Add migration that drops offers table.

bramble-api/src/main/java/org/briarproject/bramble/api/Consumable.java

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.api;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import javax.annotation.Nullable;
+
+/**
+ * An item that can be consumed once.
+ */
+@NotNullByDefault
+public class Consumable<T> {
+
+	private final AtomicReference<T> reference;
+
+	public Consumable(T item) {
+		reference = new AtomicReference<>(item);
+	}
+
+	@Nullable
+	public T consume() {
+		return reference.getAndSet(null);
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -181,14 +181,6 @@ public interface DatabaseComponent extends TransactionManager {
 	Offer generateOffer(Transaction txn, ContactId c, int maxMessages,
 			int maxLatency, boolean small) throws DbException;
 
-	/**
-	 * Returns a request for the given contact, or null if there are no
-	 * messages to request.
-	 */
-	@Nullable
-	Request generateRequest(Transaction txn, ContactId c, int maxMessages)
-			throws DbException;
-
 	/**
 	 * Returns a batch of messages for the given contact, with a total length
 	 * less than or equal to the given length, for transmission over a

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessageToRequestEvent.java

@@ -1,26 +0,0 @@
-package org.briarproject.bramble.api.sync.event;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when a message is offered by a contact and needs
- * to be requested.
- */
-@Immutable
-@NotNullByDefault
-public class MessageToRequestEvent extends Event {
-
-	private final ContactId contactId;
-
-	public MessageToRequestEvent(ContactId contactId) {
-		this.contactId = contactId;
-	}
-
-	public ContactId getContactId() {
-		return contactId;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesToAckEvent.java

@@ -7,16 +7,16 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import javax.annotation.concurrent.Immutable;
 
 /**
- * An event that is broadcast when a message is received from, or offered by, a
- * contact and needs to be acknowledged.
+ * An event that is broadcast when one or more messages are received from, or
+ * offered by, a contact and need to be acknowledged.
  */
 @Immutable
 @NotNullByDefault
-public class MessageToAckEvent extends Event {
+public class MessagesToAckEvent extends Event {
 
 	private final ContactId contactId;
 
-	public MessageToAckEvent(ContactId contactId) {
+	public MessagesToAckEvent(ContactId contactId) {
 		this.contactId = contactId;
 	}
 

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesToRequestEvent.java

@@ -0,0 +1,39 @@
+package org.briarproject.bramble.api.sync.event;
+
+import org.briarproject.bramble.api.Consumable;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
+
+import java.util.Collection;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when one or more messages are offered by a
+ * contact and need to be requested.
+ */
+@Immutable
+@NotNullByDefault
+public class MessagesToRequestEvent extends Event {
+
+	private final ContactId contactId;
+	private final Consumable<Collection<MessageId>> ids;
+
+	public MessagesToRequestEvent(ContactId contactId,
+			Collection<MessageId> ids) {
+		this.contactId = contactId;
+		this.ids = new Consumable<>(ids);
+	}
+
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	@Nullable
+	public Collection<MessageId> consumeIds() {
+		return ids.consume();
+	}
+}

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

@@ -126,11 +126,6 @@ interface Database<T> {
 	void addMessageDependency(T txn, Message dependent, MessageId dependency,
 			MessageState dependentState) throws DbException;
 
-	/**
-	 * Records that a message has been offered by the given contact.
-	 */
-	void addOfferedMessage(T txn, ContactId c, MessageId m) throws DbException;
-
 	/**
 	 * Stores a pending contact.
 	 */
@@ -219,13 +214,6 @@ interface Database<T> {
 	boolean containsVisibleMessage(T txn, ContactId c, MessageId m)
 			throws DbException;
 
-	/**
-	 * Returns the number of messages offered by the given contact.
-	 * <p/>
-	 * Read-only.
-	 */
-	int countOfferedMessages(T txn, ContactId c) throws DbException;
-
 	/**
 	 * Deletes the message with the given ID. Unlike
 	 * {@link #removeMessage(Object, MessageId)}, the message ID and any other
@@ -467,15 +455,6 @@ interface Database<T> {
 	Collection<MessageId> getSmallMessagesToOffer(T txn, ContactId c,
 			int maxMessages, int maxLatency) throws DbException;
 
-	/**
-	 * Returns the IDs of some messages that are eligible to be requested from
-	 * the given contact, up to the given number of messages.
-	 * <p/>
-	 * Read-only.
-	 */
-	Collection<MessageId> getMessagesToRequest(T txn, ContactId c,
-			int maxMessages) throws DbException;
-
 	/**
 	 * Returns the IDs of some messages that are eligible to be sent to the
 	 * given contact, up to the given total length.
@@ -656,13 +635,6 @@ interface Database<T> {
 	 */
 	void removeMessage(T txn, MessageId m) throws DbException;
 
-	/**
-	 * Removes the given offered messages that were offered by the given
-	 * contact.
-	 */
-	void removeOfferedMessages(T txn, ContactId c,
-			Collection<MessageId> requested) throws DbException;
-
 	/**
 	 * Removes a pending contact (and all associated state) from the database.
 	 */

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

@@ -61,10 +61,10 @@ import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
 import org.briarproject.bramble.api.sync.event.MessageStateChangedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToAckEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToRequestEvent;
 import org.briarproject.bramble.api.sync.event.SyncVersionsUpdatedEvent;
 import org.briarproject.bramble.api.sync.validation.MessageState;
 import org.briarproject.bramble.api.transport.KeySetId;
@@ -91,7 +91,6 @@ import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.UNKNOWN;
-import static org.briarproject.bramble.db.DatabaseConstants.MAX_OFFERED_MESSAGES;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
@@ -416,12 +415,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (small)
 			ids = db.getSmallMessagesToSend(txn, c, maxLength, maxLatency);
 		else ids = db.getMessagesToSend(txn, c, maxLength, maxLatency);
+		if (ids.isEmpty()) return null;
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
 			messages.add(db.getSmallMessage(txn, m));
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
-		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
 		transaction.attach(new MessagesSentEvent(c, ids));
 		return messages;
@@ -445,21 +444,6 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return new Offer(ids);
 	}
 
-	@Nullable
-	@Override
-	public Request generateRequest(Transaction transaction, ContactId c,
-			int maxMessages) throws DbException {
-		if (transaction.isReadOnly()) throw new IllegalArgumentException();
-		T txn = unbox(transaction);
-		if (!db.containsContact(txn, c))
-			throw new NoSuchContactException();
-		Collection<MessageId> ids =
-				db.getMessagesToRequest(txn, c, maxMessages);
-		if (ids.isEmpty()) return null;
-		db.removeOfferedMessages(txn, c, ids);
-		return new Request(ids);
-	}
-
 	@Nullable
 	@Override
 	public Collection<Message> generateRequestedBatch(Transaction transaction,
@@ -470,12 +454,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		Collection<MessageId> ids =
 				db.getRequestedMessagesToSend(txn, c, maxLength, maxLatency);
+		if (ids.isEmpty()) return null;
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
 			messages.add(db.getSmallMessage(txn, m));
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
-		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
 		transaction.attach(new MessagesSentEvent(c, ids));
 		return messages;
@@ -824,7 +808,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 				db.addMessage(txn, m, UNKNOWN, false, false, c);
 				transaction.attach(new MessageAddedEvent(m, c));
 			}
-			transaction.attach(new MessageToAckEvent(c));
+			transaction.attach(new MessagesToAckEvent(c));
 		}
 	}
 
@@ -835,21 +819,20 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		boolean ack = false, request = false;
-		int count = db.countOfferedMessages(txn, c);
+		boolean ack = false;
+		List<MessageId> request = new ArrayList<>(o.getMessageIds().size());
 		for (MessageId m : o.getMessageIds()) {
 			if (db.containsVisibleMessage(txn, c, m)) {
 				db.raiseSeenFlag(txn, c, m);
 				db.raiseAckFlag(txn, c, m);
 				ack = true;
-			} else if (count < MAX_OFFERED_MESSAGES) {
-				db.addOfferedMessage(txn, c, m);
-				request = true;
-				count++;
+			} else {
+				request.add(m);
 			}
 		}
-		if (ack) transaction.attach(new MessageToAckEvent(c));
-		if (request) transaction.attach(new MessageToRequestEvent(c));
+		if (ack) transaction.attach(new MessagesToAckEvent(c));
+		if (!request.isEmpty())
+			transaction.attach(new MessagesToRequestEvent(c, request));
 	}
 
 	@Override

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

@@ -6,13 +6,6 @@ import static java.util.concurrent.TimeUnit.DAYS;
 
 interface DatabaseConstants {
 
-	/**
-	 * The maximum number of offered messages from each contact that will be
-	 * stored. If offers arrive more quickly than requests can be sent and this
-	 * limit is reached, additional offers will not be stored.
-	 */
-	int MAX_OFFERED_MESSAGES = 1000;
-
 	/**
 	 * The namespace of the {@link Settings} where the database schema version
 	 * is stored.

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

@@ -99,7 +99,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 48;
+	static final int CODE_SCHEMA_VERSION = 49;
 
 	// Time period offsets for incoming transport keys
 	private static final int OFFSET_PREV = -1;
@@ -220,15 +220,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES messages (messageId)"
 					+ " ON DELETE CASCADE)";
 
-	private static final String CREATE_OFFERS =
-			"CREATE TABLE offers"
-					+ " (messageId _HASH NOT NULL," // Not a foreign key
-					+ " contactId INT NOT NULL,"
-					+ " PRIMARY KEY (messageId, contactId),"
-					+ " FOREIGN KEY (contactId)"
-					+ " REFERENCES contacts (contactId)"
-					+ " ON DELETE CASCADE)";
-
 	private static final String CREATE_BLOCKS =
 			"CREATE TABLE blocks"
 					+ " (messageId _HASH NOT NULL,"
@@ -476,7 +467,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 				new Migration44_45(),
 				new Migration45_46(),
 				new Migration46_47(dbTypes),
-				new Migration47_48(dbTypes)
+				new Migration47_48(dbTypes),
+				new Migration48_49()
 		);
 	}
 
@@ -521,7 +513,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGES));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_METADATA));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_DEPENDENCIES));
-			s.executeUpdate(dbTypes.replaceTypes(CREATE_OFFERS));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_BLOCKS));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_STATUSES));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_TRANSPORTS));
@@ -753,9 +744,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 				boolean messageShared = rs.getBoolean(4);
 				int length = rs.getInt(5);
 				boolean deleted = rs.getBoolean(6);
-				boolean seen = removeOfferedMessage(txn, c, id);
 				addStatus(txn, id, c, g, timestamp, length, state, groupShared,
-						messageShared, deleted, seen);
+						messageShared, deleted, false);
 			}
 			rs.close();
 			ps.close();
@@ -830,8 +820,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					getGroupVisibility(txn, m.getGroupId());
 			for (Entry<ContactId, Boolean> e : visibility.entrySet()) {
 				ContactId c = e.getKey();
-				boolean offered = removeOfferedMessage(txn, c, m.getId());
-				boolean seen = offered || c.equals(sender);
+				boolean seen = c.equals(sender);
 				addStatus(txn, m.getId(), c, m.getGroupId(), m.getTimestamp(),
 						m.getRawLength(), state, e.getValue(), shared, false,
 						seen);
@@ -853,37 +842,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public void addOfferedMessage(Connection txn, ContactId c, MessageId m)
-			throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT NULL FROM offers"
-					+ " WHERE messageId = ? AND contactId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setInt(2, c.getInt());
-			rs = ps.executeQuery();
-			boolean found = rs.next();
-			if (rs.next()) throw new DbStateException();
-			rs.close();
-			ps.close();
-			if (found) return;
-			sql = "INSERT INTO offers (messageId, contactId) VALUES (?, ?)";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setInt(2, c.getInt());
-			int affected = ps.executeUpdate();
-			if (affected != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	private void addStatus(Connection txn, MessageId m, ContactId c, GroupId g,
 			long timestamp, int length, MessageState state, boolean groupShared,
 			boolean messageShared, boolean deleted, boolean seen)
@@ -1285,30 +1243,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public int countOfferedMessages(Connection txn, ContactId c)
-			throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT COUNT (messageId) FROM offers "
-					+ " WHERE contactId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			rs = ps.executeQuery();
-			if (!rs.next()) throw new DbException();
-			int count = rs.getInt(1);
-			if (rs.next()) throw new DbException();
-			rs.close();
-			ps.close();
-			return count;
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public void deleteMessage(Connection txn, MessageId m) throws DbException {
 		PreparedStatement ps = null;
@@ -2177,31 +2111,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public Collection<MessageId> getMessagesToRequest(Connection txn,
-			ContactId c, int maxMessages) throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT messageId FROM offers"
-					+ " WHERE contactId = ?"
-					+ " LIMIT ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			ps.setInt(2, maxMessages);
-			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
-			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
-			rs.close();
-			ps.close();
-			return ids;
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public Collection<MessageId> getMessagesToSend(Connection txn, ContactId c,
 			int maxLength, int maxLatency) throws DbException {
@@ -3005,50 +2914,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private boolean removeOfferedMessage(Connection txn, ContactId c,
-			MessageId m) throws DbException {
-		PreparedStatement ps = null;
-		try {
-			String sql = "DELETE FROM offers"
-					+ " WHERE contactId = ? AND messageId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			ps.setBytes(2, m.getBytes());
-			int affected = ps.executeUpdate();
-			if (affected < 0 || affected > 1) throw new DbStateException();
-			ps.close();
-			return affected == 1;
-		} catch (SQLException e) {
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
-	@Override
-	public void removeOfferedMessages(Connection txn, ContactId c,
-			Collection<MessageId> requested) throws DbException {
-		PreparedStatement ps = null;
-		try {
-			String sql = "DELETE FROM offers"
-					+ " WHERE contactId = ? AND messageId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			for (MessageId m : requested) {
-				ps.setBytes(2, m.getBytes());
-				ps.addBatch();
-			}
-			int[] batchAffected = ps.executeBatch();
-			if (batchAffected.length != requested.size())
-				throw new DbStateException();
-			for (int rows : batchAffected)
-				if (rows != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public void removePendingContact(Connection txn, PendingContactId p)
 			throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/db/Migration48_49.java

@@ -0,0 +1,40 @@
+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 static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
+
+class Migration48_49 implements Migration<Connection> {
+
+	private static final Logger LOG = getLogger(Migration48_49.class.getName());
+
+	@Override
+	public int getStartVersion() {
+		return 48;
+	}
+
+	@Override
+	public int getEndVersion() {
+		return 49;
+	}
+
+	@Override
+	public void migrate(Connection txn) throws DbException {
+		Statement s = null;
+		try {
+			s = txn.createStatement();
+			s.execute("DROP TABLE offers");
+			s.close();
+		} catch (SQLException e) {
+			tryToClose(s, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
 import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.Request;
@@ -25,8 +26,8 @@ import org.briarproject.bramble.api.sync.event.CloseSyncConnectionsEvent;
 import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToAckEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToRequestEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.transport.StreamWriter;
 
@@ -87,8 +88,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private final AtomicBoolean generateAckQueued = new AtomicBoolean(false);
 	private final AtomicBoolean generateBatchQueued = new AtomicBoolean(false);
 	private final AtomicBoolean generateOfferQueued = new AtomicBoolean(false);
-	private final AtomicBoolean generateRequestQueued =
-			new AtomicBoolean(false);
 	private final AtomicLong nextSendTime = new AtomicLong(Long.MAX_VALUE);
 
 	private volatile boolean interrupted = false;
@@ -125,7 +124,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			generateAck();
 			generateBatch();
 			generateOffer();
-			generateRequest();
 			long now = clock.currentTimeMillis();
 			long nextKeepalive = now + maxIdleTime;
 			boolean dataToFlush = true;
@@ -197,11 +195,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			dbExecutor.execute(new GenerateOffer());
 	}
 
-	private void generateRequest() {
-		if (generateRequestQueued.compareAndSet(false, true))
-			dbExecutor.execute(new GenerateRequest());
-	}
-
 	private void setNextSendTime(long time) {
 		long old = nextSendTime.getAndSet(time);
 		if (time < old) writerTasks.add(NEXT_SEND_TIME_DECREASED);
@@ -227,12 +220,16 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		} else if (e instanceof MessageRequestedEvent) {
 			if (((MessageRequestedEvent) e).getContactId().equals(contactId))
 				generateBatch();
-		} else if (e instanceof MessageToAckEvent) {
-			if (((MessageToAckEvent) e).getContactId().equals(contactId))
+		} else if (e instanceof MessagesToAckEvent) {
+			if (((MessagesToAckEvent) e).getContactId().equals(contactId))
 				generateAck();
-		} else if (e instanceof MessageToRequestEvent) {
-			if (((MessageToRequestEvent) e).getContactId().equals(contactId))
-				generateRequest();
+		} else if (e instanceof MessagesToRequestEvent) {
+			MessagesToRequestEvent m = (MessagesToRequestEvent) e;
+			if (m.getContactId().equals(contactId)) {
+				Collection<MessageId> ids = m.consumeIds();
+				if (ids != null)
+					writerTasks.add(new WriteRequest(new Request(ids)));
+			}
 		} else if (e instanceof LifecycleEvent) {
 			LifecycleEvent l = (LifecycleEvent) e;
 			if (l.getLifecycleState() == STOPPING) interrupt();
@@ -372,27 +369,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		}
 	}
 
-	private class GenerateRequest implements Runnable {
-
-		@DatabaseExecutor
-		@Override
-		public void run() {
-			if (interrupted) return;
-			if (!generateRequestQueued.getAndSet(false))
-				throw new AssertionError();
-			try {
-				Request r = db.transactionWithNullableResult(false, txn ->
-						db.generateRequest(txn, contactId, MAX_MESSAGE_IDS));
-				if (LOG.isLoggable(INFO))
-					LOG.info("Generated request: " + (r != null));
-				if (r != null) writerTasks.add(new WriteRequest(r));
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				interrupt();
-			}
-		}
-	}
-
 	private class WriteRequest implements ThrowingRunnable<IOException> {
 
 		private final Request request;
@@ -407,7 +383,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			if (interrupted) return;
 			recordWriter.writeRequest(request);
 			LOG.info("Sent request");
-			generateRequest();
 		}
 	}
 }

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

@@ -44,10 +44,10 @@ import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
 import org.briarproject.bramble.api.sync.event.MessageStateChangedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToAckEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToRequestEvent;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
@@ -76,7 +76,6 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.UNKNOWN;
 import static org.briarproject.bramble.api.transport.TransportConstants.REORDERING_WINDOW_SIZE;
-import static org.briarproject.bramble.db.DatabaseConstants.MAX_OFFERED_MESSAGES;
 import static org.briarproject.bramble.test.TestUtils.getAgreementPrivateKey;
 import static org.briarproject.bramble.test.TestUtils.getAgreementPublicKey;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
@@ -295,11 +294,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the contact is in the DB (which it's not)
-			exactly(18).of(database).startTransaction();
+			exactly(17).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(18).of(database).containsContact(txn, contactId);
+			exactly(17).of(database).containsContact(txn, contactId);
 			will(returnValue(false));
-			exactly(18).of(database).abortTransaction(txn);
+			exactly(17).of(database).abortTransaction(txn);
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -337,14 +336,6 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// Expected
 		}
 
-		try {
-			db.transaction(false, transaction ->
-					db.generateRequest(transaction, contactId, 123));
-			fail();
-		} catch (NoSuchContactException expected) {
-			// Expected
-		}
-
 		try {
 			db.transaction(false, transaction ->
 					db.getContact(transaction, contactId));
@@ -917,30 +908,6 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		});
 	}
 
-	@Test
-	public void testGenerateRequest() throws Exception {
-		MessageId messageId1 = new MessageId(getRandomId());
-		Collection<MessageId> ids = asList(messageId, messageId1);
-		context.checking(new Expectations() {{
-			oneOf(database).startTransaction();
-			will(returnValue(txn));
-			oneOf(database).containsContact(txn, contactId);
-			will(returnValue(true));
-			oneOf(database).getMessagesToRequest(txn, contactId, 123);
-			will(returnValue(ids));
-			oneOf(database).removeOfferedMessages(txn, contactId, ids);
-			oneOf(database).commitTransaction(txn);
-		}});
-		DatabaseComponent db = createDatabaseComponent(database, eventBus,
-				eventExecutor, shutdownManager);
-
-		db.transaction(false, transaction -> {
-			Request r = db.generateRequest(transaction, contactId, 123);
-			assertNotNull(r);
-			assertEquals(ids, r.getMessageIds());
-		});
-	}
-
 	@Test
 	public void testGenerateRequestedBatch() throws Exception {
 		Collection<MessageId> ids = asList(messageId, messageId1);
@@ -1020,10 +987,10 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).raiseAckFlag(txn, contactId, messageId);
 			oneOf(database).commitTransaction(txn);
 			// First time: the message was received and added
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
 			oneOf(eventBus).broadcast(with(any(MessageAddedEvent.class)));
 			// Second time: the message needs to be acked
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -1051,7 +1018,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).raiseAckFlag(txn, contactId, messageId);
 			oneOf(database).commitTransaction(txn);
 			// The message was received but not added
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -1082,19 +1049,15 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 	public void testReceiveOffer() throws Exception {
 		MessageId messageId1 = new MessageId(getRandomId());
 		MessageId messageId2 = new MessageId(getRandomId());
-		MessageId messageId3 = new MessageId(getRandomId());
+
 		context.checking(new Expectations() {{
 			oneOf(database).startTransaction();
 			will(returnValue(txn));
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
-			// There's room for two more offered messages
-			oneOf(database).countOfferedMessages(txn, contactId);
-			will(returnValue(MAX_OFFERED_MESSAGES - 2));
 			// The first message isn't visible - request it
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId);
 			will(returnValue(false));
-			oneOf(database).addOfferedMessage(txn, contactId, messageId);
 			// The second message is visible - ack it
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId1);
 			will(returnValue(true));
@@ -1103,19 +1066,14 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// The third message isn't visible - request it
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId2);
 			will(returnValue(false));
-			oneOf(database).addOfferedMessage(txn, contactId, messageId2);
-			// The fourth message isn't visible, but there's no room to store it
-			oneOf(database).containsVisibleMessage(txn, contactId, messageId3);
-			will(returnValue(false));
 			oneOf(database).commitTransaction(txn);
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
-			oneOf(eventBus).broadcast(with(any(MessageToRequestEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToRequestEvent.class)));
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
 
-		Offer o = new Offer(asList(messageId, messageId1,
-				messageId2, messageId3));
+		Offer o = new Offer(asList(messageId, messageId1, messageId2));
 		db.transaction(false, transaction ->
 				db.receiveOffer(transaction, contactId, o));
 	}

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

@@ -41,7 +41,6 @@ import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getIdentity;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
-import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
 import static org.briarproject.bramble.test.UTest.Result.INCONCLUSIVE;
 import static org.briarproject.bramble.test.UTest.Z_CRITICAL_0_1;
@@ -81,7 +80,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 	private static final int METADATA_KEYS_PER_MESSAGE = 5;
 	private static final int METADATA_KEY_LENGTH = 10;
 	private static final int METADATA_VALUE_LENGTH = 100;
-	private static final int OFFERED_MESSAGES_PER_CONTACT = 100;
 
 	/**
 	 * How many benchmark iterations to run in each block.
@@ -192,16 +190,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		});
 	}
 
-	@Test
-	public void testCountOfferedMessages() throws Exception {
-		String name = "countOfferedMessages(T, ContactId)";
-		benchmark(name, db -> {
-			Connection txn = db.startTransaction();
-			db.countOfferedMessages(txn, pickRandom(contacts).getId());
-			db.commitTransaction(txn);
-		});
-	}
-
 	@Test
 	public void testGetContact() throws Exception {
 		String name = "getContact(T, ContactId)";
@@ -454,17 +442,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		});
 	}
 
-	@Test
-	public void testGetMessagesToRequest() throws Exception {
-		String name = "getMessagesToRequest(T, ContactId, int)";
-		benchmark(name, db -> {
-			Connection txn = db.startTransaction();
-			db.getMessagesToRequest(txn, pickRandom(contacts).getId(),
-					MAX_MESSAGE_IDS);
-			db.commitTransaction(txn);
-		});
-	}
-
 	@Test
 	public void testGetMessagesToSend() throws Exception {
 		String name = "getMessagesToSend(T, ContactId, int)";
@@ -583,9 +560,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 					groupMessages.get(g.getId()).add(m.getId());
 				}
 			}
-			for (int j = 0; j < OFFERED_MESSAGES_PER_CONTACT; j++) {
-				db.addOfferedMessage(txn, c, new MessageId(getRandomId()));
-			}
 		}
 		for (int i = 0; i < LOCAL_GROUPS; i++) {
 			Group g = getGroup(clientIds.get(i % CLIENTS), 123);

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

@@ -41,7 +41,6 @@ import org.junit.Test;
 
 import java.io.File;
 import java.sql.Connection;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -1187,35 +1186,6 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
-	@Test
-	public void testOfferedMessages() throws Exception {
-		Database<Connection> db = open(false);
-		Connection txn = db.startTransaction();
-
-		// Add a contact - initially there should be no offered messages
-		db.addIdentity(txn, identity);
-		assertEquals(contactId,
-				db.addContact(txn, author, localAuthor.getId(), null, true));
-		assertEquals(0, db.countOfferedMessages(txn, contactId));
-
-		// Add some offered messages and count them
-		List<MessageId> ids = new ArrayList<>();
-		for (int i = 0; i < 10; i++) {
-			MessageId m = new MessageId(getRandomId());
-			db.addOfferedMessage(txn, contactId, m);
-			ids.add(m);
-		}
-		assertEquals(10, db.countOfferedMessages(txn, contactId));
-
-		// Remove some of the offered messages and count again
-		List<MessageId> half = ids.subList(0, 5);
-		db.removeOfferedMessages(txn, contactId, half);
-		assertEquals(5, db.countOfferedMessages(txn, contactId));
-
-		db.commitTransaction(txn);
-		db.close();
-	}
-
 	@Test
 	public void testGroupMetadata() throws Exception {
 		Database<Connection> db = open(false);