and be more
conservative with the number of hash workers, i.e. take maximum JVM
memory into account.
Also, improve thread naming.

13 files changed, 159 insertions, 57 deletions

diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/AsyncHashGenerator.java b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/AsyncHashGenerator.java
index cf593200..8ef12e12 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/AsyncHashGenerator.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/AsyncHashGenerator.java
@@ -13,6 +13,7 @@ import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -29,8 +30,9 @@ public class AsyncHashGenerator extends Thread {
 	private static final Logger LOGGER = LogManager.getLogger(AsyncHashGenerator.class);
 
 	private static final ThreadPoolExecutor HASH_WORK_POOL = new GrowingThreadPoolExecutor(1,
-			Math.max(1, Runtime.getRuntime().availableProcessors() - 1),
-			10, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(2),
+			Math.max(1, (int)Math.min(Runtime.getRuntime().availableProcessors() - 1,
+					Runtime.getRuntime().maxMemory() / (FileChunk.CHUNK_SIZE * 3))),
+			10, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(1),
 			new PrioThreadFactory("HashGen"), new ThreadPoolExecutor.CallerRunsPolicy());
 
 	private static final ThreadLocal<MessageDigest> SHA1_DIGESTER = new ThreadLocal<MessageDigest>() {
@@ -52,9 +54,13 @@ public class AsyncHashGenerator extends Thread {
 	private final List<FileChunk> chunkList;
 	private long nextReadMsg, nextDoneMsg, nextSendingMsg; // for debug spam :-(
 	private boolean readingDone = false;
-	private boolean hashingDone = false;
+	private AtomicInteger pendingHashes = new AtomicInteger();
 
 	private volatile boolean isCanceled = false;
+	
+	static {
+		LOGGER.info("Using " + HASH_WORK_POOL.getMaximumPoolSize() + " hash workers.");
+	}
 
 	public AsyncHashGenerator(File uploadFile) throws FileNotFoundException, NoSuchAlgorithmException {
 		try {
@@ -70,6 +76,15 @@ public class AsyncHashGenerator extends Thread {
 		setDaemon(true);
 		setName("HashGenerator");
 	}
+	
+	@Override
+	public synchronized void start() {
+		if (isCanceled) {
+			LOGGER.warn("Cannot start hashing if it has been cancelled before");
+		} else {
+			super.start();
+		}
+	}
 
 	public void setUploadToken(String token) {
 		if (!isCanceled && this.uploadToken == null) {
@@ -90,14 +105,15 @@ public class AsyncHashGenerator extends Thread {
 				}
 				Block block;
 				try {
-					byte[] buffer;
-					try {
-						buffer = new byte[chunk.range.getLength()];
-					} catch (OutOfMemoryError e) {
-						LOGGER.info("Low memory - slowing down hashing");
-						Util.sleep(5000);
-						continue;
-					}
+					byte[] buffer = null;
+					do {
+						try {
+							buffer = new byte[chunk.range.getLength()];
+						} catch (OutOfMemoryError e) {
+							LOGGER.info("Low memory - slowing down hashing");
+							Util.sleep(5000);
+						}
+					} while (buffer == null);
 					file.seek(chunk.range.startOffset);
 					file.readFully(buffer);
 					block = new Block(chunk, buffer);
@@ -111,23 +127,26 @@ public class AsyncHashGenerator extends Thread {
 				}
 				//
 				if (System.currentTimeMillis() > nextReadMsg) {
-					nextReadMsg = System.currentTimeMillis() + 30000;
+					nextReadMsg = System.currentTimeMillis() + 60000;
 					LOGGER.debug("Read chunk " + chunk.getChunkIndex());
 				}
 				//
 				for (;;) {
 					if (HASH_WORK_POOL.isTerminating() || HASH_WORK_POOL.isTerminated() || HASH_WORK_POOL.isShutdown()) {
 						LOGGER.warn("Aborting current hash job - pool has shut down");
+						isCanceled = true;
 						Thread.currentThread().interrupt();
 						return;
 					}
 					try {
+						pendingHashes.incrementAndGet();
 						HASH_WORK_POOL.execute(block);
 						// Don't hash too furiously in the background if the upload didn't start yet
 						if (uploadToken == null && chunk.getChunkIndex() > 4) {
 							Util.sleep(200);
 						}
 					} catch (RejectedExecutionException e) {
+						pendingHashes.decrementAndGet();
 						LOGGER.warn("Hash pool worker rejected a hash job!? Retrying...");
 						Util.sleep(1000);
 						continue;
@@ -142,7 +161,7 @@ public class AsyncHashGenerator extends Thread {
 		}
 	}
 
-	public void cancel() {
+	public synchronized void cancel() {
 		LOGGER.debug("Cancelled externally");
 		isCanceled = true;
 	}
@@ -152,7 +171,7 @@ public class AsyncHashGenerator extends Thread {
 	 */
 	private class Block implements Runnable {
 		public final FileChunk chunk;
-		public final byte[] buffer;
+		public byte[] buffer;
 
 		public Block(FileChunk chunk, byte[] buffer) {
 			this.chunk = chunk;
@@ -163,7 +182,14 @@ public class AsyncHashGenerator extends Thread {
 		public void run() {
 			MessageDigest digester = SHA1_DIGESTER.get();
 			digester.update(buffer, 0, chunk.range.getLength());
+			this.buffer = null; // Clear reference before calling function below
 			byte[] hash = digester.digest();
+			synchronized (this) {
+				if (isCanceled) {
+					pendingHashes.decrementAndGet();
+					return;
+				}
+			}
 			hashDone(chunk, hash);
 		}
 	}
@@ -180,7 +206,7 @@ public class AsyncHashGenerator extends Thread {
 		int chunkIndex = chunk.getChunkIndex();
 		boolean wasLastChunk = false;
 		if (System.currentTimeMillis() > nextDoneMsg) {
-			nextDoneMsg = System.currentTimeMillis() + 30000;
+			nextDoneMsg = System.currentTimeMillis() + 60000;
 			LOGGER.debug("Done hashing chunk " + chunkIndex);
 		}
 		synchronized (chunkHashes) {
@@ -224,8 +250,7 @@ public class AsyncHashGenerator extends Thread {
 				isCanceled = true;
 			}
 		}
-		if (wasLastChunk) {
-			hashingDone = true;
+		if (pendingHashes.decrementAndGet() == 0) {
 			cleanupIfDone();
 		}
 	}
@@ -235,15 +260,25 @@ public class AsyncHashGenerator extends Thread {
 	 * a reference to this class, at least we will not prevent this stuff from being
 	 * garbage collected.
 	 */
-	private void cleanupIfDone() {
-		if (uploadToken == null && !isCanceled)
+	private synchronized void cleanupIfDone() {
+		if (!readingDone && isAlive())
 			return;
-		if (!readingDone)
+		if (uploadToken == null && !isCanceled)
 			return;
-		if (!hashingDone && !isCanceled)
+		if (pendingHashes.get() != 0)
 			return;
+		isCanceled = true;
 		chunkHashes.clear();
 		chunkList.clear();
+		LOGGER.debug("Hasher cleaned up");
+	}
+	
+	/**
+	 * @return true if this instance is not dong anything meaningful anymore
+	 * and no reference to it needs to be kept around.
+	 */
+	public boolean canBeDiscarded() {
+		return isCanceled || (!isAlive() && pendingHashes.get() == 0);
 	}
 
 	/**
@@ -252,6 +287,8 @@ public class AsyncHashGenerator extends Thread {
 	 * @return false if the token is not known to the server
 	 */
 	private boolean submitHashes(boolean mustSucceed) {
+		if (isCanceled)
+			return true;
 		List<ByteBuffer> subList;
 		boolean d;
 		synchronized (chunkHashes) {
@@ -262,7 +299,7 @@ public class AsyncHashGenerator extends Thread {
 			d = System.currentTimeMillis() > nextSendingMsg;
 		}
 		if (d) {
-			nextSendingMsg = System.currentTimeMillis() + 30000;
+			nextSendingMsg = System.currentTimeMillis() + 60000;
 			LOGGER.debug("Preparing to send hash list to server (" + subList.size() + " / " + (uploadToken != null) + ")");
 		}
 		if (uploadToken == null || subList.isEmpty()) // No token yet, cannot submit, or empty list
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/DownloadTask.java b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/DownloadTask.java
index 0692f8a2..3b57222f 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/DownloadTask.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/DownloadTask.java
@@ -4,6 +4,7 @@ import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.RandomAccessFile;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -28,7 +29,9 @@ public class DownloadTask extends TransferTask {
 	 * Logger instance for this class.
 	 */
 	private final static Logger LOGGER = LogManager.getLogger(DownloadTask.class);
-
+	
+	private static final AtomicInteger THREAD_ID = new AtomicInteger();
+	
 	private final String host;
 	private final int port;
 	private final String downloadToken;
@@ -122,6 +125,10 @@ public class DownloadTask extends TransferTask {
 	private class DownloadThread extends TransferThread {
 		private Downloader downloader = null;
 		private DownloadHandler cb = new DownloadHandler();
+		
+		public DownloadThread() {
+			super("UpConn#" + THREAD_ID.incrementAndGet());
+		}
 
 		@Override
 		public void run() {
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/TransferTask.java b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/TransferTask.java
index cca42929..4f7ed6fe 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/TransferTask.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/TransferTask.java
@@ -69,7 +69,7 @@ public abstract class TransferTask implements Runnable, TransferEventEmitter {
 			ensureActivity();
 			Util.sleep(UPDATE_INTERVAL_MS);
 		}
-		LOGGER.info("Transfer worker mainloop finished");
+		LOGGER.debug("Transfer worker mainloop finished");
 		List<TransferThread> joinList = new ArrayList<>();
 		synchronized (transfers) {
 			isCancelled = true;
@@ -85,7 +85,7 @@ public abstract class TransferTask implements Runnable, TransferEventEmitter {
 			Util.joinThread(t);
 		}
 		cleanup();
-		LOGGER.info("Trasfer worker exiting");
+		LOGGER.info("Transfer worker exiting");
 	}
 
 	protected void cleanup() {
@@ -197,7 +197,7 @@ public abstract class TransferTask implements Runnable, TransferEventEmitter {
 	protected final void connectFailed(TransferThread thread) {
 		synchronized (transfers) {
 			connectingTransfers.remove(thread);
-			LOGGER.info("Establishing new transfer connection failed, [a:" + transfers.size() + "/c:"
+			LOGGER.debug("Establishing new transfer connection failed, [a:" + transfers.size() + "/c:"
 					+ connectingTransfers.size() + "]");
 		}
 	}
@@ -207,7 +207,7 @@ public abstract class TransferTask implements Runnable, TransferEventEmitter {
 			connectingTransfers.remove(thread);
 			if (!isCancelled) {
 				transfers.add(thread);
-				LOGGER.info("Establishing new transfer connection succeeded, [a:" + transfers.size() + "/c:"
+				LOGGER.debug("Establishing new transfer connection succeeded, [a:" + transfers.size() + "/c:"
 						+ connectingTransfers.size() + "]");
 				return;
 			}
@@ -219,7 +219,7 @@ public abstract class TransferTask implements Runnable, TransferEventEmitter {
 	protected final void transferEnded(TransferThread thread, boolean success) {
 		synchronized (transfers) {
 			transfers.remove(thread);
-			LOGGER.info("A transfer connection has finished (success=" + success + "), [a:" + transfers.size() + "/c:"
+			LOGGER.debug("A transfer connection has finished (success=" + success + "), [a:" + transfers.size() + "/c:"
 					+ connectingTransfers.size() + "]");
 			if (endgame && !success && transfers.isEmpty()) {
 				// We had a transfer that reported success before, so we assume there are no more pending blocks
@@ -262,6 +262,10 @@ public abstract class TransferTask implements Runnable, TransferEventEmitter {
 	}
 
 	protected abstract static class TransferThread extends Thread {
+		
+		public TransferThread(String name) {
+			super(name);
+		}
 		@Override
 		public abstract void run();
 
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/UploadTask.java b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/UploadTask.java
index d9d188a2..84b9b47a 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/UploadTask.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/filetransfer/UploadTask.java
@@ -25,6 +25,9 @@ public class UploadTask extends TransferTask {
 	 * Logger instance for this class.
 	 */
 	private final static Logger LOGGER = LogManager.getLogger(UploadTask.class);
+
+	private static final AtomicInteger THREAD_ID = new AtomicInteger();
+	
 	/**
 	 * Update interval of the block progress (needs thrift call to sat)
 	 */
@@ -64,6 +67,11 @@ public class UploadTask extends TransferTask {
 	}
 
 	private class UploadThread extends TransferThread {
+
+		public UploadThread() {
+			super("UpConn#" + THREAD_ID.incrementAndGet());
+		}
+
 		//		private long totalBytesRead = 0;
 		private long currentSpeed = 0;
 		private Uploader uploader = null;
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/MainWindow.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/MainWindow.java
index d8e7f797..4be287d7 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/MainWindow.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/MainWindow.java
@@ -255,19 +255,26 @@ public abstract class MainWindow {
 				@Override
 				public void fire() {
 					App.waitForInit();
-					// now try to init the session with the saved configuration (by giving it null)
-					if (ThriftActions.initSession(null, false, SwingUtilities.getWindowAncestor(mainWindow))) {
-						initWindow();
-					} else {
-						// session resume failed, so do the normal login procedure
-						Gui.asyncExec(new Runnable() {
-							@Override
-							public void run() {
-								LoginWindow.open(mainWindow);
+					Gui.syncExec(new GuiCallable<Boolean>() {
+						@Override
+						public Boolean run() {
+							// now try to init the session with the saved configuration (by giving it null)
+							if (ThriftActions.initSession(null, false,
+									SwingUtilities.getWindowAncestor(mainWindow))) {
 								initWindow();
+							} else {
+								// session resume failed, so do the normal login procedure
+								Gui.asyncExec(new Runnable() {
+									@Override
+									public void run() {
+										LoginWindow.open(mainWindow);
+										initWindow();
+									}
+								});
 							}
-						});
-					}
+							return null;
+						}
+					});
 				}
 			});
 		}
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/DownloadPanel.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/DownloadPanel.java
index a25bd661..a50e67c5 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/DownloadPanel.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/DownloadPanel.java
@@ -69,5 +69,10 @@ public class DownloadPanel extends TransferPanel implements ActionListener, Quit
 	public void onApplicationQuit() {
 		download.cancel();
 	}
+	
+	@Override
+	protected void releaseResources() {
+		// NOOP
+	}
 
 }
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/PassiveUploadPanel.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/PassiveUploadPanel.java
index bfd9b783..93b412de 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/PassiveUploadPanel.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/PassiveUploadPanel.java
@@ -38,4 +38,9 @@ public class PassiveUploadPanel extends TransferPanel {
 		return false;
 	}
 	
+	@Override
+	protected void releaseResources() {
+		// NOOP
+	}
+	
 }
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/TransferPanel.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/TransferPanel.java
index 0718946e..95464f24 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/TransferPanel.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/TransferPanel.java
@@ -129,11 +129,13 @@ public abstract class TransferPanel extends ActivityPanel implements TransferEve
 						status = I18n.ACTIVITY.getString("TransferPanel.TransferState.error");
 						if (transfer.isCanceled()) {
 							transfer.removeListener(panel);
+							releaseResources();
 						}
 						break;
 					case FINISHED:
 						transferDone();
 						status = I18n.ACTIVITY.getString("TransferPanel.TransferState.finished");
+						releaseResources();
 						break;
 					case IDLE:
 						status = I18n.ACTIVITY.getString("TransferPanel.TransferState.idle");
@@ -166,6 +168,11 @@ public abstract class TransferPanel extends ActivityPanel implements TransferEve
 			}
 		});
 	}
+	
+	/**
+	 * Called when the transfer is finished, or cancelled due to an error
+	 */
+	protected abstract void releaseResources();
 
 	private void transferDone() {
 		transfer.removeListener(panel);
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/UploadPanel.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/UploadPanel.java
index 6b8c5a94..7e56b0e8 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/UploadPanel.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/activity/UploadPanel.java
@@ -34,7 +34,7 @@ public class UploadPanel extends TransferPanel implements QuitNotification {
 
 	private static final Logger LOGGER = LogManager.getLogger(UploadPanel.class);
 
-	private final UploadInitiator state;
+	private UploadInitiator state;
 
 	private final UploadPanel panel = this;
 	
@@ -59,26 +59,33 @@ public class UploadPanel extends TransferPanel implements QuitNotification {
 	private class ButtonAction implements ActionListener {
 		@Override
 		public void actionPerformed(ActionEvent e) {
+			if (state == null)
+				return;
+			state.getUploadTask().removeListener(panel);
 			if (!state.getUploadTask().isCanceled()) {
 				if (!Gui.showMessageBox(panel, I18n.ACTIVITY.getString("UploadPanel.Message.yesNo.cancelTransfer"),
 						MessageType.QUESTION_YESNO, null, null))
 					return;
+				final UploadInitiator fstate = state;
 				QuickTimer.scheduleOnce(new Task() {
 					@Override
 					public void fire() {
-						state.cancelError("UploadPanel: Requested by user through button press");
+						fstate.cancelError("UploadPanel: Requested by user through button press");
 					}
 				});
 			}
-			state.getUploadTask().removeListener(panel);
 			close();
+			state = null;
 		}
 	}
 
 	private class SscToggle implements ActionListener {
 		@Override
 		public void actionPerformed(ActionEvent e) {
+			if (state == null)
+				return;
 			final UploadOptions options = new UploadOptions(chkServerSideCopy.isSelected());
+			final UploadInitiator fstate = state;
 			QuickTimer.scheduleOnce(new Task() {
 				@Override
 				public void fire() {
@@ -86,7 +93,7 @@ public class UploadPanel extends TransferPanel implements QuitNotification {
 					UploadOptions newOpt = null;
 					try {
 						newOpt = ThriftManager.getSatClient().setUploadOptions(Session.getSatelliteToken(),
-								state.getToken(), options);
+								fstate.getToken(), options);
 					} catch (TAuthorizationException | TInvalidTokenException e) {
 						dis = true;
 					} catch (TException e) {
@@ -117,6 +124,13 @@ public class UploadPanel extends TransferPanel implements QuitNotification {
 	@Override
 	public void onApplicationQuit() {
 		// Application quit, tell server we cancel
+		if (state == null)
+			return;
 		state.cancelError("Application quit (via UploadPanel)");
 	}
+	
+	@Override
+	protected void releaseResources() {
+		state = null;
+	}
 }
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageCreationWizard.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageCreationWizard.java
index 0bfe2b22..0c56a5c0 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageCreationWizard.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageCreationWizard.java
@@ -291,22 +291,24 @@ public class ImageCreationWizard extends Wizard implements UiFeedback, QuitNotif
 	}
 
 	@Override protected boolean onCancelRequest() {
-		if (state.uuid == null)
+		if (state == null || state.uuid == null)
 			return true; // Allow closing - nothing in progress
 		boolean confirmed = Gui.showMessageBox(this,
 				I18n.WIZARD.getString("ImageCreation.Message.yesNo.cancelRequest"),
 				MessageType.QUESTION_YESNO, null, null);
 		if (confirmed) {
 			QuickTimer.scheduleOnce(new Task() {
-				@Override public void fire() {
-					if (state.upload != null) {
+				@Override
+				public void fire() {
+					if (state != null && state.upload != null) {
 						state.upload.cancelError("Cancelled through aborting wizard");
-					}
-					// As we're creating a new VM, delete base image aswell
-					try {
-						ThriftManager.getSatClient().deleteImageBase(Session.getSatelliteToken(), state.uuid);
-					} catch (TException e) {
-						LOGGER.debug("Error canceling upload on sat: ", e);
+						// As we're creating a new VM, delete base image aswell
+						try {
+							ThriftManager.getSatClient()
+									.deleteImageBase(Session.getSatelliteToken(), state.uuid);
+						} catch (TException e) {
+							LOGGER.debug("Error canceling upload on sat: ", e);
+						}
 					}
 				}
 			});
@@ -315,7 +317,7 @@ public class ImageCreationWizard extends Wizard implements UiFeedback, QuitNotif
 	}
 
 	@Override public boolean wantConfirmQuit() {
-		return state.uuid != null;
+		return state != null && state.uuid != null;
 	}
 
 	@Override public void escapePressed() {
@@ -330,7 +332,10 @@ public class ImageCreationWizard extends Wizard implements UiFeedback, QuitNotif
 
 	@Override
 	protected void doCleanup() {
-		state = null;
+		if (state != null) {
+			state.upload = null;
+			state = null;
+		}
 		containerDefinition = null;
 		currentPages.clear();
 	}
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageUpdateWizard.java b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageUpdateWizard.java
index ac8f80c1..1bcbaaf6 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageUpdateWizard.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/gui/wizard/ImageUpdateWizard.java
@@ -147,8 +147,11 @@ public class ImageUpdateWizard extends Wizard implements UiFeedback, QuitNotific
 
 	@Override
 	protected void doCleanup() {
+		if (state != null) {
+			state.upload = null;
+			state = null;
+		}
 		imageUploadPage = null;
-		state = null;
 	}
 
 }
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/ThriftActions.java b/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/ThriftActions.java
index d8efa252..c10a36bf 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/ThriftActions.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/ThriftActions.java
@@ -456,7 +456,7 @@ public class ThriftActions {
 					}
 				});
 
-				new Thread(dlTask).start();
+				new Thread(dlTask, "DownloadTask").start();
 
 				Config.setDownloadPath(destDir.getParentFile().getAbsolutePath());
 				if (callback != null)
diff --git a/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/UploadInitiator.java b/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/UploadInitiator.java
index efa65bab..811eb447 100644
--- a/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/UploadInitiator.java
+++ b/dozentenmodul/src/main/java/org/openslx/dozmod/thrift/UploadInitiator.java
@@ -174,7 +174,7 @@ public class UploadInitiator {
 					return;
 				}
 				uploadTask.setMinConnections(Config.getTransferConnectionCount());
-				Thread uploadThread = new Thread(uploadTask);
+				Thread uploadThread = new Thread(uploadTask, "UploadTask");
 				uploadThread.setDaemon(true);
 				uploadThread.start();
 			}