Merge branch '2291-mailbox-upload-worker' into 'master'

Mailbox upload worker

Closes #2291

See merge request briar/briar!1673

bramble-api/src/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -40,7 +40,7 @@ public class IoUtils {
 		}
 	}
 
-	private static void delete(File f) {
+	public static void delete(File f) {
 		if (!f.delete() && LOG.isLoggable(WARNING))
 			LOG.warning("Could not delete " + f.getAbsolutePath());
 	}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxDownloadWorker.java

@@ -146,10 +146,12 @@ class ContactMailboxDownloadWorker implements MailboxWorker,
 			if (state == State.DOWNLOAD_CYCLE_1) {
 				LOG.info("First download cycle finished");
 				state = State.WAITING_FOR_TOR;
+				apiCall = null;
 				addObserver = true;
 			} else if (state == State.DOWNLOAD_CYCLE_2) {
 				LOG.info("Second download cycle finished");
 				state = State.FINISHED;
+				apiCall = null;
 			}
 		}
 		if (addObserver) {

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxFileManager.java

@@ -1,6 +1,8 @@
 package org.briarproject.bramble.mailbox;
 
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 import java.io.File;
 import java.io.IOException;
@@ -16,6 +18,14 @@ interface MailboxFileManager {
 	 */
 	File createTempFileForDownload() throws IOException;
 
+	/**
+	 * Creates a file to be uploaded to the given contact and writes any
+	 * waiting data to the file. The IDs of any messages sent or acked will
+	 * be added to the given {@link OutgoingSessionRecord}.
+	 */
+	File createAndWriteTempFileForUpload(ContactId contactId,
+			OutgoingSessionRecord sessionRecord) throws IOException;
+
 	/**
 	 * Handles a file that has been downloaded. The file should be created
 	 * with {@link #createTempFileForDownload()}.

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxFileManagerImpl.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.mailbox;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -10,13 +11,18 @@ import org.briarproject.bramble.api.mailbox.MailboxDirectory;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
+import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
@@ -30,6 +36,7 @@ import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleS
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.api.plugin.file.FileConstants.PROP_PATH;
+import static org.briarproject.bramble.util.IoUtils.delete;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @ThreadSafe
@@ -41,6 +48,7 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	// Package access for testing
 	static final String DOWNLOAD_DIR_NAME = "downloads";
+	static final String UPLOAD_DIR_NAME = "uploads";
 
 	private final Executor ioExecutor;
 	private final PluginManager pluginManager;
@@ -67,14 +75,44 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	@Override
 	public File createTempFileForDownload() throws IOException {
+		return createTempFile(DOWNLOAD_DIR_NAME);
+	}
+
+	@Override
+	public File createAndWriteTempFileForUpload(ContactId contactId,
+			OutgoingSessionRecord sessionRecord) throws IOException {
+		File f = createTempFile(UPLOAD_DIR_NAME);
+		// We shouldn't reach this point until the plugin has been started
+		SimplexPlugin plugin =
+				(SimplexPlugin) requireNonNull(pluginManager.getPlugin(ID));
+		TransportProperties p = new TransportProperties();
+		p.put(PROP_PATH, f.getAbsolutePath());
+		TransportConnectionWriter writer = plugin.createWriter(p);
+		if (writer == null) {
+			delete(f);
+			throw new IOException();
+		}
+		MailboxFileWriter decorated = new MailboxFileWriter(writer);
+		LOG.info("Writing file for upload");
+		connectionManager.manageOutgoingConnection(contactId, ID, decorated,
+				sessionRecord);
+		if (decorated.awaitDisposal()) {
+			// An exception was thrown during the session - delete the file
+			delete(f);
+			throw new IOException();
+		}
+		return f;
+	}
+
+	private File createTempFile(String dirName) throws IOException {
 		// Wait for orphaned files to be handled before creating new files
 		try {
 			orphanLatch.await();
 		} catch (InterruptedException e) {
 			throw new IOException(e);
 		}
-		File downloadDir = createDirectoryIfNeeded(DOWNLOAD_DIR_NAME);
-		return File.createTempFile("mailbox", ".tmp", downloadDir);
+		File dir = createDirectoryIfNeeded(dirName);
+		return File.createTempFile("mailbox", ".tmp", dir);
 	}
 
 	private File createDirectoryIfNeeded(String name) throws IOException {
@@ -116,6 +154,8 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
+		// Wait for the transport to become active before handling orphaned
+		// files so that we can get the plugin from the plugin manager
 		if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			if (t.getTransportId().equals(ID)) {
@@ -127,17 +167,25 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	/**
 	 * This method is called at startup, as soon as the plugin is started, to
-	 * handle any files that were left in the download directory at the last
-	 * shutdown.
+	 * delete any files that were left in the upload directory at the last
+	 * shutdown and handle any files that were left in the download directory.
 	 */
 	@IoExecutor
 	private void handleOrphanedFiles() {
 		try {
+			File uploadDir = createDirectoryIfNeeded(UPLOAD_DIR_NAME);
+			File[] orphanedUploads = uploadDir.listFiles();
+			if (orphanedUploads != null) {
+				for (File f : orphanedUploads) delete(f);
+			}
 			File downloadDir = createDirectoryIfNeeded(DOWNLOAD_DIR_NAME);
-			File[] orphans = downloadDir.listFiles();
-			// Now that we've got the list of orphans, new files can be created
+			File[] orphanedDownloads = downloadDir.listFiles();
+			// Now that we've got the list of orphaned downloads, new files
+			// can be created in the download directory
 			orphanLatch.countDown();
-			if (orphans != null) for (File f : orphans) handleDownloadedFile(f);
+			if (orphanedDownloads != null) {
+				for (File f : orphanedDownloads) handleDownloadedFile(f);
+			}
 		} catch (IOException e) {
 			logException(LOG, WARNING, e);
 		}
@@ -165,9 +213,58 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 			delegate.dispose(exception, recognised);
 			if (isHandlingComplete(exception, recognised)) {
 				LOG.info("Deleting downloaded file");
-				if (!file.delete()) {
-					LOG.warning("Failed to delete downloaded file");
-				}
+				delete(file);
+			}
+		}
+	}
+
+	private static class MailboxFileWriter
+			implements TransportConnectionWriter {
+
+		private final TransportConnectionWriter delegate;
+		private final BlockingQueue<Boolean> disposalResult =
+				new ArrayBlockingQueue<>(1);
+
+		private MailboxFileWriter(TransportConnectionWriter delegate) {
+			this.delegate = delegate;
+		}
+
+		@Override
+		public long getMaxLatency() {
+			return delegate.getMaxLatency();
+		}
+
+		@Override
+		public int getMaxIdleTime() {
+			return delegate.getMaxIdleTime();
+		}
+
+		@Override
+		public boolean isLossyAndCheap() {
+			return delegate.isLossyAndCheap();
+		}
+
+		@Override
+		public OutputStream getOutputStream() throws IOException {
+			return delegate.getOutputStream();
+		}
+
+		@Override
+		public void dispose(boolean exception) throws IOException {
+			delegate.dispose(exception);
+			disposalResult.add(exception);
+		}
+
+		/**
+		 * Waits for the delegate to be disposed and returns true if an
+		 * exception occurred.
+		 */
+		private boolean awaitDisposal() {
+			try {
+				return disposalResult.take();
+			} catch (InterruptedException e) {
+				LOG.info("Interrupted while waiting for disposal");
+				return true;
 			}
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxUploadWorker.java

@@ -0,0 +1,394 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventExecutor;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
+import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
+import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
+import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
+import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_LATENCY;
+import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
+import static org.briarproject.bramble.util.IoUtils.delete;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@ThreadSafe
+@NotNullByDefault
+class MailboxUploadWorker implements MailboxWorker, ConnectivityObserver,
+		EventListener {
+
+	/**
+	 * When the worker is started it checks for data to send. If data is ready
+	 * to send, the worker waits for a connectivity check, then writes and
+	 * uploads a file and checks again for data to send.
+	 * <p>
+	 * If data is due to be sent at some time in the future, the worker
+	 * schedules a wakeup for that time and also listens for events indicating
+	 * that new data may be ready to send.
+	 * <p>
+	 * If there's no data to send, the worker listens for events indicating
+	 * that new data may be ready to send.
+	 */
+	private enum State {
+		CREATED,
+		CHECKING_FOR_DATA,
+		WAITING_FOR_DATA,
+		CONNECTIVITY_CHECK,
+		WRITING_UPLOADING,
+		DESTROYED
+	}
+
+	private static final Logger LOG =
+			getLogger(MailboxUploadWorker.class.getName());
+
+	/**
+	 * When we're waiting for data to send and an event indicates that new data
+	 * may have become available, wait this long before checking the DB. This
+	 * should help to avoid creating lots of small files when several acks or
+	 * messages become available to send in a short period (eg when reading a
+	 * file downloaded from a mailbox).
+	 * <p>
+	 * Package access for testing.
+	 */
+	static final long CHECK_DELAY_MS = 5_000;
+
+	/**
+	 * How long to wait before retrying when an exception occurs while writing
+	 * a file.
+	 * <p>
+	 * Package access for testing.
+	 */
+	static final long RETRY_DELAY_MS = MINUTES.toMillis(1);
+
+	private final Executor ioExecutor;
+	private final DatabaseComponent db;
+	private final Clock clock;
+	private final TaskScheduler taskScheduler;
+	private final EventBus eventBus;
+	private final ConnectivityChecker connectivityChecker;
+	private final MailboxApiCaller mailboxApiCaller;
+	private final MailboxApi mailboxApi;
+	private final MailboxFileManager mailboxFileManager;
+	private final MailboxProperties mailboxProperties;
+	private final MailboxFolderId folderId;
+	private final ContactId contactId;
+
+	private final Object lock = new Object();
+
+	@GuardedBy("lock")
+	private State state = State.CREATED;
+
+	@GuardedBy("lock")
+	@Nullable
+	private Cancellable wakeupTask = null, checkTask = null, apiCall = null;
+
+	@GuardedBy("lock")
+	@Nullable
+	private File file = null;
+
+	MailboxUploadWorker(@IoExecutor Executor ioExecutor,
+			DatabaseComponent db,
+			Clock clock,
+			TaskScheduler taskScheduler,
+			EventBus eventBus,
+			ConnectivityChecker connectivityChecker,
+			MailboxApiCaller mailboxApiCaller,
+			MailboxApi mailboxApi,
+			MailboxFileManager mailboxFileManager,
+			MailboxProperties mailboxProperties,
+			MailboxFolderId folderId,
+			ContactId contactId) {
+		this.ioExecutor = ioExecutor;
+		this.db = db;
+		this.clock = clock;
+		this.taskScheduler = taskScheduler;
+		this.eventBus = eventBus;
+		this.connectivityChecker = connectivityChecker;
+		this.mailboxApiCaller = mailboxApiCaller;
+		this.mailboxApi = mailboxApi;
+		this.mailboxFileManager = mailboxFileManager;
+		this.mailboxProperties = mailboxProperties;
+		this.folderId = folderId;
+		this.contactId = contactId;
+	}
+
+	@Override
+	public void start() {
+		LOG.info("Started");
+		synchronized (lock) {
+			// Don't allow the worker to be reused
+			if (state != State.CREATED) throw new IllegalStateException();
+			state = State.CHECKING_FOR_DATA;
+		}
+		ioExecutor.execute(this::checkForDataToSend);
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		Cancellable wakeupTask, checkTask, apiCall;
+		File file;
+		synchronized (lock) {
+			state = State.DESTROYED;
+			wakeupTask = this.wakeupTask;
+			this.wakeupTask = null;
+			checkTask = this.checkTask;
+			this.checkTask = null;
+			apiCall = this.apiCall;
+			this.apiCall = null;
+			file = this.file;
+			this.file = null;
+		}
+		if (wakeupTask != null) wakeupTask.cancel();
+		if (checkTask != null) checkTask.cancel();
+		if (apiCall != null) apiCall.cancel();
+		if (file != null) delete(file);
+		connectivityChecker.removeObserver(this);
+		eventBus.removeListener(this);
+	}
+
+	@IoExecutor
+	private void checkForDataToSend() {
+		synchronized (lock) {
+			checkTask = null;
+			if (state != State.CHECKING_FOR_DATA) return;
+		}
+		LOG.info("Checking for data to send");
+		try {
+			db.transaction(true, txn -> {
+				long nextSendTime;
+				if (db.containsAcksToSend(txn, contactId)) {
+					nextSendTime = 0L;
+				} else {
+					nextSendTime = db.getNextSendTime(txn, contactId,
+							MAX_LATENCY);
+				}
+				// Handle the result on the event executor to avoid races with
+				// incoming events
+				txn.attach(() -> handleNextSendTime(nextSendTime));
+			});
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	@EventExecutor
+	private void handleNextSendTime(long nextSendTime) {
+		if (nextSendTime == Long.MAX_VALUE) {
+			// Nothing is sendable now or due to be sent in the future. Wait
+			// for an event indicating that new data may be ready to send
+			waitForDataToSend();
+		} else {
+			// Work out the delay until data's ready to send (may be negative)
+			long delay = nextSendTime - clock.currentTimeMillis();
+			if (delay > 0) {
+				// Schedule a wakeup when data will be ready to send. If an
+				// event is received in the meantime indicating that new data
+				// may be ready to send, we'll cancel the wakeup
+				scheduleWakeup(delay);
+			} else {
+				// Data is ready to send now
+				checkConnectivity();
+			}
+		}
+	}
+
+	@EventExecutor
+	private void waitForDataToSend() {
+		synchronized (lock) {
+			if (state != State.CHECKING_FOR_DATA) return;
+			state = State.WAITING_FOR_DATA;
+			LOG.info("Waiting for data to send");
+		}
+	}
+
+	@EventExecutor
+	private void scheduleWakeup(long delay) {
+		synchronized (lock) {
+			if (state != State.CHECKING_FOR_DATA) return;
+			state = State.WAITING_FOR_DATA;
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Scheduling wakeup in " + delay + " ms");
+			}
+			wakeupTask = taskScheduler.schedule(this::wakeUp, ioExecutor,
+					delay, MILLISECONDS);
+		}
+	}
+
+	@IoExecutor
+	private void wakeUp() {
+		LOG.info("Woke up");
+		synchronized (lock) {
+			wakeupTask = null;
+			if (state != State.WAITING_FOR_DATA) return;
+			state = State.CHECKING_FOR_DATA;
+		}
+		checkForDataToSend();
+	}
+
+	@EventExecutor
+	private void checkConnectivity() {
+		synchronized (lock) {
+			if (state != State.CHECKING_FOR_DATA) return;
+			state = State.CONNECTIVITY_CHECK;
+		}
+		LOG.info("Checking connectivity");
+		// Avoid leaking observer in case destroy() is called concurrently
+		// before observer is added
+		connectivityChecker.checkConnectivity(mailboxProperties, this);
+		boolean destroyed;
+		synchronized (lock) {
+			destroyed = state == State.DESTROYED;
+		}
+		if (destroyed) connectivityChecker.removeObserver(this);
+	}
+
+	@Override
+	public void onConnectivityCheckSucceeded() {
+		LOG.info("Connectivity check succeeded");
+		synchronized (lock) {
+			if (state != State.CONNECTIVITY_CHECK) return;
+			state = State.WRITING_UPLOADING;
+		}
+		ioExecutor.execute(this::writeAndUploadFile);
+	}
+
+	@IoExecutor
+	private void writeAndUploadFile() {
+		synchronized (lock) {
+			if (state != State.WRITING_UPLOADING) return;
+		}
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+		File file;
+		try {
+			file = mailboxFileManager.createAndWriteTempFileForUpload(
+					contactId, sessionRecord);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			// Try again after a delay
+			synchronized (lock) {
+				if (state != State.WRITING_UPLOADING) return;
+				state = State.CHECKING_FOR_DATA;
+				checkTask = taskScheduler.schedule(this::checkForDataToSend,
+						ioExecutor, RETRY_DELAY_MS, MILLISECONDS);
+			}
+			return;
+		}
+		boolean deleteFile = false;
+		synchronized (lock) {
+			if (state == State.WRITING_UPLOADING) {
+				this.file = file;
+				apiCall = mailboxApiCaller.retryWithBackoff(
+						new SimpleApiCall(() -> apiCallUploadFile(file,
+								sessionRecord)));
+			} else {
+				deleteFile = true;
+			}
+		}
+		if (deleteFile) delete(file);
+	}
+
+	@IoExecutor
+	private void apiCallUploadFile(File file,
+			OutgoingSessionRecord sessionRecord)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state != State.WRITING_UPLOADING) return;
+		}
+		LOG.info("Uploading file");
+		mailboxApi.addFile(mailboxProperties, folderId, file);
+		markMessagesSentOrAcked(sessionRecord);
+		synchronized (lock) {
+			if (state != State.WRITING_UPLOADING) return;
+			state = State.CHECKING_FOR_DATA;
+			apiCall = null;
+			this.file = null;
+		}
+		delete(file);
+		checkForDataToSend();
+	}
+
+	private void markMessagesSentOrAcked(OutgoingSessionRecord sessionRecord) {
+		Collection<MessageId> acked = sessionRecord.getAckedIds();
+		Collection<MessageId> sent = sessionRecord.getSentIds();
+		try {
+			db.transaction(false, txn -> {
+				if (!acked.isEmpty()) {
+					db.setAckSent(txn, contactId, acked);
+				}
+				if (!sent.isEmpty()) {
+					db.setMessagesSent(txn, contactId, sent, MAX_LATENCY);
+				}
+			});
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof MessageToAckEvent) {
+			MessageToAckEvent m = (MessageToAckEvent) e;
+			if (m.getContactId().equals(contactId)) {
+				LOG.info("Message to ack");
+				onDataToSend();
+			}
+		} else if (e instanceof MessageSharedEvent) {
+			LOG.info("Message shared");
+			onDataToSend();
+		} else if (e instanceof GroupVisibilityUpdatedEvent) {
+			GroupVisibilityUpdatedEvent g = (GroupVisibilityUpdatedEvent) e;
+			if (g.getVisibility() == SHARED &&
+					g.getAffectedContacts().contains(contactId)) {
+				LOG.info("Group shared");
+				onDataToSend();
+			}
+		}
+	}
+
+	@EventExecutor
+	private void onDataToSend() {
+		Cancellable wakeupTask;
+		synchronized (lock) {
+			if (state != State.WAITING_FOR_DATA) return;
+			state = State.CHECKING_FOR_DATA;
+			wakeupTask = this.wakeupTask;
+			this.wakeupTask = null;
+			// Delay the check to avoid creating lots of small files
+			checkTask = taskScheduler.schedule(this::checkForDataToSend,
+					ioExecutor, CHECK_DELAY_MS, MILLISECONDS);
+		}
+		// If we had scheduled a wakeup when data was due to be sent, cancel it
+		if (wakeupTask != null) wakeupTask.cancel();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/mailbox/ContactMailboxDownloadWorkerTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
+import org.briarproject.bramble.api.Cancellable;
 import org.briarproject.bramble.api.mailbox.MailboxFileId;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
@@ -7,6 +8,7 @@ import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.CaptureArgumentAction;
 import org.jmock.Expectations;
+import org.jmock.lib.action.DoAllAction;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -36,6 +38,7 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 	private final MailboxApi mailboxApi = context.mock(MailboxApi.class);
 	private final MailboxFileManager mailboxFileManager =
 			context.mock(MailboxFileManager.class);
+	private final Cancellable apiCall = context.mock(Cancellable.class);
 
 	private final MailboxProperties mailboxProperties =
 			getMailboxProperties(false, CLIENT_SUPPORTS);
@@ -96,30 +99,36 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 
 		// When the connectivity check succeeds, a list-inbox task should be
 		// started for the first download cycle
-		AtomicReference<ApiCall> listTask = new AtomicReference<>(null);
+		AtomicReference<ApiCall> listTask = new AtomicReference<>();
 		context.checking(new Expectations() {{
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(listTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(listTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		worker.onConnectivityCheckSucceeded();
 
 		// When the list-inbox tasks runs and finds some files to download,
 		// it should start a download task for the first file
-		AtomicReference<ApiCall> downloadTask = new AtomicReference<>(null);
+		AtomicReference<ApiCall> downloadTask = new AtomicReference<>();
 		context.checking(new Expectations() {{
 			oneOf(mailboxApi).getFiles(mailboxProperties,
 					requireNonNull(mailboxProperties.getInboxId()));
 			will(returnValue(files));
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(downloadTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(downloadTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		assertFalse(listTask.get().callApi());
 
 		// When the first download task runs it should download the file to the
 		// location provided by the file manager and start a delete task
-		AtomicReference<ApiCall> deleteTask = new AtomicReference<>(null);
+		AtomicReference<ApiCall> deleteTask = new AtomicReference<>();
 		context.checking(new Expectations() {{
 			oneOf(mailboxFileManager).createTempFileForDownload();
 			will(returnValue(tempFile));
@@ -128,7 +137,10 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 					file1.name, tempFile);
 			oneOf(mailboxFileManager).handleDownloadedFile(tempFile);
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(deleteTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(deleteTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		assertFalse(downloadTask.get().callApi());
@@ -140,7 +152,10 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 					requireNonNull(mailboxProperties.getInboxId()), file1.name);
 			will(throwException(new TolerableFailureException()));
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(downloadTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(downloadTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		assertFalse(deleteTask.get().callApi());
@@ -155,7 +170,10 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 					file2.name, tempFile);
 			oneOf(mailboxFileManager).handleDownloadedFile(tempFile);
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(deleteTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(deleteTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		assertFalse(downloadTask.get().callApi());
@@ -168,7 +186,10 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 					requireNonNull(mailboxProperties.getInboxId()), file2.name);
 			will(throwException(new TolerableFailureException()));
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(listTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(listTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		assertFalse(deleteTask.get().callApi());
@@ -188,7 +209,10 @@ public class ContactMailboxDownloadWorkerTest extends BrambleMockTestCase {
 		// be started for the second download cycle
 		context.checking(new Expectations() {{
 			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
-			will(new CaptureArgumentAction<>(listTask, ApiCall.class, 0));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(listTask, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
 		}});
 
 		worker.onTorReachable();

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxFileManagerImplTest.java

@@ -2,16 +2,20 @@ package org.briarproject.bramble.mailbox;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.connection.ConnectionManager.TagController;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
+import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.CaptureArgumentAction;
+import org.briarproject.bramble.test.ConsumeArgumentAction;
 import org.briarproject.bramble.test.RunAction;
 import org.jmock.Expectations;
 import org.jmock.lib.action.DoAllAction;
@@ -20,6 +24,7 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -28,11 +33,14 @@ import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleS
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
 import static org.briarproject.bramble.api.plugin.file.FileConstants.PROP_PATH;
 import static org.briarproject.bramble.mailbox.MailboxFileManagerImpl.DOWNLOAD_DIR_NAME;
+import static org.briarproject.bramble.mailbox.MailboxFileManagerImpl.UPLOAD_DIR_NAME;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 
@@ -47,6 +55,10 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 	private final SimplexPlugin plugin = context.mock(SimplexPlugin.class);
 	private final TransportConnectionReader transportConnectionReader =
 			context.mock(TransportConnectionReader.class);
+	private final TransportConnectionWriter transportConnectionWriter =
+			context.mock(TransportConnectionWriter.class);
+
+	private final ContactId contactId = getContactId();
 
 	private File mailboxDir;
 	private MailboxFileManagerImpl manager;
@@ -65,17 +77,25 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testHandlesOrphanedFilesAtStartup() throws Exception {
-		// Create an orphaned file, left behind at the previous shutdown
+		// Create an orphaned upload, left behind at the previous shutdown
+		File uploadDir = new File(mailboxDir, UPLOAD_DIR_NAME);
+		//noinspection ResultOfMethodCallIgnored
+		uploadDir.mkdirs();
+		File orphanedUpload = new File(uploadDir, "orphan");
+		assertTrue(orphanedUpload.createNewFile());
+
+		// Create an orphaned download, left behind at the previous shutdown
 		File downloadDir = new File(mailboxDir, DOWNLOAD_DIR_NAME);
 		//noinspection ResultOfMethodCallIgnored
 		downloadDir.mkdirs();
-		File orphan = new File(downloadDir, "orphan");
-		assertTrue(orphan.createNewFile());
+		File orphanedDownload = new File(downloadDir, "orphan");
+		assertTrue(orphanedDownload.createNewFile());
 
 		TransportProperties props = new TransportProperties();
-		props.put(PROP_PATH, orphan.getAbsolutePath());
+		props.put(PROP_PATH, orphanedDownload.getAbsolutePath());
 
-		// When the plugin becomes active the orphaned file should be handled
+		// When the plugin becomes active the orphaned upload should be deleted
+		// and the orphaned download should be handled
 		context.checking(new Expectations() {{
 			oneOf(ioExecutor).execute(with(any(Runnable.class)));
 			will(new RunAction());
@@ -90,10 +110,12 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 		}});
 
 		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		assertFalse(orphanedUpload.exists());
 	}
 
 	@Test
-	public void testDeletesFileWhenReadSucceeds() throws Exception {
+	public void testDeletesDownloadedFileWhenReadSucceeds() throws Exception {
 		expectCheckForOrphans();
 		manager.eventOccurred(new TransportActiveEvent(ID));
 
@@ -102,7 +124,7 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 				new AtomicReference<>(null);
 		AtomicReference<TagController> controller = new AtomicReference<>(null);
 
-		expectPassFileToConnectionManager(f, reader, controller);
+		expectPassDownloadedFileToConnectionManager(f, reader, controller);
 		manager.handleDownloadedFile(f);
 
 		// The read is successful, so the tag controller should allow the tag
@@ -117,29 +139,117 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testDeletesFileWhenTagIsNotRecognised() throws Exception {
-		testDeletesFile(false, RUNNING, false);
-	}
-
-	@Test
-	public void testDeletesFileWhenReadFails() throws Exception {
-		testDeletesFile(true, RUNNING, false);
-	}
-
-	@Test
-	public void testDoesNotDeleteFileWhenTagIsNotRecognisedAtShutdown()
+	public void testDeletesDownloadedFileWhenTagIsNotRecognised()
 			throws Exception {
-		testDeletesFile(false, STOPPING, true);
+		testDeletesDownloadedFile(false, RUNNING, false);
 	}
 
 	@Test
-	public void testDoesNotDeleteFileWhenReadFailsAtShutdown()
-			throws Exception {
-		testDeletesFile(true, STOPPING, true);
+	public void testDeletesDownloadedFileWhenReadFails() throws Exception {
+		testDeletesDownloadedFile(true, RUNNING, false);
 	}
 
-	private void testDeletesFile(boolean recognised, LifecycleState state,
-			boolean fileExists) throws Exception {
+	@Test
+	public void testDoesNotDeleteDownloadedFileWhenTagIsNotRecognisedAtShutdown()
+			throws Exception {
+		testDeletesDownloadedFile(false, STOPPING, true);
+	}
+
+	@Test
+	public void testDoesNotDeleteDownloadedFileWhenReadFailsAtShutdown()
+			throws Exception {
+		testDeletesDownloadedFile(true, STOPPING, true);
+	}
+
+	@Test(expected = IOException.class)
+	public void testThrowsExceptionIfPluginFailsToCreateWriter()
+			throws Exception {
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+
+		expectCheckForOrphans();
+		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		context.checking(new Expectations() {{
+			oneOf(pluginManager).getPlugin(ID);
+			will(returnValue(plugin));
+			oneOf(plugin).createWriter(with(any(TransportProperties.class)));
+			will(returnValue(null));
+		}});
+
+		manager.createAndWriteTempFileForUpload(contactId, sessionRecord);
+	}
+
+	@Test(expected = IOException.class)
+	public void testThrowsExceptionIfSessionFailsWithException()
+			throws Exception {
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+
+		expectCheckForOrphans();
+		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		context.checking(new Expectations() {{
+			oneOf(pluginManager).getPlugin(ID);
+			will(returnValue(plugin));
+			oneOf(plugin).createWriter(with(any(TransportProperties.class)));
+			will(returnValue(transportConnectionWriter));
+			oneOf(transportConnectionWriter).dispose(true);
+			oneOf(connectionManager).manageOutgoingConnection(with(contactId),
+					with(ID), with(any(TransportConnectionWriter.class)),
+					with(sessionRecord));
+			// The session fails with an exception. We need to use an action
+			// for this, as createAndWriteTempFileForUpload() waits for it to
+			// happen before returning
+			will(new ConsumeArgumentAction<>(TransportConnectionWriter.class, 2,
+					writer -> {
+						try {
+							writer.dispose(true);
+						} catch (IOException e) {
+							fail();
+						}
+					}
+			));
+		}});
+
+		manager.createAndWriteTempFileForUpload(contactId, sessionRecord);
+	}
+
+	@Test
+	public void testReturnsFileIfSessionSucceeds() throws Exception {
+		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
+
+		expectCheckForOrphans();
+		manager.eventOccurred(new TransportActiveEvent(ID));
+
+		context.checking(new Expectations() {{
+			oneOf(pluginManager).getPlugin(ID);
+			will(returnValue(plugin));
+			oneOf(plugin).createWriter(with(any(TransportProperties.class)));
+			will(returnValue(transportConnectionWriter));
+			oneOf(transportConnectionWriter).dispose(false);
+			oneOf(connectionManager).manageOutgoingConnection(with(contactId),
+					with(ID), with(any(TransportConnectionWriter.class)),
+					with(sessionRecord));
+			// The session succeeds. We need to use an action for this, as
+			// createAndWriteTempFileForUpload() waits for it to happen before
+			// returning
+			will(new ConsumeArgumentAction<>(TransportConnectionWriter.class, 2,
+					writer -> {
+						try {
+							writer.dispose(false);
+						} catch (IOException e) {
+							fail();
+						}
+					}
+			));
+		}});
+
+		File f = manager.createAndWriteTempFileForUpload(contactId,
+				sessionRecord);
+		assertTrue(f.exists());
+	}
+
+	private void testDeletesDownloadedFile(boolean recognised,
+			LifecycleState state, boolean fileExists) throws Exception {
 		expectCheckForOrphans();
 		manager.eventOccurred(new TransportActiveEvent(ID));
 
@@ -148,7 +258,7 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 				new AtomicReference<>(null);
 		AtomicReference<TagController> controller = new AtomicReference<>(null);
 
-		expectPassFileToConnectionManager(f, reader, controller);
+		expectPassDownloadedFileToConnectionManager(f, reader, controller);
 		manager.handleDownloadedFile(f);
 
 		context.checking(new Expectations() {{
@@ -169,7 +279,7 @@ public class MailboxFileManagerImplTest extends BrambleMockTestCase {
 		}});
 	}
 
-	private void expectPassFileToConnectionManager(File f,
+	private void expectPassDownloadedFileToConnectionManager(File f,
 			AtomicReference<TransportConnectionReader> reader,
 			AtomicReference<TagController> controller) {
 		TransportProperties props = new TransportProperties();

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImplTest.java

@@ -13,7 +13,6 @@ import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdate;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
-import org.briarproject.bramble.api.mailbox.event.OwnMailboxConnectionStatusEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
@@ -33,7 +32,6 @@ import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.test.TestUtils.getContact;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.test.TestUtils.hasEvent;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -138,7 +136,6 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 			i.getAndIncrement();
 		});
 		task.run();
-		hasEvent(txn, OwnMailboxConnectionStatusEvent.class);
 	}
 
 	@Test

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxSettingsManagerImplTest.java

@@ -163,7 +163,7 @@ public class MailboxSettingsManagerImplTest extends BrambleMockTestCase {
 		}});
 
 		manager.recordSuccessfulConnection(txn, now);
-		hasEvent(txn, OwnMailboxConnectionStatusEvent.class);
+		assertTrue(hasEvent(txn, OwnMailboxConnectionStatusEvent.class));
 	}
 
 	@Test

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxUploadWorkerTest.java

@@ -0,0 +1,465 @@
+package org.briarproject.bramble.mailbox;
+
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
+import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.CaptureArgumentAction;
+import org.briarproject.bramble.test.ConsumeArgumentAction;
+import org.briarproject.bramble.test.DbExpectations;
+import org.briarproject.bramble.test.RunAction;
+import org.jmock.Expectations;
+import org.jmock.lib.action.DoAllAction;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static java.util.Collections.singletonList;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_LATENCY;
+import static org.briarproject.bramble.mailbox.MailboxUploadWorker.CHECK_DELAY_MS;
+import static org.briarproject.bramble.mailbox.MailboxUploadWorker.RETRY_DELAY_MS;
+import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
+import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class MailboxUploadWorkerTest extends BrambleMockTestCase {
+
+	private final Executor ioExecutor = context.mock(Executor.class);
+	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
+	private final Clock clock = context.mock(Clock.class);
+	private final TaskScheduler taskScheduler =
+			context.mock(TaskScheduler.class);
+	private final EventBus eventBus = context.mock(EventBus.class);
+	private final ConnectivityChecker connectivityChecker =
+			context.mock(ConnectivityChecker.class);
+	private final MailboxApiCaller mailboxApiCaller =
+			context.mock(MailboxApiCaller.class);
+	private final MailboxApi mailboxApi = context.mock(MailboxApi.class);
+	private final MailboxFileManager mailboxFileManager =
+			context.mock(MailboxFileManager.class);
+	private final Cancellable apiCall =
+			context.mock(Cancellable.class, "apiCall");
+	private final Cancellable wakeupTask =
+			context.mock(Cancellable.class, "wakeupTask");
+	private final Cancellable checkTask =
+			context.mock(Cancellable.class, "checkTask");
+
+	private final MailboxProperties mailboxProperties =
+			getMailboxProperties(false, CLIENT_SUPPORTS);
+	private final long now = System.currentTimeMillis();
+	private final MailboxFolderId folderId = new MailboxFolderId(getRandomId());
+	private final ContactId contactId = getContactId();
+	private final MessageId ackedId = new MessageId(getRandomId());
+	private final MessageId sentId = new MessageId(getRandomId());
+	private final MessageId newMessageId = new MessageId(getRandomId());
+
+	private File testDir, tempFile;
+	private MailboxUploadWorker worker;
+
+	@Before
+	public void setUp() {
+		testDir = getTestDirectory();
+		tempFile = new File(testDir, "temp");
+		worker = new MailboxUploadWorker(ioExecutor, db, clock, taskScheduler,
+				eventBus, connectivityChecker, mailboxApiCaller, mailboxApi,
+				mailboxFileManager, mailboxProperties, folderId, contactId);
+	}
+
+	@After
+	public void tearDown() {
+		deleteTestDirectory(testDir);
+	}
+
+	@Test
+	public void testChecksForDataWhenStartedAndRemovesObserverWhenDestroyed()
+			throws Exception {
+		// When the worker is started it should check for data to send
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendNoDataWaiting();
+
+		worker.start();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testChecksConnectivityWhenStartedIfDataIsReady()
+			throws Exception {
+		Transaction recordTxn = new Transaction(null, false);
+
+		// When the worker is started it should check for data to send. As
+		// there's data ready to send immediately, the worker should start a
+		// connectivity check
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendAndStartConnectivityCheck();
+
+		worker.start();
+
+		// Create the temporary file so we can test that it gets deleted
+		assertTrue(testDir.mkdirs());
+		assertTrue(tempFile.createNewFile());
+
+		// When the connectivity check succeeds, the worker should write a file
+		// and start an upload task
+		expectRunTaskOnIoExecutor();
+		AtomicReference<ApiCall> upload = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createAndWriteTempFileForUpload(
+					with(contactId), with(any(OutgoingSessionRecord.class)));
+			will(new DoAllAction(
+					// Record some IDs as acked and sent
+					new ConsumeArgumentAction<>(OutgoingSessionRecord.class, 1,
+							record -> {
+								record.onAckSent(singletonList(ackedId));
+								record.onMessageSent(sentId);
+							}),
+					returnValue(tempFile)
+			));
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(upload, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the upload task runs, it should upload the file, record
+		// the acked/sent messages in the DB, and check for more data to send
+		context.checking(new DbExpectations() {{
+			oneOf(mailboxApi).addFile(mailboxProperties, folderId, tempFile);
+			oneOf(db).transaction(with(false), withDbRunnable(recordTxn));
+			oneOf(db).setAckSent(recordTxn, contactId, singletonList(ackedId));
+			oneOf(db).setMessagesSent(recordTxn, contactId,
+					singletonList(sentId), MAX_LATENCY);
+		}});
+		expectCheckForDataToSendNoDataWaiting();
+
+		assertFalse(upload.get().callApi());
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// The file should have been deleted
+		assertFalse(tempFile.exists());
+	}
+
+	@Test
+	public void testCancelsApiCallWhenDestroyed() throws Exception {
+		// When the worker is started it should check for data to send. As
+		// there's data ready to send immediately, the worker should start a
+		// connectivity check
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendAndStartConnectivityCheck();
+
+		worker.start();
+
+		// Create the temporary file so we can test that it gets deleted
+		assertTrue(testDir.mkdirs());
+		assertTrue(tempFile.createNewFile());
+
+		// When the connectivity check succeeds, the worker should write a file
+		// and start an upload task
+		expectRunTaskOnIoExecutor();
+		AtomicReference<ApiCall> upload = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createAndWriteTempFileForUpload(
+					with(contactId), with(any(OutgoingSessionRecord.class)));
+			will(new DoAllAction(
+					// Record some IDs as acked and sent
+					new ConsumeArgumentAction<>(OutgoingSessionRecord.class, 1,
+							record -> {
+								record.onAckSent(singletonList(ackedId));
+								record.onMessageSent(sentId);
+							}),
+					returnValue(tempFile)
+			));
+			oneOf(mailboxApiCaller).retryWithBackoff(with(any(ApiCall.class)));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(upload, ApiCall.class, 0),
+					returnValue(apiCall)
+			));
+		}});
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener and cancel the upload task
+		context.checking(new Expectations() {{
+			oneOf(apiCall).cancel();
+		}});
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// The file should have been deleted
+		assertFalse(tempFile.exists());
+
+		// If the upload task runs anyway (cancellation came too late), it
+		// should return early when it finds the state has changed
+		assertFalse(upload.get().callApi());
+	}
+
+	@Test
+	public void testSchedulesWakeupWhenStartedIfDataIsNotReady()
+			throws Exception {
+		// When the worker is started it should check for data to send. As
+		// the data isn't ready to send immediately, the worker should
+		// schedule a wakeup
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> wakeup = new AtomicReference<>();
+		expectCheckForDataToSendAndScheduleWakeup(wakeup);
+
+		worker.start();
+
+		// When the wakeup task runs it should check for data to send
+		expectCheckForDataToSendNoDataWaiting();
+
+		wakeup.get().run();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testCancelsWakeupIfDestroyedBeforeWakingUp() throws Exception {
+		// When the worker is started it should check for data to send. As
+		// the data isn't ready to send immediately, the worker should
+		// schedule a wakeup
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> wakeup = new AtomicReference<>();
+		expectCheckForDataToSendAndScheduleWakeup(wakeup);
+
+		worker.start();
+
+		// When the worker is destroyed it should cancel the wakeup and
+		// remove the connectivity observer and event listener
+		context.checking(new Expectations() {{
+			oneOf(wakeupTask).cancel();
+		}});
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// If the wakeup task runs anyway (cancellation came too late), it
+		// should return early without doing anything
+		wakeup.get().run();
+	}
+
+	@Test
+	public void testCancelsWakeupIfEventIsReceivedBeforeWakingUp()
+			throws Exception {
+		// When the worker is started it should check for data to send. As
+		// the data isn't ready to send immediately, the worker should
+		// schedule a wakeup
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> wakeup = new AtomicReference<>();
+		expectCheckForDataToSendAndScheduleWakeup(wakeup);
+
+		worker.start();
+
+		// Before the wakeup task runs, the worker receives an event that
+		// indicates new data may be available. The worker should cancel the
+		// wakeup task and schedule a check for new data after a short delay
+		AtomicReference<Runnable> check = new AtomicReference<>();
+		expectScheduleCheck(check, CHECK_DELAY_MS);
+		context.checking(new Expectations() {{
+			oneOf(wakeupTask).cancel();
+		}});
+
+		worker.eventOccurred(new MessageSharedEvent(newMessageId));
+
+		// If the wakeup task runs anyway (cancellation came too late), it
+		// should return early when it finds the state has changed
+		wakeup.get().run();
+
+		// Before the check task runs, the worker receives another event that
+		// indicates new data may be available. The event should be ignored,
+		// as a check for new data has already been scheduled
+		worker.eventOccurred(new MessageSharedEvent(newMessageId));
+
+		// When the check task runs, it should check for new data
+		expectCheckForDataToSendNoDataWaiting();
+
+		check.get().run();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	@Test
+	public void testCancelsCheckWhenDestroyed() throws Exception {
+		// When the worker is started it should check for data to send
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendNoDataWaiting();
+
+		worker.start();
+
+		// The worker receives an event that indicates new data may be
+		// available. The worker should schedule a check for new data after
+		// a short delay
+		AtomicReference<Runnable> check = new AtomicReference<>();
+		expectScheduleCheck(check, CHECK_DELAY_MS);
+
+		worker.eventOccurred(new MessageSharedEvent(newMessageId));
+
+		// When the worker is destroyed it should cancel the check and
+		// remove the connectivity observer and event listener
+		context.checking(new Expectations() {{
+			oneOf(checkTask).cancel();
+		}});
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+
+		// If the check runs anyway (cancellation came too late), it should
+		// return early when it finds the state has changed
+		check.get().run();
+	}
+
+	@Test
+	public void testRetriesAfterDelayIfExceptionOccursWhileWritingFile()
+			throws Exception {
+		// When the worker is started it should check for data to send. As
+		// there's data ready to send immediately, the worker should start a
+		// connectivity check
+		expectRunTaskOnIoExecutor();
+		expectCheckForDataToSendAndStartConnectivityCheck();
+
+		worker.start();
+
+		// When the connectivity check succeeds, the worker should try to
+		// write a file. This fails with an exception, so the worker should
+		// retry by scheduling a check for new data after a short delay
+		expectRunTaskOnIoExecutor();
+		AtomicReference<Runnable> check = new AtomicReference<>();
+		context.checking(new Expectations() {{
+			oneOf(mailboxFileManager).createAndWriteTempFileForUpload(
+					with(contactId), with(any(OutgoingSessionRecord.class)));
+			will(throwException(new IOException())); // Oh noes!
+		}});
+		expectScheduleCheck(check, RETRY_DELAY_MS);
+
+		worker.onConnectivityCheckSucceeded();
+
+		// When the check task runs it should check for new data
+		expectCheckForDataToSendNoDataWaiting();
+
+		check.get().run();
+
+		// When the worker is destroyed it should remove the connectivity
+		// observer and event listener
+		expectRemoveObserverAndListener();
+
+		worker.destroy();
+	}
+
+	private void expectRunTaskOnIoExecutor() {
+		context.checking(new Expectations() {{
+			oneOf(ioExecutor).execute(with(any(Runnable.class)));
+			will(new RunAction());
+		}});
+	}
+
+	private void expectCheckForDataToSendNoDataWaiting() throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).containsAcksToSend(txn, contactId);
+			will(returnValue(false));
+			oneOf(db).getNextSendTime(txn, contactId, MAX_LATENCY);
+			will(returnValue(Long.MAX_VALUE)); // No data waiting
+		}});
+	}
+
+	private void expectCheckForDataToSendAndScheduleWakeup(
+			AtomicReference<Runnable> wakeup) throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).containsAcksToSend(txn, contactId);
+			will(returnValue(false));
+			oneOf(db).getNextSendTime(txn, contactId, MAX_LATENCY);
+			will(returnValue(now + 1234L)); // Data waiting but not ready
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(taskScheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(1234L), with(MILLISECONDS));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(wakeup, Runnable.class, 0),
+					returnValue(wakeupTask)
+			));
+		}});
+	}
+
+	private void expectCheckForDataToSendAndStartConnectivityCheck()
+			throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(true), withDbRunnable(txn));
+			oneOf(db).containsAcksToSend(txn, contactId);
+			will(returnValue(false));
+			oneOf(db).getNextSendTime(txn, contactId, MAX_LATENCY);
+			will(returnValue(0L)); // Data ready to send
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(connectivityChecker).checkConnectivity(mailboxProperties,
+					worker);
+		}});
+	}
+
+	private void expectScheduleCheck(AtomicReference<Runnable> check,
+			long delay) {
+		context.checking(new Expectations() {{
+			oneOf(taskScheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(delay), with(MILLISECONDS));
+			will(new DoAllAction(
+					new CaptureArgumentAction<>(check, Runnable.class, 0),
+					returnValue(checkTask)
+			));
+		}});
+	}
+
+	private void expectRemoveObserverAndListener() {
+		context.checking(new Expectations() {{
+			oneOf(connectivityChecker).removeObserver(worker);
+			oneOf(eventBus).removeListener(worker);
+		}});
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/test/ConsumeArgumentAction.java

@@ -0,0 +1,32 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.Consumer;
+import org.hamcrest.Description;
+import org.jmock.api.Action;
+import org.jmock.api.Invocation;
+
+public class ConsumeArgumentAction<T> implements Action {
+
+	private final Class<T> capturedClass;
+	private final int index;
+	private final Consumer<T> consumer;
+
+	public ConsumeArgumentAction(Class<T> capturedClass, int index,
+			Consumer<T> consumer) {
+		this.capturedClass = capturedClass;
+		this.index = index;
+		this.consumer = consumer;
+	}
+
+	@Override
+	public Object invoke(Invocation invocation) {
+		consumer.accept(capturedClass.cast(invocation.getParameter(index)));
+		return null;
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendText("passes an argument to a consumer");
+	}
+
+}