Merge branch '541-faster-retransmission-eta' into 'master'

Allow retransmission if it will result in faster delivery

Closes #541

See merge request briar/briar!908

bramble-api/src/test/java/org/briarproject/bramble/test/ArrayClock.java

@@ -0,0 +1,23 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.system.Clock;
+
+public class ArrayClock implements Clock {
+
+	private final long[] times;
+	private int index = 0;
+
+	public ArrayClock(long... times) {
+		this.times = times;
+	}
+
+	@Override
+	public long currentTimeMillis() {
+		return times[index++];
+	}
+
+	@Override
+	public void sleep(long milliseconds) throws InterruptedException {
+		Thread.sleep(milliseconds);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -421,7 +421,7 @@ interface Database<T> {
 	 * Read-only.
 	 */
 	Collection<MessageId> getMessagesToOffer(T txn, ContactId c,
-			int maxMessages) throws DbException;
+			int maxMessages, int maxLatency) throws DbException;
 
 	/**
 	 * Returns the IDs of some messages that are eligible to be requested from
@@ -438,8 +438,8 @@ interface Database<T> {
 	 * <p/>
 	 * Read-only.
 	 */
-	Collection<MessageId> getMessagesToSend(T txn, ContactId c, int maxLength)
+	Collection<MessageId> getMessagesToSend(T txn, ContactId c, int maxLength,
-			throws DbException;
+			int maxLatency) throws DbException;
 
 	/**
 	 * Returns the IDs of any messages that need to be validated.
@@ -482,7 +482,7 @@ interface Database<T> {
 	 * Read-only.
 	 */
 	Collection<MessageId> getRequestedMessagesToSend(T txn, ContactId c,
-			int maxLength) throws DbException;
+			int maxLength, int maxLatency) throws DbException;
 
 	/**
 	 * Returns all settings in the given namespace.
@@ -647,11 +647,11 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Updates the transmission count and expiry time of the given message
+	 * Updates the transmission count, expiry time and estimated time of arrival
-	 * with respect to the given contact, using the latency of the transport
+	 * of the given message with respect to the given contact, using the latency
-	 * over which it was sent.
+	 * of the transport over which it was sent.
 	 */
-	void updateExpiryTime(T txn, ContactId c, MessageId m, int maxLatency)
+	void updateExpiryTimeAndEta(T txn, ContactId c, MessageId m, int maxLatency)
 			throws DbException;
 
 	/**

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -313,11 +313,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids = db.getMessagesToSend(txn, c, maxLength);
+		Collection<MessageId> ids =
+				db.getMessagesToSend(txn, c, maxLength, maxLatency);
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
 			messages.add(db.getMessage(txn, m));
-			db.updateExpiryTime(txn, c, m, maxLatency);
+			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
 		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
@@ -333,9 +334,11 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids = db.getMessagesToOffer(txn, c, maxMessages);
+		Collection<MessageId> ids =
+				db.getMessagesToOffer(txn, c, maxMessages, maxLatency);
 		if (ids.isEmpty()) return null;
-		for (MessageId m : ids) db.updateExpiryTime(txn, c, m, maxLatency);
+		for (MessageId m : ids)
+			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		return new Offer(ids);
 	}
 
@@ -362,12 +365,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids = db.getRequestedMessagesToSend(txn, c,
+		Collection<MessageId> ids =
-				maxLength);
+				db.getRequestedMessagesToSend(txn, c, maxLength, maxLatency);
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
 			messages.add(db.getMessage(txn, m));
-			db.updateExpiryTime(txn, c, m, maxLatency);
+			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
 		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
@@ -855,7 +858,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (!db.containsMessage(txn, m))
 			throw new NoSuchMessageException();
 		if (db.getMessageState(txn, m) != DELIVERED)
-			throw new IllegalArgumentException("Shared undelivered message");
+			throw new IllegalArgumentException(
+					"Shared undelivered message");
 		db.setMessageShared(txn, m);
 		transaction.attach(new MessageSharedEvent(m));
 	}
@@ -881,7 +885,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchMessageException();
 		State dependentState = db.getMessageState(txn, dependent.getId());
 		for (MessageId dependency : dependencies) {
-			db.addMessageDependency(txn, dependent, dependency, dependentState);
+			db.addMessageDependency(txn, dependent, dependency,
+					dependentState);
 		}
 	}
 
@@ -913,7 +918,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		for (KeySet ks : keys) {
 			TransportId t = ks.getTransportKeys().getTransportId();
-			if (db.containsTransport(txn, t)) db.updateTransportKeys(txn, ks);
+			if (db.containsTransport(txn, t))
+				db.updateTransportKeys(txn, ks);
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -38,6 +38,7 @@ import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
@@ -55,7 +56,6 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 import static java.sql.Types.INTEGER;
-import static java.util.Collections.singletonList;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
@@ -79,7 +79,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 39;
+	static final int CODE_SCHEMA_VERSION = 40;
 
 	// Rotation period offsets for incoming transport keys
 	private static final int OFFSET_PREV = -1;
@@ -219,6 +219,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " requested BOOLEAN NOT NULL,"
 					+ " expiry BIGINT NOT NULL,"
 					+ " txCount INT NOT NULL,"
+					+ " eta BIGINT NOT NULL,"
 					+ " PRIMARY KEY (messageId, contactId),"
 					+ " FOREIGN KEY (messageId)"
 					+ " REFERENCES messages (messageId)"
@@ -397,7 +398,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
 	List<Migration<Connection>> getMigrations() {
-		return singletonList(new Migration38_39());
+		return Arrays.asList(new Migration38_39(), new Migration39_40());
 	}
 
 	private void storeSchemaVersion(Connection txn, int version)
@@ -805,8 +806,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			String sql = "INSERT INTO statuses (messageId, contactId, groupId,"
 					+ " timestamp, length, state, groupShared, messageShared,"
-					+ " deleted, ack, seen, requested, expiry, txCount)"
+					+ " deleted, ack, seen, requested, expiry, txCount, eta)"
-					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, FALSE, 0, 0)";
+					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, FALSE, 0, 0,"
+					+ " 0)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			ps.setInt(2, c.getInt());
@@ -1869,8 +1871,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	@Override
 	public Collection<MessageId> getMessagesToOffer(Connection txn,
-			ContactId c, int maxMessages) throws DbException {
+			ContactId c, int maxMessages, int maxLatency) throws DbException {
 		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -1879,13 +1882,14 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " AND groupShared = TRUE AND messageShared = TRUE"
 					+ " AND deleted = FALSE"
 					+ " AND seen = FALSE AND requested = FALSE"
-					+ " AND expiry < ?"
+					+ " AND (expiry < ? OR eta > ?)"
 					+ " ORDER BY timestamp LIMIT ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, DELIVERED.getValue());
 			ps.setLong(3, now);
-			ps.setInt(4, maxMessages);
+			ps.setLong(4, eta);
+			ps.setInt(5, maxMessages);
 			rs = ps.executeQuery();
 			List<MessageId> ids = new ArrayList<>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
@@ -1926,8 +1930,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	@Override
 	public Collection<MessageId> getMessagesToSend(Connection txn, ContactId c,
-			int maxLength) throws DbException {
+			int maxLength, int maxLatency) throws DbException {
 		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -1936,12 +1941,13 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " AND groupShared = TRUE AND messageShared = TRUE"
 					+ " AND deleted = FALSE"
 					+ " AND seen = FALSE"
-					+ " AND expiry < ?"
+					+ " AND (expiry < ? OR eta > ?)"
 					+ " ORDER BY timestamp";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, DELIVERED.getValue());
 			ps.setLong(3, now);
+			ps.setLong(4, eta);
 			rs = ps.executeQuery();
 			List<MessageId> ids = new ArrayList<>();
 			int total = 0;
@@ -2055,8 +2061,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	@Override
 	public Collection<MessageId> getRequestedMessagesToSend(Connection txn,
-			ContactId c, int maxLength) throws DbException {
+			ContactId c, int maxLength, int maxLatency) throws DbException {
 		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -2065,12 +2072,13 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " AND groupShared = TRUE AND messageShared = TRUE"
 					+ " AND deleted = FALSE"
 					+ " AND seen = FALSE AND requested = TRUE"
-					+ " AND expiry < ?"
+					+ " AND (expiry < ? OR eta > ?)"
 					+ " ORDER BY timestamp";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, DELIVERED.getValue());
 			ps.setLong(3, now);
+			ps.setLong(4, eta);
 			rs = ps.executeQuery();
 			List<MessageId> ids = new ArrayList<>();
 			int total = 0;
@@ -2881,7 +2889,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void updateExpiryTime(Connection txn, ContactId c, MessageId m,
+	public void updateExpiryTimeAndEta(Connection txn, ContactId c, MessageId m,
 			int maxLatency) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
@@ -2897,13 +2905,16 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
-			sql = "UPDATE statuses SET expiry = ?, txCount = txCount + 1"
+			sql = "UPDATE statuses"
+					+ " SET expiry = ?, txCount = txCount + 1, eta = ?"
 					+ " WHERE messageId = ? AND contactId = ?";
 			ps = txn.prepareStatement(sql);
 			long now = clock.currentTimeMillis();
+			long eta = now + maxLatency;
 			ps.setLong(1, calculateExpiry(now, maxLatency, txCount));
-			ps.setBytes(2, m.getBytes());
+			ps.setLong(2, eta);
-			ps.setInt(3, c.getInt());
+			ps.setBytes(3, m.getBytes());
+			ps.setInt(4, c.getInt());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();

bramble-core/src/main/java/org/briarproject/bramble/db/Migration39_40.java

@@ -0,0 +1,54 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.db.DbException;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+class Migration39_40 implements Migration<Connection> {
+
+	private static final Logger LOG =
+			Logger.getLogger(Migration39_40.class.getName());
+
+	@Override
+	public int getStartVersion() {
+		return 39;
+	}
+
+	@Override
+	public int getEndVersion() {
+		return 40;
+	}
+
+	@Override
+	public void migrate(Connection txn) throws DbException {
+		Statement s = null;
+		try {
+			s = txn.createStatement();
+			s.execute("ALTER TABLE statuses"
+					+ " ADD eta BIGINT");
+			s.execute("UPDATE statuses SET eta = 0");
+			s.execute("ALTER TABLE statuses"
+					+ " ALTER COLUMN eta"
+					+ " SET NOT NULL");
+		} catch (SQLException e) {
+			tryToClose(s);
+			throw new DbException(e);
+		}
+	}
+
+	private void tryToClose(@Nullable Statement s) {
+		try {
+			if (s != null) s.close();
+		} catch (SQLException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/crypto/ScryptKdfTest.java

@@ -11,6 +11,8 @@ import java.util.HashSet;
 import java.util.Set;
 
 import static junit.framework.TestCase.assertTrue;
+
+import org.briarproject.bramble.test.ArrayClock;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertEquals;
@@ -74,24 +76,4 @@ public class ScryptKdfTest extends BrambleTestCase {
 		PasswordBasedKdf kdf = new ScryptKdf(clock);
 		assertEquals(256, kdf.chooseCostParameter());
 	}
-
-	private static class ArrayClock implements Clock {
-
-		private final long[] times;
-		private int index = 0;
-
-		private ArrayClock(long... times) {
-			this.times = times;
-		}
-
-		@Override
-		public long currentTimeMillis() {
-			return times[index++];
-		}
-
-		@Override
-		public void sleep(long milliseconds) throws InterruptedException {
-			Thread.sleep(milliseconds);
-		}
-	}
 }

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseComponentImplTest.java

@@ -871,15 +871,15 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
 			oneOf(database).getMessagesToSend(txn, contactId,
-					MAX_MESSAGE_LENGTH * 2);
+					MAX_MESSAGE_LENGTH * 2, maxLatency);
 			will(returnValue(ids));
 			oneOf(database).getMessage(txn, messageId);
 			will(returnValue(message));
-			oneOf(database).updateExpiryTime(txn, contactId, messageId,
+			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId,
 					maxLatency);
 			oneOf(database).getMessage(txn, messageId1);
 			will(returnValue(message1));
-			oneOf(database).updateExpiryTime(txn, contactId, messageId1,
+			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId1,
 					maxLatency);
 			oneOf(database).lowerRequestedFlag(txn, contactId, ids);
 			oneOf(database).commitTransaction(txn);
@@ -907,11 +907,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			will(returnValue(txn));
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
-			oneOf(database).getMessagesToOffer(txn, contactId, 123);
+			oneOf(database).getMessagesToOffer(txn, contactId, 123, maxLatency);
 			will(returnValue(ids));
-			oneOf(database).updateExpiryTime(txn, contactId, messageId,
+			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId,
 					maxLatency);
-			oneOf(database).updateExpiryTime(txn, contactId, messageId1,
+			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId1,
 					maxLatency);
 			oneOf(database).commitTransaction(txn);
 		}});
@@ -967,15 +967,15 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
 			oneOf(database).getRequestedMessagesToSend(txn, contactId,
-					MAX_MESSAGE_LENGTH * 2);
+					MAX_MESSAGE_LENGTH * 2, maxLatency);
 			will(returnValue(ids));
 			oneOf(database).getMessage(txn, messageId);
 			will(returnValue(message));
-			oneOf(database).updateExpiryTime(txn, contactId, messageId,
+			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId,
 					maxLatency);
 			oneOf(database).getMessage(txn, messageId1);
 			will(returnValue(message1));
-			oneOf(database).updateExpiryTime(txn, contactId, messageId1,
+			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId1,
 					maxLatency);
 			oneOf(database).lowerRequestedFlag(txn, contactId, ids);
 			oneOf(database).commitTransaction(txn);

bramble-core/src/test/java/org/briarproject/bramble/db/DatabasePerformanceTest.java

@@ -96,6 +96,9 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 	 */
 	private static final int STEADY_STATE_BLOCKS = 5;
 
+	// All our transports use a maximum latency of 30 seconds
+	private static final int MAX_LATENCY = 30 * 1000;
+
 	protected final File testDir = getTestDirectory();
 	private final File resultsFile = new File(getTestName() + ".tsv");
 	protected final Random random = new Random();
@@ -448,7 +451,7 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		benchmark(name, db -> {
 			Connection txn = db.startTransaction();
 			db.getMessagesToOffer(txn, pickRandom(contacts).getId(),
-					MAX_MESSAGE_IDS);
+					MAX_MESSAGE_IDS, MAX_LATENCY);
 			db.commitTransaction(txn);
 		});
 	}
@@ -470,7 +473,7 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		benchmark(name, db -> {
 			Connection txn = db.startTransaction();
 			db.getMessagesToSend(txn, pickRandom(contacts).getId(),
-					MAX_MESSAGE_IDS);
+					MAX_MESSAGE_IDS, MAX_LATENCY);
 			db.commitTransaction(txn);
 		});
 	}
@@ -521,7 +524,7 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		benchmark(name, db -> {
 			Connection txn = db.startTransaction();
 			db.getRequestedMessagesToSend(txn, pickRandom(contacts).getId(),
-					MAX_MESSAGE_IDS);
+					MAX_MESSAGE_IDS, MAX_LATENCY);
 			db.commitTransaction(txn);
 		});
 	}

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -26,6 +26,7 @@ import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
 import org.briarproject.bramble.system.SystemClock;
+import org.briarproject.bramble.test.ArrayClock;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestDatabaseConfig;
 import org.briarproject.bramble.test.TestMessageFactory;
@@ -60,6 +61,7 @@ import static org.briarproject.bramble.api.sync.ValidationManager.State.DELIVERE
 import static org.briarproject.bramble.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
+import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
 import static org.briarproject.bramble.test.TestUtils.getClientId;
 import static org.briarproject.bramble.test.TestUtils.getGroup;
@@ -82,6 +84,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 	private static final int ONE_MEGABYTE = 1024 * 1024;
 	private static final int MAX_SIZE = 5 * ONE_MEGABYTE;
+	// All our transports use a maximum latency of 30 seconds
+	private static final int MAX_LATENCY = 30 * 1000;
+
 
 	private final SecretKey key = getSecretKey();
 	private final File testDir = getTestDirectory();
@@ -199,16 +204,16 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The contact has not seen the message, so it should be sendable
 		Collection<MessageId> ids =
-				db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+				db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
 		// Changing the status to seen = true should make the message unsendable
 		db.raiseSeenFlag(txn, contactId, messageId);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		db.commitTransaction(txn);
@@ -230,30 +235,30 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The message has not been validated, so it should not be sendable
 		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
-				ONE_MEGABYTE);
+				ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Marking the message delivered should make it sendable
 		db.setMessageState(txn, messageId, DELIVERED);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
 		// Marking the message invalid should make it unsendable
 		db.setMessageState(txn, messageId, INVALID);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Marking the message pending should make it unsendable
 		db.setMessageState(txn, messageId, PENDING);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		db.commitTransaction(txn);
@@ -274,37 +279,37 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The group is invisible, so the message should not be sendable
 		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
-				ONE_MEGABYTE);
+				ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Making the group visible should not make the message sendable
 		db.addGroupVisibility(txn, contactId, groupId, false);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Sharing the group should make the message sendable
 		db.setGroupVisibility(txn, contactId, groupId, true);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
 		// Unsharing the group should make the message unsendable
 		db.setGroupVisibility(txn, contactId, groupId, false);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Making the group invisible should make the message unsendable
 		db.removeGroupVisibility(txn, contactId, groupId);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		db.commitTransaction(txn);
@@ -326,16 +331,16 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The message is not shared, so it should not be sendable
 		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
-				ONE_MEGABYTE);
+				ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Sharing the message should make it sendable
 		db.setMessageShared(txn, messageId);
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
 		db.commitTransaction(txn);
@@ -356,12 +361,13 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message, DELIVERED, true, null);
 
 		// The message is sendable, but too large to send
-		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
+		Collection<MessageId> ids =
-				message.getRawLength() - 1);
+				db.getMessagesToSend(txn, contactId, message.getRawLength() - 1,
+						MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-
 		// The message is just the right size to send
-		ids = db.getMessagesToSend(txn, contactId, message.getRawLength());
+		ids = db.getMessagesToSend(txn, contactId, message.getRawLength(),
+				MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
 		db.commitTransaction(txn);
@@ -424,19 +430,19 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Retrieve the message from the database and mark it as sent
 		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
-				ONE_MEGABYTE);
+				ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
-		db.updateExpiryTime(txn, contactId, messageId, Integer.MAX_VALUE);
+		db.updateExpiryTimeAndEta(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should no longer be sendable
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Pretend that the message was acked
 		db.raiseSeenFlag(txn, contactId, messageId);
 
 		// The message still should not be sendable
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		db.commitTransaction(txn);
@@ -1517,7 +1523,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertFalse(status.isSeen());
 
 		// Pretend the message was sent to the contact
-		db.updateExpiryTime(txn, contactId, messageId, Integer.MAX_VALUE);
+		db.updateExpiryTimeAndEta(txn, contactId, messageId, Integer.MAX_VALUE);
 
 		// The message should be sent but not seen
 		status = db.getMessageStatus(txn, contactId, messageId);
@@ -1636,9 +1642,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The message should be sendable
 		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
-				ONE_MEGABYTE);
+				ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 
 		// The message should be available
@@ -1655,9 +1661,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertTrue(db.containsVisibleMessage(txn, contactId, messageId));
 
 		// The message should not be sendable
-		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE);
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
-		ids = db.getMessagesToOffer(txn, contactId, 100);
+		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
 
 		// Requesting the message should throw an exception
@@ -1761,12 +1767,12 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Update the message's expiry time as though we sent it - now the
 		// message should be sendable after one round-trip
-		db.updateExpiryTime(txn, contactId, messageId, 1000);
+		db.updateExpiryTimeAndEta(txn, contactId, messageId, 1000);
 		assertEquals(now + 2000, db.getNextSendTime(txn, contactId));
 
 		// Update the message's expiry time again - now it should be sendable
 		// after two round-trips
-		db.updateExpiryTime(txn, contactId, messageId, 1000);
+		db.updateExpiryTimeAndEta(txn, contactId, messageId, 1000);
 		assertEquals(now + 4000, db.getNextSendTime(txn, contactId));
 
 		// Delete the message - there should be no messages to send
@@ -1809,6 +1815,103 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
+	@Test
+	public void testMessageRetransmission() throws Exception {
+		long now = System.currentTimeMillis();
+		long steps[] = {now, now, now + MAX_LATENCY * 2,
+				now + MAX_LATENCY * 2 + 1};
+		Database<Connection> db =
+				open(false, new TestMessageFactory(), new ArrayClock(steps));
+		Connection txn = db.startTransaction();
+
+		// Add a contact, a shared group and a shared message
+		db.addLocalAuthor(txn, localAuthor);
+		assertEquals(contactId, db.addContact(txn, author, localAuthor.getId(),
+				true, true));
+		db.addGroup(txn, group);
+		db.addGroupVisibility(txn, contactId, groupId, true);
+		db.addMessage(txn, message, DELIVERED, true, null);
+
+		// Time: now
+		// Retrieve the message from the database
+		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
+				ONE_MEGABYTE, MAX_LATENCY);
+		assertEquals(singletonList(messageId), ids);
+
+		// Time: now
+		// Mark the message as sent
+		db.updateExpiryTimeAndEta(txn, contactId, messageId, MAX_LATENCY);
+
+		// The message should expire after 2 * MAX_LATENCY
+		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+
+		// Time: now + MAX_LATENCY * 2
+		// The message should not yet be sendable
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
+		assertTrue(ids.isEmpty());
+
+		// Time: now + MAX_LATENCY * 2 + 1
+		// The message should have expired and should now be sendable
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
+		assertEquals(singletonList(messageId), ids);
+
+		db.commitTransaction(txn);
+		db.close();
+	}
+
+
+	@Test
+	public void testFasterMessageRetransmission() throws Exception {
+		long now = System.currentTimeMillis();
+		long steps[] = {now, now, now, now, now + 1};
+		Database<Connection> db =
+				open(false, new TestMessageFactory(), new ArrayClock(steps));
+		Connection txn = db.startTransaction();
+
+		// Add a contact, a shared group and a shared message
+		db.addLocalAuthor(txn, localAuthor);
+		assertEquals(contactId, db.addContact(txn, author, localAuthor.getId(),
+				true, true));
+		db.addGroup(txn, group);
+		db.addGroupVisibility(txn, contactId, groupId, true);
+		db.addMessage(txn, message, DELIVERED, true, null);
+
+		// Time: now
+		// Retrieve the message from the database
+		Collection<MessageId> ids = db.getMessagesToSend(txn, contactId,
+				ONE_MEGABYTE, MAX_LATENCY);
+		assertEquals(singletonList(messageId), ids);
+
+		// Time: now
+		// Mark the message as sent
+		db.updateExpiryTimeAndEta(txn, contactId, messageId, MAX_LATENCY);
+
+		// The message should expire after 2 * MAX_LATENCY
+		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+
+		// Time: now
+		// The message should not be sendable via the same transport
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
+		assertTrue(ids.isEmpty());
+
+		// Time: now
+		// The message should be sendable via a transport with a faster ETA
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE,
+				MAX_LATENCY - 1);
+		assertEquals(singletonList(messageId), ids);
+
+		// Time: now + 1
+		// The message should no longer be sendable via the faster transport,
+		// as the ETA is now equal
+		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE,
+				MAX_LATENCY - 1);
+		assertTrue(ids.isEmpty());
+
+		db.commitTransaction(txn);
+		db.close();
+	}
+
+
 	private Database<Connection> open(boolean resume) throws Exception {
 		return open(resume, new TestMessageFactory(), new SystemClock());
 	}
@@ -1846,7 +1949,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 	@After
 	public void tearDown() {
-		TestUtils.deleteTestDirectory(testDir);
+		deleteTestDirectory(testDir);
 	}
 
 	private static class StoppedClock implements Clock {