Merge branch 'poller-refactoring' into 'master'

Poller refactoring, replace Timer with ScheduledExecutorService

* Replace Timer with ScheduledExecutorService (closes #258)
* Move automatic connection logic from PluginManager to Poller
* Reschedule polling when connections are opened or closed, making the poller more responsive to reductions in the polling interval


See merge request !180

briar-core/src/org/briarproject/plugins/PluginManagerImpl.java

@@ -3,18 +3,13 @@ package org.briarproject.plugins;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.ContactId;
 import org.briarproject.api.db.DbException;
-import org.briarproject.api.event.ConnectionClosedEvent;
-import org.briarproject.api.event.ContactStatusChangedEvent;
-import org.briarproject.api.event.Event;
 import org.briarproject.api.event.EventBus;
-import org.briarproject.api.event.EventListener;
 import org.briarproject.api.event.TransportDisabledEvent;
 import org.briarproject.api.event.TransportEnabledEvent;
 import org.briarproject.api.lifecycle.IoExecutor;
 import org.briarproject.api.lifecycle.Service;
 import org.briarproject.api.lifecycle.ServiceException;
 import org.briarproject.api.plugins.ConnectionManager;
-import org.briarproject.api.plugins.ConnectionRegistry;
 import org.briarproject.api.plugins.Plugin;
 import org.briarproject.api.plugins.PluginCallback;
 import org.briarproject.api.plugins.PluginConfig;
@@ -51,7 +46,7 @@ import javax.inject.Inject;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 
-class PluginManagerImpl implements PluginManager, Service, EventListener {
+class PluginManagerImpl implements PluginManager, Service {
 
 	private static final Logger LOG =
 			Logger.getLogger(PluginManagerImpl.class.getName());
@@ -59,9 +54,7 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 	private final Executor ioExecutor;
 	private final EventBus eventBus;
 	private final PluginConfig pluginConfig;
-	private final Poller poller;
 	private final ConnectionManager connectionManager;
-	private final ConnectionRegistry connectionRegistry;
 	private final SettingsManager settingsManager;
 	private final TransportPropertyManager transportPropertyManager;
 	private final UiCallback uiCallback;
@@ -71,18 +64,14 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 
 	@Inject
 	PluginManagerImpl(@IoExecutor Executor ioExecutor, EventBus eventBus,
-			PluginConfig pluginConfig, Poller poller,
-			ConnectionManager connectionManager,
-			ConnectionRegistry connectionRegistry,
+			PluginConfig pluginConfig, ConnectionManager connectionManager,
 			SettingsManager settingsManager,
 			TransportPropertyManager transportPropertyManager,
 			UiCallback uiCallback) {
 		this.ioExecutor = ioExecutor;
 		this.eventBus = eventBus;
 		this.pluginConfig = pluginConfig;
-		this.poller = poller;
 		this.connectionManager = connectionManager;
-		this.connectionRegistry = connectionRegistry;
 		this.settingsManager = settingsManager;
 		this.transportPropertyManager = transportPropertyManager;
 		this.uiCallback = uiCallback;
@@ -93,39 +82,53 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 
 	@Override
 	public void startService() throws ServiceException {
+		Collection<SimplexPluginFactory> simplexFactories =
+				pluginConfig.getSimplexFactories();
+		Collection<DuplexPluginFactory> duplexFactories =
+				pluginConfig.getDuplexFactories();
+		int numPlugins = simplexFactories.size() + duplexFactories.size();
+		CountDownLatch latch = new CountDownLatch(numPlugins);
 		// Instantiate and start the simplex plugins
 		LOG.info("Starting simplex plugins");
-		Collection<SimplexPluginFactory> sFactories =
-				pluginConfig.getSimplexFactories();
-		final CountDownLatch sLatch = new CountDownLatch(sFactories.size());
-		for (SimplexPluginFactory factory : sFactories)
-			ioExecutor.execute(new SimplexPluginStarter(factory, sLatch));
+		for (SimplexPluginFactory f : simplexFactories) {
+			TransportId t = f.getId();
+			SimplexPlugin s = f.createPlugin(new SimplexCallback(t));
+			if (s == null) {
+				if (LOG.isLoggable(WARNING))
+					LOG.warning("Could not create plugin for " + t);
+				latch.countDown();
+			} else {
+				plugins.put(t, s);
+				simplexPlugins.add(s);
+				ioExecutor.execute(new PluginStarter(s, latch));
+			}
+		}
 		// Instantiate and start the duplex plugins
 		LOG.info("Starting duplex plugins");
-		Collection<DuplexPluginFactory> dFactories =
-				pluginConfig.getDuplexFactories();
-		final CountDownLatch dLatch = new CountDownLatch(dFactories.size());
-		for (DuplexPluginFactory factory : dFactories)
-			ioExecutor.execute(new DuplexPluginStarter(factory, dLatch));
-		// Wait for the plugins to start
+		for (DuplexPluginFactory f : duplexFactories) {
+			TransportId t = f.getId();
+			DuplexPlugin d = f.createPlugin(new DuplexCallback(t));
+			if (d == null) {
+				if (LOG.isLoggable(WARNING))
+					LOG.warning("Could not create plugin for " + t);
+				latch.countDown();
+			} else {
+				plugins.put(t, d);
+				duplexPlugins.add(d);
+				ioExecutor.execute(new PluginStarter(d, latch));
+			}
+		}
+		// Wait for all the plugins to start
 		try {
-			sLatch.await();
-			dLatch.await();
+			latch.await();
 		} catch (InterruptedException e) {
 			throw new ServiceException(e);
 		}
-		// Listen for events
-		eventBus.addListener(this);
 	}
 
 	@Override
 	public void stopService() throws ServiceException {
-		// Stop listening for events
-		eventBus.removeListener(this);
-		// Stop the poller
-		LOG.info("Stopping poller");
-		poller.stop();
-		final CountDownLatch latch = new CountDownLatch(plugins.size());
+		CountDownLatch latch = new CountDownLatch(plugins.size());
 		// Stop the simplex plugins
 		LOG.info("Stopping simplex plugins");
 		for (SimplexPlugin plugin : simplexPlugins)
@@ -147,6 +150,16 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 		return plugins.get(t);
 	}
 
+	@Override
+	public Collection<SimplexPlugin> getSimplexPlugins() {
+		return Collections.unmodifiableList(simplexPlugins);
+	}
+
+	@Override
+	public Collection<DuplexPlugin> getDuplexPlugins() {
+		return Collections.unmodifiableList(duplexPlugins);
+	}
+
 	@Override
 	public Collection<DuplexPlugin> getInvitationPlugins() {
 		List<DuplexPlugin> supported = new ArrayList<DuplexPlugin>();
@@ -163,158 +176,32 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 		return Collections.unmodifiableList(supported);
 	}
 
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof ContactStatusChangedEvent) {
-			ContactStatusChangedEvent c = (ContactStatusChangedEvent) e;
-			if (c.isActive()) {
-				// Connect to the newly activated contact
-				connectToContact(c.getContactId());
-			}
-		} else if (e instanceof ConnectionClosedEvent) {
-			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
-			if (!c.isIncoming()) {
-				// Connect to the disconnected contact
-				connectToContact(c.getContactId(), c.getTransportId());
-			}
-		}
-	}
+	private class PluginStarter implements Runnable {
 
-	private void connectToContact(ContactId c) {
-		for (SimplexPlugin s : simplexPlugins)
-			if (s.shouldPoll()) connectToContact(c, s);
-		for (DuplexPlugin d : duplexPlugins)
-			if (d.shouldPoll()) connectToContact(c, d);
-	}
-
-	private void connectToContact(ContactId c, TransportId t) {
-		Plugin p = plugins.get(t);
-		if (p instanceof SimplexPlugin && p.shouldPoll())
-			connectToContact(c, (SimplexPlugin) p);
-		else if (p instanceof DuplexPlugin && p.shouldPoll())
-			connectToContact(c, (DuplexPlugin) p);
-	}
-
-	private void connectToContact(final ContactId c, final SimplexPlugin p) {
-		ioExecutor.execute(new Runnable() {
-			@Override
-			public void run() {
-				TransportId t = p.getId();
-				if (!connectionRegistry.isConnected(c, t)) {
-					TransportConnectionWriter w = p.createWriter(c);
-					if (w != null)
-						connectionManager.manageOutgoingConnection(c, t, w);
-				}
-			}
-		});
-	}
-
-	private void connectToContact(final ContactId c, final DuplexPlugin p) {
-		ioExecutor.execute(new Runnable() {
-			@Override
-			public void run() {
-				TransportId t = p.getId();
-				if (!connectionRegistry.isConnected(c, t)) {
-					DuplexTransportConnection d = p.createConnection(c);
-					if (d != null)
-						connectionManager.manageOutgoingConnection(c, t, d);
-				}
-			}
-		});
-	}
-
-	private class SimplexPluginStarter implements Runnable {
-
-		private final SimplexPluginFactory factory;
+		private final Plugin plugin;
 		private final CountDownLatch latch;
 
-		private SimplexPluginStarter(SimplexPluginFactory factory,
-				CountDownLatch latch) {
-			this.factory = factory;
+		private PluginStarter(Plugin plugin, CountDownLatch latch) {
+			this.plugin = plugin;
 			this.latch = latch;
 		}
 
 		@Override
 		public void run() {
 			try {
-				TransportId id = factory.getId();
-				SimplexCallback callback = new SimplexCallback(id);
-				SimplexPlugin plugin = factory.createPlugin(callback);
-				if (plugin == null) {
-					if (LOG.isLoggable(INFO)) {
-						String name = factory.getClass().getSimpleName();
-						LOG.info(name + " did not create a plugin");
-					}
-					return;
-				}
 				try {
 					long start = System.currentTimeMillis();
 					boolean started = plugin.start();
 					long duration = System.currentTimeMillis() - start;
 					if (started) {
-						plugins.put(id, plugin);
-						simplexPlugins.add(plugin);
 						if (LOG.isLoggable(INFO)) {
-							String name = plugin.getClass().getSimpleName();
-							LOG.info("Starting " + name + " took " +
-									duration + " ms");
+							LOG.info("Starting plugin " + plugin.getId()
+									+ " took " + duration + " ms");
 						}
 					} else {
 						if (LOG.isLoggable(WARNING)) {
-							String name = plugin.getClass().getSimpleName();
-							LOG.warning(name + " did not start");
-						}
-					}
-				} catch (IOException e) {
-					if (LOG.isLoggable(WARNING))
-						LOG.log(WARNING, e.toString(), e);
-				}
-			} finally {
-				latch.countDown();
-			}
-		}
-	}
-
-	private class DuplexPluginStarter implements Runnable {
-
-		private final DuplexPluginFactory factory;
-		private final CountDownLatch latch;
-
-		private DuplexPluginStarter(DuplexPluginFactory factory,
-				CountDownLatch latch) {
-			this.factory = factory;
-			this.latch = latch;
-		}
-
-		@Override
-		public void run() {
-			try {
-				TransportId id = factory.getId();
-				DuplexCallback callback = new DuplexCallback(id);
-				DuplexPlugin plugin = factory.createPlugin(callback);
-				if (plugin == null) {
-					if (LOG.isLoggable(INFO)) {
-						String name = factory.getClass().getSimpleName();
-						LOG.info(name + " did not create a plugin");
-					}
-					return;
-				}
-				try {
-					long start = System.currentTimeMillis();
-					boolean started = plugin.start();
-					long duration = System.currentTimeMillis() - start;
-					if (started) {
-						plugins.put(id, plugin);
-						duplexPlugins.add(plugin);
-						if (LOG.isLoggable(INFO)) {
-							String name = plugin.getClass().getSimpleName();
-							LOG.info("Starting " + name + " took " +
-									duration + " ms");
-						}
-					} else {
-						if (LOG.isLoggable(WARNING)) {
-							String name = plugin.getClass().getSimpleName();
-							LOG.warning(name + " did not start");
+							LOG.warning("Plugin" + plugin.getId()
+									+ " did not start");
 						}
 					}
 				} catch (IOException e) {
@@ -344,8 +231,8 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 				plugin.stop();
 				long duration = System.currentTimeMillis() - start;
 				if (LOG.isLoggable(INFO)) {
-					String name = plugin.getClass().getSimpleName();
-					LOG.info("Stopping " + name + " took " + duration + " ms");
+					LOG.info("Stopping plugin " + plugin.getId()
+							+ " took " + duration + " ms");
 				}
 			} catch (IOException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
@@ -431,8 +318,6 @@ class PluginManagerImpl implements PluginManager, Service, EventListener {
 		@Override
 		public void transportEnabled() {
 			eventBus.broadcast(new TransportEnabledEvent(id));
-			Plugin p = plugins.get(id);
-			if (p != null) poller.pollNow(p);
 		}
 
 		@Override

briar-core/src/org/briarproject/plugins/PluginsModule.java

@@ -7,14 +7,11 @@ import org.briarproject.api.plugins.BackoffFactory;
 import org.briarproject.api.plugins.ConnectionManager;
 import org.briarproject.api.plugins.ConnectionRegistry;
 import org.briarproject.api.plugins.PluginManager;
-import org.briarproject.api.sync.SyncSessionFactory;
-import org.briarproject.api.system.Timer;
-import org.briarproject.api.transport.KeyManager;
-import org.briarproject.api.transport.StreamReaderFactory;
-import org.briarproject.api.transport.StreamWriterFactory;
+import org.briarproject.api.system.Clock;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
+import java.util.concurrent.ScheduledExecutorService;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -28,6 +25,8 @@ public class PluginsModule {
 	public static class EagerSingletons {
 		@Inject
 		PluginManager pluginManager;
+		@Inject
+		Poller poller;
 	}
 
 	@Provides
@@ -36,33 +35,35 @@ public class PluginsModule {
 	}
 
 	@Provides
+	@Singleton
 	Poller providePoller(@IoExecutor Executor ioExecutor,
-			ConnectionRegistry connectionRegistry, SecureRandom random,
-			Timer timer) {
-		return new PollerImpl(ioExecutor, connectionRegistry, random, timer);
+			ScheduledExecutorService scheduler,
+			ConnectionManager connectionManager,
+			ConnectionRegistry connectionRegistry, PluginManager pluginManager,
+			SecureRandom random, Clock clock, EventBus eventBus) {
+		Poller poller = new Poller(ioExecutor, scheduler, connectionManager,
+				connectionRegistry, pluginManager, random, clock);
+		eventBus.addListener(poller);
+		return poller;
 	}
 
 	@Provides
+	@Singleton
 	ConnectionManager provideConnectionManager(
-			@IoExecutor Executor ioExecutor, KeyManager keyManager,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			ConnectionRegistry connectionRegistry) {
-		return new ConnectionManagerImpl(ioExecutor, keyManager,
-				streamReaderFactory, streamWriterFactory, syncSessionFactory,
-				connectionRegistry);
+			ConnectionManagerImpl connectionManager) {
+		return connectionManager;
 	}
 
 	@Provides
 	@Singleton
-	ConnectionRegistry provideConnectionRegistry(EventBus eventBus) {
-		return new ConnectionRegistryImpl(eventBus);
+	ConnectionRegistry provideConnectionRegistry(
+			ConnectionRegistryImpl connectionRegistry) {
+		return connectionRegistry;
 	}
 
 	@Provides
 	@Singleton
-	PluginManager getPluginManager(LifecycleManager lifecycleManager,
+	PluginManager providePluginManager(LifecycleManager lifecycleManager,
 			PluginManagerImpl pluginManager) {
 		lifecycleManager.registerService(pluginManager);
 		return pluginManager;

briar-core/src/org/briarproject/plugins/Poller.java

@@ -1,12 +1,203 @@
 package org.briarproject.plugins;
 
+import org.briarproject.api.TransportId;
+import org.briarproject.api.contact.ContactId;
+import org.briarproject.api.event.ConnectionClosedEvent;
+import org.briarproject.api.event.ConnectionOpenedEvent;
+import org.briarproject.api.event.ContactStatusChangedEvent;
+import org.briarproject.api.event.Event;
+import org.briarproject.api.event.EventListener;
+import org.briarproject.api.event.TransportEnabledEvent;
+import org.briarproject.api.lifecycle.IoExecutor;
+import org.briarproject.api.plugins.ConnectionManager;
+import org.briarproject.api.plugins.ConnectionRegistry;
 import org.briarproject.api.plugins.Plugin;
+import org.briarproject.api.plugins.PluginManager;
+import org.briarproject.api.plugins.TransportConnectionWriter;
+import org.briarproject.api.plugins.duplex.DuplexPlugin;
+import org.briarproject.api.plugins.duplex.DuplexTransportConnection;
+import org.briarproject.api.plugins.simplex.SimplexPlugin;
+import org.briarproject.api.system.Clock;
 
-interface Poller {
+import java.security.SecureRandom;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.logging.Logger;
 
-	/** Tells the poller to poll the given plugin immediately. */
-	void pollNow(Plugin p);
+import javax.inject.Inject;
 
-	/** Stops the poller. */
-	void stop();
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.logging.Level.INFO;
+
+class Poller implements EventListener {
+
+	private static final Logger LOG = Logger.getLogger(Poller.class.getName());
+
+	private final Executor ioExecutor;
+	private final ScheduledExecutorService scheduler;
+	private final ConnectionManager connectionManager;
+	private final ConnectionRegistry connectionRegistry;
+	private final PluginManager pluginManager;
+	private final SecureRandom random;
+	private final Clock clock;
+	private final Lock lock;
+	private final Map<TransportId, PollTask> tasks; // Locking: lock
+
+	@Inject
+	Poller(@IoExecutor Executor ioExecutor, ScheduledExecutorService scheduler,
+			ConnectionManager connectionManager,
+			ConnectionRegistry connectionRegistry, PluginManager pluginManager,
+			SecureRandom random, Clock clock) {
+		this.ioExecutor = ioExecutor;
+		this.scheduler = scheduler;
+		this.connectionManager = connectionManager;
+		this.connectionRegistry = connectionRegistry;
+		this.pluginManager = pluginManager;
+		this.random = random;
+		this.clock = clock;
+		lock = new ReentrantLock();
+		tasks = new HashMap<TransportId, PollTask>();
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof ContactStatusChangedEvent) {
+			ContactStatusChangedEvent c = (ContactStatusChangedEvent) e;
+			if (c.isActive()) {
+				// Connect to the newly activated contact
+				connectToContact(c.getContactId());
+			}
+		} else if (e instanceof ConnectionClosedEvent) {
+			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
+			// Reschedule polling, the polling interval may have decreased
+			reschedule(c.getTransportId());
+			if (!c.isIncoming()) {
+				// Connect to the disconnected contact
+				connectToContact(c.getContactId(), c.getTransportId());
+			}
+		} else if (e instanceof ConnectionOpenedEvent) {
+			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
+			// Reschedule polling, the polling interval may have decreased
+			reschedule(c.getTransportId());
+		} else if (e instanceof TransportEnabledEvent) {
+			TransportEnabledEvent t = (TransportEnabledEvent) e;
+			// Poll the newly enabled transport
+			pollNow(t.getTransportId());
+		}
+	}
+
+	private void connectToContact(ContactId c) {
+		for (SimplexPlugin s : pluginManager.getSimplexPlugins())
+			if (s.shouldPoll()) connectToContact(c, s);
+		for (DuplexPlugin d : pluginManager.getDuplexPlugins())
+			if (d.shouldPoll()) connectToContact(c, d);
+	}
+
+	private void connectToContact(ContactId c, TransportId t) {
+		Plugin p = pluginManager.getPlugin(t);
+		if (p instanceof SimplexPlugin && p.shouldPoll())
+			connectToContact(c, (SimplexPlugin) p);
+		else if (p instanceof DuplexPlugin && p.shouldPoll())
+			connectToContact(c, (DuplexPlugin) p);
+	}
+
+	private void connectToContact(final ContactId c, final SimplexPlugin p) {
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				TransportId t = p.getId();
+				if (!connectionRegistry.isConnected(c, t)) {
+					TransportConnectionWriter w = p.createWriter(c);
+					if (w != null)
+						connectionManager.manageOutgoingConnection(c, t, w);
+				}
+			}
+		});
+	}
+
+	private void connectToContact(final ContactId c, final DuplexPlugin p) {
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				TransportId t = p.getId();
+				if (!connectionRegistry.isConnected(c, t)) {
+					DuplexTransportConnection d = p.createConnection(c);
+					if (d != null)
+						connectionManager.manageOutgoingConnection(c, t, d);
+				}
+			}
+		});
+	}
+
+	private void reschedule(TransportId t) {
+		Plugin p = pluginManager.getPlugin(t);
+		if (p.shouldPoll()) schedule(p, p.getPollingInterval(), false);
+	}
+
+	private void pollNow(TransportId t) {
+		Plugin p = pluginManager.getPlugin(t);
+		// Randomise next polling interval
+		if (p.shouldPoll()) schedule(p, 0, true);
+	}
+
+	private void schedule(Plugin p, int delay, boolean randomiseNext) {
+		// Replace any later scheduled task for this plugin
+		long due = clock.currentTimeMillis() + delay;
+		TransportId t = p.getId();
+		lock.lock();
+		try {
+			PollTask scheduled = tasks.get(t);
+			if (scheduled == null || due < scheduled.due) {
+				PollTask task = new PollTask(p, due, randomiseNext);
+				tasks.put(t, task);
+				scheduler.schedule(task, delay, MILLISECONDS);
+			}
+		} finally {
+			lock.unlock();
+		}
+	}
+
+	private void poll(final Plugin p) {
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				TransportId t = p.getId();
+				if (LOG.isLoggable(INFO)) LOG.info("Polling plugin " + t);
+				p.poll(connectionRegistry.getConnectedContacts(t));
+			}
+		});
+	}
+
+	private class PollTask implements Runnable {
+
+		private final Plugin plugin;
+		private final long due;
+		private final boolean randomiseNext;
+
+		private PollTask(Plugin plugin, long due, boolean randomiseNext) {
+			this.plugin = plugin;
+			this.due = due;
+			this.randomiseNext = randomiseNext;
+		}
+
+		@Override
+		public void run() {
+			lock.lock();
+			try {
+				TransportId t = plugin.getId();
+				if (tasks.get(t) != this) return; // Replaced by another task
+				tasks.remove(t);
+			} finally {
+				lock.unlock();
+			}
+			int delay = plugin.getPollingInterval();
+			if (randomiseNext) delay = (int) (delay * random.nextDouble());
+			schedule(plugin, delay, false);
+			poll(plugin);
+		}
+	}
 }

briar-core/src/org/briarproject/plugins/PollerImpl.java

@@ -1,92 +0,0 @@
-package org.briarproject.plugins;
-
-import org.briarproject.api.TransportId;
-import org.briarproject.api.lifecycle.IoExecutor;
-import org.briarproject.api.plugins.ConnectionRegistry;
-import org.briarproject.api.plugins.Plugin;
-import org.briarproject.api.system.Timer;
-
-import java.security.SecureRandom;
-import java.util.Map;
-import java.util.TimerTask;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.inject.Inject;
-
-import static java.util.logging.Level.INFO;
-
-class PollerImpl implements Poller {
-
-	private static final Logger LOG =
-			Logger.getLogger(PollerImpl.class.getName());
-
-	private final Executor ioExecutor;
-	private final ConnectionRegistry connectionRegistry;
-	private final SecureRandom random;
-	private final Timer timer;
-	private final Map<TransportId, PollTask> tasks;
-
-	@Inject
-	PollerImpl(@IoExecutor Executor ioExecutor,
-			ConnectionRegistry connectionRegistry, SecureRandom random,
-			Timer timer) {
-		this.ioExecutor = ioExecutor;
-		this.connectionRegistry = connectionRegistry;
-		this.random = random;
-		this.timer = timer;
-		tasks = new ConcurrentHashMap<TransportId, PollTask>();
-	}
-
-	@Override
-	public void stop() {
-		timer.cancel();
-	}
-
-	@Override
-	public void pollNow(Plugin p) {
-		// Randomise next polling interval
-		if (p.shouldPoll()) schedule(p, 0, true);
-	}
-
-	private void schedule(Plugin p, int interval, boolean randomiseNext) {
-		// Replace any previously scheduled task for this plugin
-		PollTask task = new PollTask(p, randomiseNext);
-		PollTask replaced = tasks.put(p.getId(), task);
-		if (replaced != null) replaced.cancel();
-		timer.schedule(task, interval);
-	}
-
-	private void poll(final Plugin p) {
-		ioExecutor.execute(new Runnable() {
-			@Override
-			public void run() {
-				if (LOG.isLoggable(INFO))
-					LOG.info("Polling " + p.getClass().getSimpleName());
-				p.poll(connectionRegistry.getConnectedContacts(p.getId()));
-			}
-		});
-	}
-
-	private class PollTask extends TimerTask {
-
-		private final Plugin plugin;
-		private final boolean randomiseNext;
-
-		private PollTask(Plugin plugin, boolean randomiseNext) {
-			this.plugin = plugin;
-			this.randomiseNext = randomiseNext;
-		}
-
-		@Override
-		public void run() {
-			tasks.remove(plugin.getId());
-			int interval = plugin.getPollingInterval();
-			if (randomiseNext)
-				interval = (int) (interval * random.nextDouble());
-			schedule(plugin, interval, false);
-			poll(plugin);
-		}
-	}
-}