Refactor ValidationManager and fix some bugs. #619

briar-core/src/org/briarproject/blogs/BlogManagerImpl.java

@@ -59,12 +59,12 @@ import static org.briarproject.api.blogs.BlogConstants.KEY_COMMENT;
 import static org.briarproject.api.blogs.BlogConstants.KEY_DESCRIPTION;
 import static org.briarproject.api.blogs.BlogConstants.KEY_ORIGINAL_MSG_ID;
 import static org.briarproject.api.blogs.BlogConstants.KEY_ORIGINAL_PARENT_MSG_ID;
+import static org.briarproject.api.blogs.BlogConstants.KEY_PARENT_MSG_ID;
 import static org.briarproject.api.blogs.BlogConstants.KEY_PUBLIC_KEY;
 import static org.briarproject.api.blogs.BlogConstants.KEY_READ;
 import static org.briarproject.api.blogs.BlogConstants.KEY_TIMESTAMP;
 import static org.briarproject.api.blogs.BlogConstants.KEY_TIME_RECEIVED;
 import static org.briarproject.api.blogs.BlogConstants.KEY_TYPE;
-import static org.briarproject.api.blogs.BlogConstants.KEY_PARENT_MSG_ID;
 import static org.briarproject.api.blogs.MessageType.COMMENT;
 import static org.briarproject.api.blogs.MessageType.POST;
 import static org.briarproject.api.blogs.MessageType.WRAPPED_COMMENT;
@@ -298,8 +298,7 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 			meta.put(KEY_TIMESTAMP, p.getMessage().getTimestamp());
 			meta.put(KEY_AUTHOR, authorToBdfDictionary(p.getAuthor()));
 			meta.put(KEY_READ, true);
-			clientHelper.addLocalMessage(txn, p.getMessage(), CLIENT_ID, meta,
-					true);
+			clientHelper.addLocalMessage(txn, p.getMessage(), meta, true);
 
 			// broadcast event about new post
 			GroupId groupId = p.getMessage().getGroupId();
@@ -346,7 +345,7 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 			meta.put(KEY_AUTHOR, authorToBdfDictionary(author));
 
 			// Send comment
-			clientHelper.addLocalMessage(txn, message, CLIENT_ID, meta, true);
+			clientHelper.addLocalMessage(txn, message, meta, true);
 
 			// broadcast event
 			BlogPostHeader h =
@@ -429,7 +428,7 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 		meta.put(KEY_TIME_RECEIVED, pOriginalHeader.getTimeReceived());
 
 		// Send wrapped message and store metadata
-		clientHelper.addLocalMessage(txn, wMessage, CLIENT_ID, meta, true);
+		clientHelper.addLocalMessage(txn, wMessage, meta, true);
 		return wMessage.getId();
 	}
 

briar-core/src/org/briarproject/blogs/BlogPostValidator.java

@@ -32,9 +32,9 @@ import static org.briarproject.api.blogs.BlogConstants.KEY_AUTHOR;
 import static org.briarproject.api.blogs.BlogConstants.KEY_AUTHOR_ID;
 import static org.briarproject.api.blogs.BlogConstants.KEY_AUTHOR_NAME;
 import static org.briarproject.api.blogs.BlogConstants.KEY_COMMENT;
+import static org.briarproject.api.blogs.BlogConstants.KEY_ORIGINAL_MSG_ID;
 import static org.briarproject.api.blogs.BlogConstants.KEY_ORIGINAL_PARENT_MSG_ID;
 import static org.briarproject.api.blogs.BlogConstants.KEY_PARENT_MSG_ID;
-import static org.briarproject.api.blogs.BlogConstants.KEY_ORIGINAL_MSG_ID;
 import static org.briarproject.api.blogs.BlogConstants.KEY_PUBLIC_KEY;
 import static org.briarproject.api.blogs.BlogConstants.KEY_READ;
 import static org.briarproject.api.blogs.BlogConstants.KEY_TIMESTAMP;
@@ -114,7 +114,7 @@ class BlogPostValidator extends BdfMessageValidator {
 		BdfDictionary meta = new BdfDictionary();
 		meta.put(KEY_ORIGINAL_MSG_ID, m.getId());
 		meta.put(KEY_AUTHOR, authorToBdfDictionary(a));
-		return new BdfMessageContext(meta, null);
+		return new BdfMessageContext(meta);
 	}
 
 	private BdfMessageContext validateComment(Message m, Group g, BdfList body)
@@ -197,7 +197,7 @@ class BlogPostValidator extends BdfMessageValidator {
 		meta.put(KEY_ORIGINAL_MSG_ID, wMessage.getId());
 		meta.put(KEY_TIMESTAMP, wTimestamp);
 		meta.put(KEY_AUTHOR, c.getDictionary().getDictionary(KEY_AUTHOR));
-		return new BdfMessageContext(meta, null);
+		return new BdfMessageContext(meta);
 	}
 
 	private BdfMessageContext validateWrappedComment(Message m, Group g,

briar-core/src/org/briarproject/clients/ClientHelperImpl.java

@@ -18,7 +18,6 @@ import org.briarproject.api.db.DatabaseComponent;
 import org.briarproject.api.db.DbException;
 import org.briarproject.api.db.Metadata;
 import org.briarproject.api.db.Transaction;
-import org.briarproject.api.sync.ClientId;
 import org.briarproject.api.sync.GroupId;
 import org.briarproject.api.sync.Message;
 import org.briarproject.api.sync.MessageFactory;
@@ -62,11 +61,11 @@ class ClientHelperImpl implements ClientHelper {
 	}
 
 	@Override
-	public void addLocalMessage(Message m, ClientId c, BdfDictionary metadata,
+	public void addLocalMessage(Message m, BdfDictionary metadata,
 			boolean shared) throws DbException, FormatException {
 		Transaction txn = db.startTransaction(false);
 		try {
-			addLocalMessage(txn, m, c, metadata, shared);
+			addLocalMessage(txn, m, metadata, shared);
 			txn.setComplete();
 		} finally {
 			db.endTransaction(txn);
@@ -74,10 +73,10 @@ class ClientHelperImpl implements ClientHelper {
 	}
 
 	@Override
-	public void addLocalMessage(Transaction txn, Message m, ClientId c,
+	public void addLocalMessage(Transaction txn, Message m,
 			BdfDictionary metadata, boolean shared)
 			throws DbException, FormatException {
-		db.addLocalMessage(txn, m, c, metadataEncoder.encode(metadata), shared);
+		db.addLocalMessage(txn, m, metadataEncoder.encode(metadata), shared);
 	}
 
 	@Override

briar-core/src/org/briarproject/clients/MessageQueueManagerImpl.java

@@ -16,10 +16,10 @@ import org.briarproject.api.sync.Group;
 import org.briarproject.api.sync.GroupId;
 import org.briarproject.api.sync.InvalidMessageException;
 import org.briarproject.api.sync.Message;
+import org.briarproject.api.sync.MessageContext;
 import org.briarproject.api.sync.MessageId;
 import org.briarproject.api.sync.ValidationManager;
 import org.briarproject.api.sync.ValidationManager.IncomingMessageHook;
-import org.briarproject.api.sync.MessageContext;
 import org.briarproject.util.ByteUtils;
 
 import java.util.ArrayList;
@@ -70,7 +70,7 @@ class MessageQueueManagerImpl implements MessageQueueManager {
 		saveQueueState(txn, queue.getId(), queueState);
 		QueueMessage q = queueMessageFactory.createMessage(queue.getId(),
 				timestamp, queuePosition, body);
-		db.addLocalMessage(txn, q, queue.getClientId(), meta, true);
+		db.addLocalMessage(txn, q, meta, true);
 		return q;
 	}
 

briar-core/src/org/briarproject/db/Database.java

@@ -18,6 +18,7 @@ import org.briarproject.api.sync.MessageId;
 import org.briarproject.api.sync.MessageStatus;
 import org.briarproject.api.sync.ValidationManager.State;
 import org.briarproject.api.transport.TransportKeys;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.Collection;
 import java.util.Map;
@@ -83,10 +84,10 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Adds a dependency between two MessageIds
+	 * Adds a dependency between two messages in the given group.
 	 */
-	void addMessageDependency(T txn, MessageId dependentId,
-			MessageId dependencyId) throws DbException;
+	void addMessageDependency(T txn, GroupId g, MessageId dependent,
+			MessageId dependency) throws DbException;
 
 	/**
 	 * Records that a message has been offered by the given contact.
@@ -281,11 +282,13 @@ interface Database<T> {
 	Collection<LocalAuthor> getLocalAuthors(T txn) throws DbException;
 
 	/**
-	 * Returns the dependencies of the given message.
-	 * This method makes sure that dependencies in different groups
-	 * are returned as {@link ValidationManager.State.INVALID}. Note that this
-	 * is not set on the dependencies themselves; the returned states should
-	 * only be taken in the context of the given message.
+	 * Returns the IDs and states of all dependencies of the given message.
+	 * Missing dependencies have the state {@link
+	 * org.briarproject.api.sync.ValidationManager.State UNKNOWN}.
+	 * Dependencies in other groups have the state {@link
+	 * org.briarproject.api.sync.ValidationManager.State INVALID}.
+	 * Note that these states are not set on the dependencies themselves; the
+	 * returned states should only be taken in the context of the given message.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -293,7 +296,9 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns all IDs of messages that depend on the given message.
+	 * Returns all IDs and states of all dependents of the given message.
+	 * Messages in other groups that declare a dependency on the given message
+	 * will be returned even though such dependencies are invalid.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -350,6 +355,13 @@ interface Database<T> {
 	 */
 	Metadata getMessageMetadata(T txn, MessageId m) throws DbException;
 
+	/**
+	 * Returns the validation and delivery state of the given message.
+	 * <p/>
+	 * Read-only.
+	 */
+	State getMessageState(T txn, MessageId m) throws DbException;
+
 	/**
 	 * Returns the status of all messages in the given group with respect
 	 * to the given contact.
@@ -377,15 +389,6 @@ interface Database<T> {
 	Collection<MessageId> getMessagesToAck(T txn, ContactId c, int maxMessages)
 			throws DbException;
 
-	/**
-	 * Returns the IDs of any messages that need to be delivered to the given
-	 * client.
-	 * <p/>
-	 * Read-only.
-	 */
-	Collection<MessageId> getMessagesToDeliver(T txn, ClientId c)
-			throws DbException;
-
 	/**
 	 * Returns the IDs of some messages that are eligible to be offered to the
 	 * given contact, up to the given number of messages.
@@ -437,6 +440,7 @@ interface Database<T> {
 	 * <p/>
 	 * Read-only.
 	 */
+	@Nullable
 	byte[] getRawMessage(T txn, MessageId m) throws DbException;
 
 	/**
@@ -592,7 +596,7 @@ interface Database<T> {
 	 * Marks the given contact as active or inactive.
 	 */
 	void setContactActive(T txn, ContactId c, boolean active)
-		throws DbException;
+			throws DbException;
 
 	/**
 	 * Marks the given message as shared or unshared.
@@ -601,10 +605,9 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Marks the given message as valid or invalid.
+	 * Sets the validation and delivery state of the given message.
 	 */
-	void setMessageState(T txn, MessageId m, State state)
-			throws DbException;
+	void setMessageState(T txn, MessageId m, State state) throws DbException;
 
 	/**
 	 * Sets the reordering window for the given contact and transport in the

briar-core/src/org/briarproject/db/DatabaseComponentImpl.java

@@ -28,10 +28,10 @@ import org.briarproject.api.event.LocalAuthorRemovedEvent;
 import org.briarproject.api.event.MessageAddedEvent;
 import org.briarproject.api.event.MessageRequestedEvent;
 import org.briarproject.api.event.MessageSharedEvent;
+import org.briarproject.api.event.MessageStateChangedEvent;
 import org.briarproject.api.event.MessageToAckEvent;
 import org.briarproject.api.event.MessageToRequestEvent;
 import org.briarproject.api.event.MessagesAckedEvent;
-import org.briarproject.api.event.MessageStateChangedEvent;
 import org.briarproject.api.event.MessagesSentEvent;
 import org.briarproject.api.event.SettingsUpdatedEvent;
 import org.briarproject.api.identity.Author;
@@ -50,6 +50,7 @@ import org.briarproject.api.sync.Offer;
 import org.briarproject.api.sync.Request;
 import org.briarproject.api.sync.ValidationManager.State;
 import org.briarproject.api.transport.TransportKeys;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -188,7 +189,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		}
 	}
 
-	public void addLocalMessage(Transaction transaction, Message m, ClientId c,
+	public void addLocalMessage(Transaction transaction, Message m,
 			Metadata meta, boolean shared) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
@@ -197,7 +198,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (!db.containsMessage(txn, m.getId())) {
 			addMessage(txn, m, DELIVERED, shared);
 			transaction.attach(new MessageAddedEvent(m, null));
-			transaction.attach(new MessageStateChangedEvent(m, c, true,
+			transaction.attach(new MessageStateChangedEvent(m.getId(), true,
 					DELIVERED));
 			if (shared) transaction.attach(new MessageSharedEvent(m.getId()));
 		}
@@ -271,6 +272,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		db.deleteMessageMetadata(txn, m);
 	}
 
+	@Nullable
 	public Ack generateAck(Transaction transaction, ContactId c,
 			int maxMessages) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
@@ -283,6 +285,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return new Ack(ids);
 	}
 
+	@Nullable
 	public Collection<byte[]> generateBatch(Transaction transaction,
 			ContactId c, int maxLength, int maxLatency) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
@@ -301,6 +304,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return Collections.unmodifiableList(messages);
 	}
 
+	@Nullable
 	public Offer generateOffer(Transaction transaction, ContactId c,
 			int maxMessages, int maxLatency) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
@@ -313,6 +317,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return new Offer(ids);
 	}
 
+	@Nullable
 	public Request generateRequest(Transaction transaction, ContactId c,
 			int maxMessages) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
@@ -326,6 +331,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return new Request(ids);
 	}
 
+	@Nullable
 	public Collection<byte[]> generateRequestedBatch(Transaction transaction,
 			ContactId c, int maxLength, int maxLatency) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
@@ -420,18 +426,13 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getMessagesToValidate(txn, c);
 	}
 
-	public Collection<MessageId> getMessagesToDeliver(Transaction transaction,
-			ClientId c) throws DbException {
-		T txn = unbox(transaction);
-		return db.getMessagesToDeliver(txn, c);
-	}
-
 	public Collection<MessageId> getPendingMessages(Transaction transaction,
 			ClientId c) throws DbException {
 		T txn = unbox(transaction);
 		return db.getPendingMessages(txn, c);
 	}
 
+	@Nullable
 	public byte[] getRawMessage(Transaction transaction, MessageId m)
 			throws DbException {
 		T txn = unbox(transaction);
@@ -473,6 +474,14 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getMessageMetadataForValidator(txn, m);
 	}
 
+	public State getMessageState(Transaction transaction, MessageId m)
+			throws DbException {
+		T txn = unbox(transaction);
+		if (!db.containsMessage(txn, m))
+			throw new NoSuchMessageException();
+		return db.getMessageState(txn, m);
+	}
+
 	public Collection<MessageStatus> getMessageStatus(Transaction transaction,
 			ContactId c, GroupId g) throws DbException {
 		T txn = unbox(transaction);
@@ -720,14 +729,14 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (shared) transaction.attach(new MessageSharedEvent(m));
 	}
 
-	public void setMessageState(Transaction transaction, Message m, ClientId c,
+	public void setMessageState(Transaction transaction, MessageId m,
 			State state) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
-		if (!db.containsMessage(txn, m.getId()))
+		if (!db.containsMessage(txn, m))
 			throw new NoSuchMessageException();
-		db.setMessageState(txn, m.getId(), state);
-		transaction.attach(new MessageStateChangedEvent(m, c, false, state));
+		db.setMessageState(txn, m, state);
+		transaction.attach(new MessageStateChangedEvent(m, false, state));
 	}
 
 	public void addMessageDependencies(Transaction transaction,
@@ -737,8 +746,9 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsMessage(txn, dependent.getId()))
 			throw new NoSuchMessageException();
-		for (MessageId dependencyId : dependencies) {
-			db.addMessageDependency(txn, dependent.getId(), dependencyId);
+		for (MessageId dependency : dependencies) {
+			db.addMessageDependency(txn, dependent.getGroupId(),
+					dependent.getId(), dependency);
 		}
 	}
 

briar-core/src/org/briarproject/db/JdbcDatabase.java

@@ -25,6 +25,7 @@ import org.briarproject.api.transport.IncomingKeys;
 import org.briarproject.api.transport.OutgoingKeys;
 import org.briarproject.api.transport.TransportKeys;
 import org.briarproject.util.StringUtils;
+import org.jetbrains.annotations.Nullable;
 
 import java.security.SecureRandom;
 import java.sql.Connection;
@@ -53,7 +54,6 @@ import static org.briarproject.api.sync.ValidationManager.State.DELIVERED;
 import static org.briarproject.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.api.sync.ValidationManager.State.UNKNOWN;
-import static org.briarproject.api.sync.ValidationManager.State.VALID;
 import static org.briarproject.db.DatabaseConstants.DB_SETTINGS_NAMESPACE;
 import static org.briarproject.db.DatabaseConstants.DEVICE_ID_KEY;
 import static org.briarproject.db.DatabaseConstants.DEVICE_SETTINGS_NAMESPACE;
@@ -67,8 +67,8 @@ import static org.briarproject.db.ExponentialBackoff.calculateExpiry;
  */
 abstract class JdbcDatabase implements Database<Connection> {
 
-	private static final int SCHEMA_VERSION = 26;
-	private static final int MIN_SCHEMA_VERSION = 26;
+	private static final int SCHEMA_VERSION = 27;
+	private static final int MIN_SCHEMA_VERSION = 27;
 
 	private static final String CREATE_SETTINGS =
 			"CREATE TABLE settings"
@@ -155,8 +155,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	private static final String CREATE_MESSAGE_DEPENDENCIES =
 			"CREATE TABLE messageDependencies"
-					+ " (messageId HASH NOT NULL,"
+					+ " (groupId HASH NOT NULL,"
+					+ " messageId HASH NOT NULL,"
 					+ " dependencyId HASH NOT NULL," // Not a foreign key
+					+ " FOREIGN KEY (groupId)"
+					+ " REFERENCES groups (groupId)"
+					+ " ON DELETE CASCADE,"
 					+ " FOREIGN KEY (messageId)"
 					+ " REFERENCES messages (messageId)"
 					+ " ON DELETE CASCADE)";
@@ -609,16 +613,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	public void addMessageDependency(Connection txn, MessageId dependentId,
-			MessageId dependencyId) throws DbException {
+	public void addMessageDependency(Connection txn, GroupId g,
+			MessageId dependent, MessageId dependency) throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql =
-					"INSERT INTO messageDependencies (messageId, dependencyId)"
-							+ " VALUES (?, ?)";
+			String sql = "INSERT INTO messageDependencies"
+					+ " (groupId, messageId, dependencyId)"
+					+ " VALUES (?, ?, ?)";
 			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, dependentId.getBytes());
-			ps.setBytes(2, dependencyId.getBytes());
+			ps.setBytes(1, g.getBytes());
+			ps.setBytes(2, dependent.getBytes());
+			ps.setBytes(3, dependency.getBytes());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
@@ -1453,7 +1458,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT d.dependencyId, m.state, m.groupId"
+			String sql = "SELECT d.dependencyId, m.state, d.groupId, m.groupId"
 					+ " FROM messageDependencies AS d"
 					+ " LEFT OUTER JOIN messages AS m"
 					+ " ON d.dependencyId = m.messageId"
@@ -1463,13 +1468,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 			rs = ps.executeQuery();
 			Map<MessageId, State> dependencies = new HashMap<MessageId, State>();
 			while (rs.next()) {
-				MessageId messageId = new MessageId(rs.getBytes(1));
+				MessageId dependency = new MessageId(rs.getBytes(1));
 				State state = State.fromValue(rs.getInt(2));
-				if (state != UNKNOWN) {
-					// set dependency invalid if it is in a different group
-					if (!hasGroupId(txn, m, rs.getBytes(3))) state = INVALID;
+				if (rs.wasNull()) {
+					state = UNKNOWN; // Missing dependency
+				} else {
+					GroupId dependentGroupId = new GroupId(rs.getBytes(3));
+					GroupId dependencyGroupId = new GroupId(rs.getBytes(4));
+					if (!dependentGroupId.equals(dependencyGroupId))
+						state = INVALID; // Dependency in another group
 				}
-				dependencies.put(messageId, state);
+				dependencies.put(dependency, state);
 			}
 			rs.close();
 			ps.close();
@@ -1481,29 +1490,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private boolean hasGroupId(Connection txn, MessageId m, byte[] g)
-			throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT NULL FROM messages"
-					+ " WHERE messageId = ? AND groupId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setBytes(2, g);
-			rs = ps.executeQuery();
-			boolean same = rs.next();
-			if (rs.next()) throw new DbStateException();
-			rs.close();
-			ps.close();
-			return same;
-		} catch (SQLException e) {
-			tryToClose(rs);
-			tryToClose(ps);
-			throw new DbException(e);
-		}
-	}
-
 	public Map<MessageId, State> getMessageDependents(Connection txn,
 			MessageId m) throws DbException {
 		PreparedStatement ps = null;
@@ -1511,7 +1497,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			String sql = "SELECT d.messageId, m.state"
 					+ " FROM messageDependencies AS d"
-					+ " LEFT OUTER JOIN messages AS m"
+					+ " JOIN messages AS m"
 					+ " ON d.messageId = m.messageId"
 					+ " WHERE dependencyId = ?";
 			ps = txn.prepareStatement(sql);
@@ -1519,9 +1505,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 			rs = ps.executeQuery();
 			Map<MessageId, State> dependents = new HashMap<MessageId, State>();
 			while (rs.next()) {
-				MessageId messageId = new MessageId(rs.getBytes(1));
+				MessageId dependent = new MessageId(rs.getBytes(1));
 				State state = State.fromValue(rs.getInt(2));
-				dependents.put(messageId, state);
+				dependents.put(dependent, state);
 			}
 			rs.close();
 			ps.close();
@@ -1533,6 +1519,28 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	public State getMessageState(Connection txn, MessageId m)
+			throws DbException {
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT state FROM messages WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			rs = ps.executeQuery();
+			if (!rs.next()) throw new DbStateException();
+			State state = State.fromValue(rs.getInt(1));
+			if (rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
+			return state;
+		} catch (SQLException e) {
+			tryToClose(rs);
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
 	public Collection<MessageId> getMessagesToAck(Connection txn, ContactId c,
 			int maxMessages) throws DbException {
 		PreparedStatement ps = null;
@@ -1655,11 +1663,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		return getMessagesInState(txn, c, UNKNOWN);
 	}
 
-	public Collection<MessageId> getMessagesToDeliver(Connection txn,
-			ClientId c) throws DbException {
-		return getMessagesInState(txn, c, VALID);
-	}
-
 	public Collection<MessageId> getPendingMessages(Connection txn,
 			ClientId c) throws DbException {
 		return getMessagesInState(txn, c, PENDING);
@@ -1689,6 +1692,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Nullable
 	public byte[] getRawMessage(Connection txn, MessageId m)
 			throws DbException {
 		PreparedStatement ps = null;

briar-core/src/org/briarproject/forum/ForumManagerImpl.java

@@ -33,7 +33,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
@@ -49,9 +48,6 @@ import static org.briarproject.api.identity.Author.Status.ANONYMOUS;
 
 class ForumManagerImpl extends BdfIncomingMessageHook implements ForumManager {
 
-	private static final Logger LOG =
-			Logger.getLogger(ForumManagerImpl.class.getName());
-
 	static final ClientId CLIENT_ID = new ClientId(StringUtils.fromHexString(
 			"859a7be50dca035b64bd6902fb797097"
 					+ "795af837abbf8c16d750b3c2ccc186ea"));
@@ -133,7 +129,7 @@ class ForumManagerImpl extends BdfIncomingMessageHook implements ForumManager {
 			}
 			meta.put(KEY_LOCAL, true);
 			meta.put(KEY_READ, true);
-			clientHelper.addLocalMessage(p.getMessage(), CLIENT_ID, meta, true);
+			clientHelper.addLocalMessage(p.getMessage(), meta, true);
 		} catch (FormatException e) {
 			throw new RuntimeException(e);
 		}

briar-core/src/org/briarproject/forum/ForumPostValidator.java

@@ -101,7 +101,7 @@ class ForumPostValidator extends BdfMessageValidator {
 		}
 		// Return the metadata and dependencies
 		BdfDictionary meta = new BdfDictionary();
-		Collection<MessageId> dependencies = null;
+		Collection<MessageId> dependencies = Collections.emptyList();
 		meta.put("timestamp", m.getTimestamp());
 		if (parent != null) {
 			meta.put("parent", parent);

briar-core/src/org/briarproject/introduction/IntroduceeManager.java

@@ -177,8 +177,7 @@ class IntroduceeManager {
 		d.put(REMOTE_AUTHOR_IS_US, introducesOtherIdentity);
 
 		// save local state to database
-		clientHelper.addLocalMessage(txn, localMsg,
-				IntroductionManagerImpl.CLIENT_ID, d, false);
+		clientHelper.addLocalMessage(txn, localMsg, d, false);
 
 		return d;
 	}

briar-core/src/org/briarproject/introduction/IntroducerManager.java

@@ -98,9 +98,7 @@ class IntroducerManager {
 		d.put(AUTHOR_ID_2, c2.getAuthor().getId());
 
 		// save local state to database
-		clientHelper
-				.addLocalMessage(txn, m, IntroductionManagerImpl.CLIENT_ID, d,
-						false);
+		clientHelper.addLocalMessage(txn, m, d, false);
 
 		return d;
 	}

briar-core/src/org/briarproject/messaging/MessagingManagerImpl.java

@@ -117,7 +117,7 @@ class MessagingManagerImpl extends BdfIncomingMessageHook
 			meta.put("contentType", m.getContentType());
 			meta.put("local", true);
 			meta.put("read", true);
-			clientHelper.addLocalMessage(m.getMessage(), CLIENT_ID, meta, true);
+			clientHelper.addLocalMessage(m.getMessage(), meta, true);
 		} catch (FormatException e) {
 			throw new RuntimeException(e);
 		}

briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java

@@ -246,7 +246,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			meta.put("transportId", t.getString());
 			meta.put("version", version);
 			meta.put("local", local);
-			clientHelper.addLocalMessage(txn, m, CLIENT_ID, meta, shared);
+			clientHelper.addLocalMessage(txn, m, meta, shared);
 		} catch (FormatException e) {
 			throw new RuntimeException(e);
 		}

briar-core/src/org/briarproject/sharing/SharingManagerImpl.java

@@ -626,7 +626,7 @@ abstract class SharingManagerImpl<S extends Shareable, I extends Invitation, IS
 
 		// save local state to database
 		BdfDictionary d = s.toBdfDictionary();
-		clientHelper.addLocalMessage(txn, m, getClientId(), d, false);
+		clientHelper.addLocalMessage(txn, m, d, false);
 
 		return s;
 	}
@@ -652,7 +652,7 @@ abstract class SharingManagerImpl<S extends Shareable, I extends Invitation, IS
 
 		// save local state to database
 		BdfDictionary d = s.toBdfDictionary();
-		clientHelper.addLocalMessage(txn, m, getClientId(), d, false);
+		clientHelper.addLocalMessage(txn, m, d, false);
 
 		return s;
 	}

briar-core/src/org/briarproject/sync/ValidationManagerImpl.java

@@ -41,7 +41,6 @@ import static org.briarproject.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.api.sync.ValidationManager.State.DELIVERED;
 import static org.briarproject.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.api.sync.ValidationManager.State.PENDING;
-import static org.briarproject.api.sync.ValidationManager.State.VALID;
 
 class ValidationManagerImpl implements ValidationManager, Service,
 		EventListener {
@@ -71,8 +70,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	public void startService() {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		for (ClientId c : validators.keySet()) {
-			validateOutstandingMessages(c);
-			deliverOutstandingMessages(c);
+			validateOutstandingMessagesAsync(c);
+			deliverOutstandingMessagesAsync(c);
 		}
 	}
 
@@ -91,168 +90,156 @@ class ValidationManagerImpl implements ValidationManager, Service,
 		hooks.put(c, hook);
 	}
 
-	private void validateOutstandingMessages(final ClientId c) {
+	private void validateOutstandingMessagesAsync(final ClientId c) {
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				try {
-					Queue<MessageId> unvalidated = new LinkedList<MessageId>();
-					Transaction txn = db.startTransaction(true);
-					try {
-						unvalidated.addAll(db.getMessagesToValidate(txn, c));
-						txn.setComplete();
-					} finally {
-						db.endTransaction(txn);
-					}
-					validateNextMessage(unvalidated);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				validateOutstandingMessages(c);
 			}
 		});
 	}
 
-	private void validateNextMessage(final Queue<MessageId> unvalidated) {
+	private void validateOutstandingMessages(ClientId c) {
+		try {
+			Queue<MessageId> unvalidated = new LinkedList<MessageId>();
+			Transaction txn = db.startTransaction(true);
+			try {
+				unvalidated.addAll(db.getMessagesToValidate(txn, c));
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
+			}
+			validateNextMessageAsync(unvalidated);
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
+	private void validateNextMessageAsync(final Queue<MessageId> unvalidated) {
 		if (unvalidated.isEmpty()) return;
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				try {
-					Message m = null;
-					Group g = null;
-					Transaction txn = db.startTransaction(true);
-					try {
-						MessageId id = unvalidated.poll();
-						byte[] raw = db.getRawMessage(txn, id);
-						m = parseMessage(id, raw);
-						g = db.getGroup(txn, m.getGroupId());
-						txn.setComplete();
-					} catch (NoSuchMessageException e) {
-						LOG.info("Message removed before validation");
-						// Continue to next message
-					} catch (NoSuchGroupException e) {
-						LOG.info("Group removed before validation");
-						// Continue to next message
-					} finally {
-						if (!txn.isComplete()) txn.setComplete();
-						db.endTransaction(txn);
-					}
-					if (m != null && g != null) validateMessage(m, g);
-					validateNextMessage(unvalidated);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				validateNextMessage(unvalidated);
 			}
 		});
 	}
 
-	private void deliverOutstandingMessages(final ClientId c) {
+	private void validateNextMessage(Queue<MessageId> unvalidated) {
+		try {
+			Message m;
+			Group g;
+			Transaction txn = db.startTransaction(true);
+			try {
+				MessageId id = unvalidated.poll();
+				byte[] raw = db.getRawMessage(txn, id);
+				m = parseMessage(id, raw);
+				g = db.getGroup(txn, m.getGroupId());
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
+			}
+			validateMessageAsync(m, g);
+			validateNextMessageAsync(unvalidated);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Message removed before validation");
+			validateNextMessageAsync(unvalidated);
+		} catch (NoSuchGroupException e) {
+			LOG.info("Group removed before validation");
+			validateNextMessageAsync(unvalidated);
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
+	private void deliverOutstandingMessagesAsync(final ClientId c) {
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				try {
-					Queue<MessageId> validated = new LinkedList<MessageId>();
-					Queue<MessageId> pending = new LinkedList<MessageId>();
-					Transaction txn = db.startTransaction(true);
-					try {
-						validated.addAll(db.getMessagesToDeliver(txn, c));
-						pending.addAll(db.getPendingMessages(txn, c));
-						txn.setComplete();
-					} finally {
-						db.endTransaction(txn);
-					}
-					deliverNextMessage(validated);
-					deliverNextPendingMessage(pending);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				deliverOutstandingMessages(c);
 			}
 		});
 	}
 
-	private void deliverNextMessage(final Queue<MessageId> validated) {
-		if (validated.isEmpty()) return;
-		dbExecutor.execute(new Runnable() {
-			@Override
-			public void run() {
-				try {
-					Message m = null;
-					Group g = null;
-					Metadata meta = null;
-					Transaction txn = db.startTransaction(true);
-					try {
-						MessageId id = validated.poll();
-						byte[] raw = db.getRawMessage(txn, id);
-						m = parseMessage(id, raw);
-						g = db.getGroup(txn, m.getGroupId());
-						meta = db.getMessageMetadataForValidator(txn, id);
-						txn.setComplete();
-					} finally {
-						db.endTransaction(txn);
-					}
-					if (g != null) deliverMessage(m, g.getClientId(), meta);
-					deliverNextMessage(validated);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+	private void deliverOutstandingMessages(ClientId c) {
+		try {
+			Queue<MessageId> pending = new LinkedList<MessageId>();
+			Transaction txn = db.startTransaction(true);
+			try {
+				pending.addAll(db.getPendingMessages(txn, c));
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
 			}
-		});
+			deliverNextPendingMessageAsync(pending);
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
 	}
 
-	private void deliverNextPendingMessage(final Queue<MessageId> pending) {
+	private void deliverNextPendingMessageAsync(
+			final Queue<MessageId> pending) {
 		if (pending.isEmpty()) return;
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				Message m = null;
-				ClientId c = null;
-				try {
-					boolean allDelivered = true;
-					Metadata meta = null;
-					Transaction txn = db.startTransaction(true);
-					try {
-						MessageId id = pending.poll();
-						byte[] raw = db.getRawMessage(txn, id);
-						m = parseMessage(id, raw);
-						Group g = db.getGroup(txn, m.getGroupId());
-						c = g.getClientId();
-
-						// check if a dependency is invalid
-						Map<MessageId, State> states =
-								db.getMessageDependencies(txn, id);
-						for (Entry<MessageId, State> d : states.entrySet()) {
-							if (d.getValue() == INVALID) {
-								throw new InvalidMessageException(
-										"Invalid Dependency");
-							}
-							if (d.getValue() != DELIVERED) allDelivered = false;
-						}
-						if (allDelivered)
-							meta = db.getMessageMetadataForValidator(txn, id);
-						txn.setComplete();
-					} finally {
-						if (!txn.isComplete()) txn.setComplete();
-						db.endTransaction(txn);
-					}
-					if (c != null && allDelivered) deliverMessage(m, c, meta);
-					deliverNextPendingMessage(pending);
-				} catch(InvalidMessageException e) {
-					if (LOG.isLoggable(INFO))
-						LOG.log(INFO, e.toString(), e);
-					markMessageInvalid(m, c);
-					deliverNextPendingMessage(pending);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				deliverNextPendingMessage(pending);
 			}
 		});
 	}
 
+	private void deliverNextPendingMessage(Queue<MessageId> pending) {
+		try {
+			boolean anyInvalid = false, allDelivered = true;
+			Queue<MessageId> invalidate = null;
+			Transaction txn = db.startTransaction(false);
+			try {
+				MessageId id = pending.poll();
+				// Check if message is still pending
+				if (db.getMessageState(txn, id) == PENDING) {
+					// Check if dependencies are valid and delivered
+					Map<MessageId, State> states =
+							db.getMessageDependencies(txn, id);
+					for (Entry<MessageId, State> e : states.entrySet()) {
+						if (e.getValue() == INVALID) anyInvalid = true;
+						if (e.getValue() != DELIVERED) allDelivered = false;
+					}
+					if (anyInvalid) {
+						if (db.getMessageState(txn, id) != INVALID) {
+							invalidateMessage(txn, id);
+							invalidate = getDependentsToInvalidate(txn, id);
+						}
+					} else if (allDelivered) {
+						Message m = parseMessage(id, db.getRawMessage(txn, id));
+						Group g = db.getGroup(txn, m.getGroupId());
+						ClientId c = g.getClientId();
+						Metadata meta = db.getMessageMetadataForValidator(txn,
+								id);
+						if (deliverMessage(txn, m, c, meta)) {
+							pending.addAll(getPendingDependents(txn, id));
+						} else {
+							invalidate = getDependentsToInvalidate(txn, id);
+						}
+					}
+				}
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
+			}
+			if (invalidate != null) invalidateNextMessageAsync(invalidate);
+			deliverNextPendingMessageAsync(pending);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Message removed before delivery");
+			deliverNextPendingMessageAsync(pending);
+		} catch (NoSuchGroupException e) {
+			LOG.info("Group removed before delivery");
+			deliverNextPendingMessageAsync(pending);
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING))
+				LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
 	private Message parseMessage(MessageId id, byte[] raw) {
 		if (raw.length <= MESSAGE_HEADER_LENGTH)
 			throw new IllegalArgumentException();
@@ -262,199 +249,168 @@ class ValidationManagerImpl implements ValidationManager, Service,
 		return new Message(id, new GroupId(groupId), timestamp, raw);
 	}
 
-	private void validateMessage(final Message m, final Group g) {
+	private void validateMessageAsync(final Message m, final Group g) {
 		cryptoExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				MessageValidator v = validators.get(g.getClientId());
-				if (v == null) {
-					LOG.warning("No validator");
-				} else {
-					try {
-						MessageContext context = v.validateMessage(m, g);
-						storeMessageContext(m, g.getClientId(), context);
-					} catch (InvalidMessageException e) {
-						if (LOG.isLoggable(INFO))
-							LOG.log(INFO, e.toString(), e);
-						markMessageInvalid(m, g.getClientId());
-					}
-				}
+				validateMessage(m, g);
 			}
 		});
 	}
 
-	private void storeMessageContext(final Message m, final ClientId c,
+	private void validateMessage(Message m, Group g) {
+		MessageValidator v = validators.get(g.getClientId());
+		if (v == null) {
+			LOG.warning("No validator");
+		} else {
+			try {
+				MessageContext context = v.validateMessage(m, g);
+				storeMessageContextAsync(m, g.getClientId(), context);
+			} catch (InvalidMessageException e) {
+				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
+				Queue<MessageId> invalidate = new LinkedList<MessageId>();
+				invalidate.add(m.getId());
+				invalidateNextMessageAsync(invalidate);
+			}
+		}
+	}
+
+	private void storeMessageContextAsync(final Message m, final ClientId c,
 			final MessageContext result) {
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				try {
-					State newState = null;
-					Metadata meta = null;
-					Transaction txn = db.startTransaction(false);
-					try {
-						// store dependencies
-						Collection<MessageId> dependencies =
-								result.getDependencies();
-						if (dependencies != null && dependencies.size() > 0) {
-							db.addMessageDependencies(txn, m, dependencies);
-						}
-						// check if a dependency is invalid
-						// and if all dependencies have been delivered
-						Map<MessageId, State> states =
-								db.getMessageDependencies(txn, m.getId());
-						newState = VALID;
-						for (Entry<MessageId, State> d : states.entrySet()) {
-							if (d.getValue() == INVALID) {
-								throw new InvalidMessageException(
-										"Dependency Invalid");
-							}
-							if (d.getValue() != DELIVERED) {
-								newState = PENDING;
-								LOG.info("depend. undelivered, set to PENDING");
-								break;
-							}
-						}
-						// save metadata and new message state
-						meta = result.getMetadata();
-						db.mergeMessageMetadata(txn, m.getId(), meta);
-						db.setMessageState(txn, m, c, newState);
-						txn.setComplete();
-					} finally {
-						if (!txn.isComplete()) txn.setComplete();
-						db.endTransaction(txn);
-					}
-					// deliver message if valid
-					if (newState == VALID) {
-						deliverMessage(m, c, meta);
-					}
-				} catch (InvalidMessageException e) {
-					if (LOG.isLoggable(INFO))
-						LOG.log(INFO, e.toString(), e);
-					markMessageInvalid(m, c);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				storeMessageContext(m, c, result);
 			}
 		});
 	}
 
-	private void deliverMessage(final Message m, final ClientId c,
-			final Metadata meta) {
+	private void storeMessageContext(Message m, ClientId c,
+			MessageContext result) {
+		try {
+			MessageId id = m.getId();
+			boolean anyInvalid = false, allDelivered = true;
+			Queue<MessageId> invalidate = null;
+			Queue<MessageId> pending = null;
+			Transaction txn = db.startTransaction(false);
+			try {
+				// Check if message has any dependencies
+				Collection<MessageId> dependencies = result.getDependencies();
+				if (!dependencies.isEmpty()) {
+					db.addMessageDependencies(txn, m, dependencies);
+					// Check if dependencies are valid and delivered
+					Map<MessageId, State> states =
+							db.getMessageDependencies(txn, id);
+					for (Entry<MessageId, State> e : states.entrySet()) {
+						if (e.getValue() == INVALID) anyInvalid = true;
+						if (e.getValue() != DELIVERED) allDelivered = false;
+					}
+				}
+				if (anyInvalid) {
+					if (db.getMessageState(txn, id) != INVALID) {
+						invalidateMessage(txn, id);
+						invalidate = getDependentsToInvalidate(txn, id);
+					}
+				} else {
+					Metadata meta = result.getMetadata();
+					db.mergeMessageMetadata(txn, id, meta);
+					if (allDelivered) {
+						if (deliverMessage(txn, m, c, meta)) {
+							pending = getPendingDependents(txn, id);
+						} else {
+							invalidate = getDependentsToInvalidate(txn, id);
+						}
+					} else {
+						db.setMessageState(txn, id, PENDING);
+					}
+				}
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
+			}
+			if (invalidate != null) invalidateNextMessageAsync(invalidate);
+			if (pending != null) deliverNextPendingMessageAsync(pending);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Message removed during validation");
+		} catch (NoSuchGroupException e) {
+			LOG.info("Group removed during validation");
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
+	private boolean deliverMessage(Transaction txn, Message m, ClientId c,
+			Metadata meta) throws DbException {
+		IncomingMessageHook hook = hooks.get(c);
+		if (hook == null) throw new DbException();
+		hook.incomingMessage(txn, m, meta);
+		// TODO: Find a better way for clients to signal validity, #643
+		if (db.getRawMessage(txn, m.getId()) == null) {
+			db.setMessageState(txn, m.getId(), INVALID);
+			return false;
+		} else {
+			db.setMessageState(txn, m.getId(), DELIVERED);
+			return true;
+		}
+	}
+
+	private Queue<MessageId> getPendingDependents(Transaction txn, MessageId m)
+			throws DbException {
+		Queue<MessageId> pending = new LinkedList<MessageId>();
+		Map<MessageId, State> states = db.getMessageDependents(txn, m);
+		for (Entry<MessageId, State> e : states.entrySet()) {
+			if (e.getValue() == PENDING) pending.add(e.getKey());
+		}
+		return pending;
+	}
+
+	private void invalidateNextMessageAsync(final Queue<MessageId> invalidate) {
+		if (invalidate.isEmpty()) return;
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				try {
-					Queue<MessageId> pending = new LinkedList<MessageId>();
-					Transaction txn = db.startTransaction(false);
-					try {
-						IncomingMessageHook hook = hooks.get(c);
-						if (hook != null)
-							hook.incomingMessage(txn, m, meta);
-
-						// check if message was deleted by client
-						if (db.getRawMessage(txn, m.getId()) == null) {
-							throw new InvalidMessageException(
-									"Deleted by Client");
-						}
-						db.setMessageState(txn, m, c, DELIVERED);
-
-						// deliver pending dependents
-						Map<MessageId, State> dependents =
-								db.getMessageDependents(txn, m.getId());
-						for (Entry<MessageId, State> i : dependents
-								.entrySet()) {
-							if (i.getValue() != PENDING) continue;
-
-							// check that all dependencies are delivered
-							Map<MessageId, State> dependencies =
-									db.getMessageDependencies(txn, i.getKey());
-							for (Entry<MessageId, State> j : dependencies
-									.entrySet()) {
-								if (j.getValue() != DELIVERED) return;
-							}
-							pending.add(i.getKey());
-						}
-						txn.setComplete();
-					} finally {
-						if (!txn.isComplete()) txn.setComplete();
-						db.endTransaction(txn);
-					}
-					deliverNextMessage(pending);
-				} catch (InvalidMessageException e) {
-					if (LOG.isLoggable(INFO))
-						LOG.log(INFO, e.toString(), e);
-					markMessageInvalid(m, c);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				invalidateNextMessage(invalidate);
 			}
 		});
 	}
 
-	private void markMessageInvalid(final Message m, final ClientId c) {
-		dbExecutor.execute(new Runnable() {
-			@Override
-			public void run() {
-				try {
-					Queue<MessageId> invalid = new LinkedList<MessageId>();
-					Transaction txn = db.startTransaction(false);
-					try {
-						Map<MessageId, State> dependents =
-								db.getMessageDependents(txn, m.getId());
-						db.setMessageState(txn, m, c, INVALID);
-						db.deleteMessage(txn, m.getId());
-						db.deleteMessageMetadata(txn, m.getId());
-
-						// recursively invalidate all messages that depend on m
-						// TODO check that cycles are properly taken care of
-						for (Entry<MessageId, State> i : dependents
-								.entrySet()) {
-							if (i.getValue() != INVALID) {
-								invalid.add(i.getKey());
-							}
-						}
-						txn.setComplete();
-					} finally {
-						db.endTransaction(txn);
-					}
-					markNextMessageInvalid(invalid);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
+	private void invalidateNextMessage(Queue<MessageId> invalidate) {
+		try {
+			Transaction txn = db.startTransaction(false);
+			try {
+				MessageId id = invalidate.poll();
+				if (db.getMessageState(txn, id) != INVALID) {
+					invalidateMessage(txn, id);
+					invalidate.addAll(getDependentsToInvalidate(txn, id));
 				}
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
 			}
-		});
+			invalidateNextMessageAsync(invalidate);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Message removed before invalidation");
+			invalidateNextMessageAsync(invalidate);
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
 	}
 
-	private void markNextMessageInvalid(final Queue<MessageId> invalid) {
-		if (invalid.isEmpty()) return;
-		dbExecutor.execute(new Runnable() {
-			@Override
-			public void run() {
-				try {
-					Message m = null;
-					Group g = null;
-					Transaction txn = db.startTransaction(true);
-					try {
-						MessageId id = invalid.poll();
-						byte[] raw = db.getRawMessage(txn, id);
-						m = parseMessage(id, raw);
-						g = db.getGroup(txn, m.getGroupId());
-						txn.setComplete();
-					} finally {
-						db.endTransaction(txn);
-					}
-					if (g != null) markMessageInvalid(m, g.getClientId());
-					markNextMessageInvalid(invalid);
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
-			}
-		});
+	private void invalidateMessage(Transaction txn, MessageId m)
+			throws DbException {
+		db.setMessageState(txn, m, INVALID);
+		db.deleteMessage(txn, m);
+		db.deleteMessageMetadata(txn, m);
+	}
+
+	private Queue<MessageId> getDependentsToInvalidate(Transaction txn,
+			MessageId m) throws DbException {
+		Queue<MessageId> invalidate = new LinkedList<MessageId>();
+		Map<MessageId, State> states = db.getMessageDependents(txn, m);
+		for (Entry<MessageId, State> e : states.entrySet()) {
+			if (e.getValue() != INVALID) invalidate.add(e.getKey());
+		}
+		return invalidate;
 	}
 
 	@Override
@@ -462,31 +418,35 @@ class ValidationManagerImpl implements ValidationManager, Service,
 		if (e instanceof MessageAddedEvent) {
 			// Validate the message if it wasn't created locally
 			MessageAddedEvent m = (MessageAddedEvent) e;
-			if (m.getContactId() != null) loadGroupAndValidate(m.getMessage());
+			if (m.getContactId() != null)
+				loadGroupAndValidateAsync(m.getMessage());
 		}
 	}
 
-	private void loadGroupAndValidate(final Message m) {
+	private void loadGroupAndValidateAsync(final Message m) {
 		dbExecutor.execute(new Runnable() {
 			@Override
 			public void run() {
-				try {
-					Group g;
-					Transaction txn = db.startTransaction(true);
-					try {
-						g = db.getGroup(txn, m.getGroupId());
-						txn.setComplete();
-					} finally {
-						db.endTransaction(txn);
-					}
-					validateMessage(m, g);
-				} catch (NoSuchGroupException e) {
-					LOG.info("Group removed before validation");
-				} catch (DbException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
+				loadGroupAndValidate(m);
 			}
 		});
 	}
+
+	private void loadGroupAndValidate(final Message m) {
+		try {
+			Group g;
+			Transaction txn = db.startTransaction(true);
+			try {
+				g = db.getGroup(txn, m.getGroupId());
+				txn.setComplete();
+			} finally {
+				db.endTransaction(txn);
+			}
+			validateMessageAsync(m, g);
+		} catch (NoSuchGroupException e) {
+			LOG.info("Group removed before validation");
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
 }