Issue #6728 - QUIC and HTTP/3

- Moved ExecutionStrategy from ServerQuicConnection to QuicConnection.
  For the server the produced task is declared as BLOCKING, but for the
  client the produced task is NON_BLOCKING.
- Fixed race condition in QuicSession.process(...).
- Updated quic-quiche pom.xml.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>

jetty-client/src/main/java/org/eclipse/jetty/client/AbstractConnectorHttpClientTransport.java

@@ -33,7 +33,7 @@ public abstract class AbstractConnectorHttpClientTransport extends AbstractHttpC
     protected AbstractConnectorHttpClientTransport(ClientConnector connector)
     {
         this.connector = Objects.requireNonNull(connector);
-        addBean(connector, false);
+        addBean(connector);
     }
 
     public ClientConnector getClientConnector()

jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/api/Stream.java

@@ -73,17 +73,16 @@ public interface Stream
      * that the end of the read side of the stream has not yet been reached, which
      * may happen in these cases:</p>
      * <ul>
-     *   <li>not all the bytes have been received so far, and a further attempt
+     *   <li>not all the bytes have been received so far, for example the remote
-     *   to call this method returns {@code null} because the rest of the bytes
+     *   peer did not send them yet, or they are in-flight</li>
-     *   are not yet available (for example, the remote peer did not send them
-     *   yet, or they are in-flight)</li>
      *   <li>all the bytes have been received, but there is a trailer HEADERS
      *   frame to be received to indicate the end of the read side of the
-     *   stream.</li>
+     *   stream</li>
      * </ul>
      * <p>When the returned {@link Stream.Data} object is not {@code null},
-     * applications <em>must</em> call {@link Stream.Data#complete()} to
+     * applications <em>must</em> call, either immediately or later (possibly
-     * notify the implementation that the bytes have been processed.</p>
+     * asynchronously) {@link Stream.Data#complete()} to notify the
+     * implementation that the bytes have been processed.</p>
      * <p>{@link Stream.Data} objects may be stored away for later, asynchronous,
      * processing (for example, to process them only when all of them have been
      * received).</p>
@@ -163,8 +162,8 @@ public interface Stream
 
         /**
          * <p>Callback method invoked if the application has expressed
-         * {@link Stream#demand() demand} for content, and if there is
+         * {@link Stream#demand() demand} for content, and if there may
-         * content available.</p>
+         * be content available.</p>
          * <p>A server application that wishes to handle request content
          * should typically call {@link Stream#demand()} from
          * {@link Session.Server.Listener#onRequest(Stream, HeadersFrame)}.</p>
@@ -175,7 +174,7 @@ public interface Stream
          * cancelled; applications that implement this method should read
          * content calling {@link Stream#readData()}, and call
          * {@link Stream#demand()} to signal to the implementation to call
-         * again this method when there is more content available.</p>
+         * again this method when there may be more content available.</p>
          * <p>Only one thread at a time invokes this method, although it
          * may not be the same thread across different invocations.</p>
          * <p>It is always guaranteed that invoking {@link Stream#demand()}

jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/AbstractClientServerTest.java

@@ -116,6 +116,7 @@ public class AbstractClientServerTest
     @AfterEach
     public void dispose()
     {
+        LifeCycle.stop(http3Client);
         LifeCycle.stop(httpClient);
         LifeCycle.stop(server);
     }

jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/DataDemandTest.java

@@ -525,16 +525,36 @@ public class DataDemandTest extends AbstractClientServerTest
                 stream.demand();
                 return new Stream.Listener()
                 {
+                    private boolean firstData;
+                    private boolean nullData;
+
                     @Override
                     public void onDataAvailable(Stream stream)
                     {
+                        while (!firstData)
+                        {
+                            Stream.Data data = stream.readData();
+                            if (data == null)
+                                continue;
+                            firstData = true;
+                            break;
+                        }
+
+                        if (!nullData)
+                        {
+                            assertNull(stream.readData());
+                            // Verify that readData() is idempotent.
+                            assertNull(stream.readData());
+                            nullData = true;
+                            nullDataLatch.countDown();
+                            stream.demand();
+                            return;
+                        }
+
                         Stream.Data data = stream.readData();
                         if (data == null)
                         {
-                            // Second attempt to read still has no data, should be idempotent.
-                            assertNull(stream.readData());
                             stream.demand();
-                            nullDataLatch.countDown();
                         }
                         else
                         {
@@ -552,12 +572,13 @@ public class DataDemandTest extends AbstractClientServerTest
         Session.Client session = newSession(new Session.Client.Listener() {});
 
         HeadersFrame request = new HeadersFrame(newRequest("/"), false);
-        Stream stream = session.newRequest(request, new Stream.Listener() {}).get(5, TimeUnit.SECONDS);
+        Stream stream = session.newRequest(request, new Stream.Listener() {})
+            .get(5, TimeUnit.SECONDS);
 
         // Send a first chunk to trigger reads.
         stream.data(new DataFrame(ByteBuffer.allocate(16), false));
 
-        assertTrue(nullDataLatch.await(555, TimeUnit.SECONDS));
+        assertTrue(nullDataLatch.await(5, TimeUnit.SECONDS));
 
         stream.data(new DataFrame(ByteBuffer.allocate(4096), true));
 

jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/GoAwayTest.java

@@ -1177,7 +1177,8 @@ public class GoAwayTest extends AbstractClientServerTest
 
         assertTrue(settingsLatch.await(5, TimeUnit.SECONDS));
 
-        http3Client.stop();
+        // Stopping the HttpClient will also stop the HTTP3Client.
+        httpClient.stop();
 
         assertTrue(serverGoAwayLatch.await(5, TimeUnit.SECONDS));
         assertTrue(serverDisconnectLatch.await(5, TimeUnit.SECONDS));

jetty-http3/http3-tests/src/test/java/org/eclipse/jetty/http3/tests/HttpClientTransportOverHTTP3Test.java

@@ -39,7 +39,7 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 public class HttpClientTransportOverHTTP3Test extends AbstractClientServerTest
 {
     @Test
-    public void testRequestHasHTTP2Version() throws Exception
+    public void testRequestHasHTTP3Version() throws Exception
     {
         start(new AbstractHandler()
         {

jetty-quic/quic-client/src/main/java/org/eclipse/jetty/quic/client/ClientProtocolSession.java

@@ -16,6 +16,7 @@ package org.eclipse.jetty.quic.client;
 import org.eclipse.jetty.quic.common.ProtocolSession;
 import org.eclipse.jetty.quic.common.QuicStreamEndPoint;
 import org.eclipse.jetty.quic.common.StreamType;
+import org.eclipse.jetty.util.thread.Invocable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -23,6 +24,8 @@ public class ClientProtocolSession extends ProtocolSession
 {
     private static final Logger LOG = LoggerFactory.getLogger(ClientProtocolSession.class);
 
+    private final Runnable producer = Invocable.from(Invocable.InvocationType.NON_BLOCKING, this::produce);
+
     public ClientProtocolSession(ClientQuicSession session)
     {
         super(session);
@@ -49,6 +52,12 @@ public class ClientProtocolSession extends ProtocolSession
         getOrCreateStreamEndPoint(streamId, this::configureProtocolEndPoint);
     }
 
+    @Override
+    public Runnable getProducer()
+    {
+        return producer;
+    }
+
     @Override
     protected boolean onReadable(long readableStreamId)
     {

jetty-quic/quic-client/src/main/java/org/eclipse/jetty/quic/client/ClientQuicConnection.java

@@ -112,18 +112,6 @@ public class ClientQuicConnection extends QuicConnection
         }
     }
 
-    @Override
-    public void onFillable()
-    {
-        while (true)
-        {
-            Runnable task = receiveAndProcess();
-            if (task == null)
-                break;
-            task.run();
-        }
-    }
-
     @Override
     protected QuicSession createSession(SocketAddress remoteAddress, ByteBuffer cipherBuffer) throws IOException
     {

jetty-quic/quic-client/src/test/java/org/eclipse/jetty/quic/client/End2EndClientTest.java

@@ -123,7 +123,7 @@ public class End2EndClientTest
     {
         for (int i = 0; i < 1000; i++)
         {
-            ContentResponse response = client.GET("https://localhost:" + connector.getLocalPort());
+            ContentResponse response = client.GET("https://localhost:" + connector.getLocalPort() + "/" + i);
             assertThat(response.getStatus(), is(200));
             String contentAsString = response.getContentAsString();
             assertThat(contentAsString, is(responseContent));
@@ -137,11 +137,12 @@ public class End2EndClientTest
         CompletableFuture<?>[] futures = new CompletableFuture[count];
         for (int i = 0; i < count; ++i)
         {
+            String path = "/" + i;
             futures[i] = CompletableFuture.runAsync(() ->
             {
                 try
                 {
-                    ContentResponse response = client.GET("https://localhost:" + connector.getLocalPort());
+                    ContentResponse response = client.GET("https://localhost:" + connector.getLocalPort() + path);
                     assertThat(response.getStatus(), is(200));
                     String contentAsString = response.getContentAsString();
                     assertThat(contentAsString, is(responseContent));

jetty-quic/quic-common/src/main/java/org/eclipse/jetty/quic/common/ProtocolSession.java

@@ -49,7 +49,9 @@ public abstract class ProtocolSession extends ContainerLifeCycle
         return session;
     }
 
-    public void process()
+    public abstract Runnable getProducer();
+
+    public void produce()
     {
         if (LOG.isDebugEnabled())
             LOG.debug("processing {}", this);
@@ -76,7 +78,10 @@ public abstract class ProtocolSession extends ContainerLifeCycle
         List<Long> writableStreamIds = session.getWritableStreamIds();
         if (LOG.isDebugEnabled())
             LOG.debug("writable stream ids: {}", writableStreamIds);
-        writableStreamIds.forEach(this::onWritable);
+        for (long writableStreamId : writableStreamIds)
+        {
+            onWritable(writableStreamId);
+        }
     }
 
     protected void onWritable(long writableStreamId)
@@ -97,7 +102,8 @@ public abstract class ProtocolSession extends ContainerLifeCycle
         boolean result = false;
         for (long readableStreamId : readableStreamIds)
         {
-            result = result || onReadable(readableStreamId);
+            // Bit-wise "or" because we do not want onReadable() to be short-circuited.
+            result |= onReadable(readableStreamId);
         }
         return result;
     }
@@ -154,7 +160,7 @@ public abstract class ProtocolSession extends ContainerLifeCycle
         public void offer(Runnable task)
         {
             if (LOG.isDebugEnabled())
-                LOG.debug("enqueuing task {} on {}", task, ProtocolSession.this);
+                LOG.debug("enqueuing stream task {} on {}", task, ProtocolSession.this);
             try (AutoLock l = lock.lock())
             {
                 tasks.offer(task);
@@ -174,7 +180,7 @@ public abstract class ProtocolSession extends ContainerLifeCycle
         {
             Runnable task = poll();
             if (LOG.isDebugEnabled())
-                LOG.debug("dequeued existing task {} on {}", task, ProtocolSession.this);
+                LOG.debug("dequeued existing stream task {} on {}", task, ProtocolSession.this);
             if (task != null)
                 return task;
 
@@ -185,7 +191,7 @@ public abstract class ProtocolSession extends ContainerLifeCycle
 
                 task = poll();
                 if (LOG.isDebugEnabled())
-                    LOG.debug("dequeued produced task {} on {}", task, ProtocolSession.this);
+                    LOG.debug("dequeued produced stream task {} on {}", task, ProtocolSession.this);
                 if (task != null)
                     return task;
 
@@ -197,7 +203,6 @@ public abstract class ProtocolSession extends ContainerLifeCycle
             if (closeInfo != null)
                 onClose(closeInfo.error(), closeInfo.reason());
 
-            getQuicSession().processingComplete();
             return null;
         }
     }

jetty-quic/quic-common/src/main/java/org/eclipse/jetty/quic/common/QuicConnection.java

@@ -38,7 +38,9 @@ import org.eclipse.jetty.util.Callback;
 import org.eclipse.jetty.util.IteratingCallback;
 import org.eclipse.jetty.util.component.LifeCycle;
 import org.eclipse.jetty.util.thread.AutoLock;
+import org.eclipse.jetty.util.thread.ExecutionStrategy;
 import org.eclipse.jetty.util.thread.Scheduler;
+import org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -58,6 +60,7 @@ public abstract class QuicConnection extends AbstractConnection
     private final AtomicBoolean closed = new AtomicBoolean();
     private final Scheduler scheduler;
     private final ByteBufferPool byteBufferPool;
+    private final AdaptiveExecutionStrategy strategy;
     private final Flusher flusher = new Flusher();
     private int outputBufferSize = 2048;
     private boolean useInputDirectByteBuffers = true;
@@ -68,6 +71,7 @@ public abstract class QuicConnection extends AbstractConnection
         super(endPoint, executor);
         this.scheduler = scheduler;
         this.byteBufferPool = byteBufferPool;
+        this.strategy = new AdaptiveExecutionStrategy(new QuicProducer(), getExecutor());
     }
 
     public Scheduler getScheduler()
@@ -131,11 +135,33 @@ public abstract class QuicConnection extends AbstractConnection
             listeners.remove((QuicSession.Listener)listener);
     }
 
-    public abstract void onFillable();
+    @Override
+    public void onOpen()
+    {
+        super.onOpen();
+        LifeCycle.start(strategy);
+    }
+
+    @Override
+    public void onClose(Throwable cause)
+    {
+        LifeCycle.stop(strategy);
+        super.onClose(cause);
+    }
+
+    public void onFillable()
+    {
+        produce();
+    }
 
     @Override
     public abstract boolean onIdleExpired();
 
+    public void produce()
+    {
+        strategy.produce();
+    }
+
     @Override
     public void close()
     {
@@ -172,12 +198,11 @@ public abstract class QuicConnection extends AbstractConnection
     {
         try
         {
-            if (isFillInterested())
+            boolean interested = isFillInterested();
-            {
+            if (LOG.isDebugEnabled())
-                if (LOG.isDebugEnabled())
+                LOG.debug("receiveAndProcess() interested={}", interested);
-                    LOG.debug("receiveAndProcess() idle");
+            if (interested)
                 return null;
-            }
 
             ByteBuffer cipherBuffer = byteBufferPool.acquire(getInputBufferSize(), isUseInputDirectByteBuffers());
             while (true)
@@ -249,7 +274,7 @@ public abstract class QuicConnection extends AbstractConnection
                     LOG.debug("packet is for existing session {}, processing {} bytes", session, cipherBuffer.remaining());
                 Runnable task = session.process(remoteAddress, cipherBuffer);
                 if (LOG.isDebugEnabled())
-                    LOG.debug("produced task {} on {}", task, session);
+                    LOG.debug("produced session task {} on {}", task, this);
                 if (task != null)
                     return task;
             }
@@ -263,6 +288,15 @@ public abstract class QuicConnection extends AbstractConnection
         }
     }
 
+    private class QuicProducer implements ExecutionStrategy.Producer
+    {
+        @Override
+        public Runnable produce()
+        {
+            return receiveAndProcess();
+        }
+    }
+
     private class Flusher extends IteratingCallback
     {
         private final AutoLock lock = new AutoLock();

jetty-quic/quic-common/src/main/java/org/eclipse/jetty/quic/common/QuicSession.java

@@ -25,7 +25,6 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Consumer;
 
@@ -59,7 +58,6 @@ public abstract class QuicSession extends ContainerLifeCycle
 
     private final AtomicLong[] ids = new AtomicLong[StreamType.values().length];
     private final ConcurrentMap<Long, QuicStreamEndPoint> endPoints = new ConcurrentHashMap<>();
-    private final AtomicBoolean processing = new AtomicBoolean();
     private final Executor executor;
     private final Scheduler scheduler;
     private final ByteBufferPool byteBufferPool;
@@ -297,7 +295,7 @@ public abstract class QuicSession extends ContainerLifeCycle
         if (accepted != remaining)
             throw new IllegalStateException();
 
-        if (quicheConnection.isConnectionEstablished())
+        if (isConnectionEstablished())
         {
             // HTTP/1.1
             // client1 -- sockEP1 -- H1Connection
@@ -330,10 +328,9 @@ public abstract class QuicSession extends ContainerLifeCycle
                 addManaged(session);
             }
 
-            boolean process = processing.compareAndSet(false, true);
             if (LOG.isDebugEnabled())
-                LOG.debug("processing={} on {}", process, session);
+                LOG.debug("processing {}", session);
-            return process ? session::process : null;
+            return session.getProducer();
         }
         else
         {
@@ -342,13 +339,6 @@ public abstract class QuicSession extends ContainerLifeCycle
         }
     }
 
-    void processingComplete()
-    {
-        if (LOG.isDebugEnabled())
-            LOG.debug("processing complete on {}", protocolSession);
-        processing.set(false);
-    }
-
     // TODO: this is ugly, is there a better solution?
     protected Runnable pollTask()
     {

jetty-quic/quic-common/src/main/java/org/eclipse/jetty/quic/common/QuicStreamEndPoint.java

@@ -214,6 +214,19 @@ public class QuicStreamEndPoint extends AbstractEndPoint
      */
     public boolean onReadable()
     {
+        // TODO: there is a race condition here.
+        //  Thread T1 enters this method and sees that this endPoint
+        //  is not interested, so it does not call onFillable().
+        //  Thread T2 is in fillInterested() about to set interest.
+        //  When this happens, this endPoint will miss a notification
+        //  that there is data to read.
+        //  The race condition is fixed by always calling produce()
+        //  from fillInterested() methods below.
+
+        // TODO: an alternative way of avoid the race would be to emulate an NIO style
+        //  notification, where onReadable() gets called only if there is interest.
+//        getQuicSession().setFillInterested(getStreamId(), false);
+
         boolean interested = isFillInterested();
         if (LOG.isDebugEnabled())
             LOG.debug("stream {} is readable, processing: {}", streamId, interested);
@@ -226,14 +239,20 @@ public class QuicStreamEndPoint extends AbstractEndPoint
     public void fillInterested(Callback callback)
     {
         super.fillInterested(callback);
-        getQuicSession().getProtocolSession().process();
+
+        // TODO: see above
+//        getQuicSession().setFillInterested(getStreamId(), true);
+
+        // Method produce() could block, but it's called synchronously from the producer thread
+        // which calls onReadable() above, so it will just go into re-producing and never block.
+        getQuicSession().getProtocolSession().produce();
     }
 
     @Override
     public boolean tryFillInterested(Callback callback)
     {
         boolean result = super.tryFillInterested(callback);
-        getQuicSession().getProtocolSession().process();
+        getQuicSession().getProtocolSession().produce();
         return result;
     }
 

jetty-quic/quic-quiche/pom.xml

@@ -19,20 +19,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-checkstyle-plugin</artifactId>
-        <configuration>
+        <version>${maven.checkstyle.plugin.version}</version>
-          <skip>true</skip>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-pmd-plugin</artifactId>
-        <configuration>
-          <skip>true</skip>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.codehaus.mojo</groupId>
-        <artifactId>findbugs-maven-plugin</artifactId>
         <configuration>
           <skip>true</skip>
         </configuration>

jetty-quic/quic-server/src/main/java/org/eclipse/jetty/quic/server/ServerProtocolSession.java

@@ -13,8 +13,11 @@
 
 package org.eclipse.jetty.quic.server;
 
+import java.util.function.Consumer;
+
 import org.eclipse.jetty.quic.common.ProtocolSession;
 import org.eclipse.jetty.quic.common.QuicStreamEndPoint;
+import org.eclipse.jetty.util.thread.Invocable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -22,6 +25,9 @@ public class ServerProtocolSession extends ProtocolSession
 {
     private static final Logger LOG = LoggerFactory.getLogger(ServerProtocolSession.class);
 
+    private final Runnable producer = Invocable.from(Invocable.InvocationType.BLOCKING, this::produce);
+    private final Consumer<QuicStreamEndPoint> configureProtocolEndPoint = this::configureProtocolEndPoint;
+
     public ServerProtocolSession(ServerQuicSession session)
     {
         super(session);
@@ -33,11 +39,17 @@ public class ServerProtocolSession extends ProtocolSession
         return (ServerQuicSession)super.getQuicSession();
     }
 
+    @Override
+    public Runnable getProducer()
+    {
+        return producer;
+    }
+
     @Override
     protected boolean onReadable(long readableStreamId)
     {
         // On the server, we need a get-or-create semantic in case of reads.
-        QuicStreamEndPoint streamEndPoint = getOrCreateStreamEndPoint(readableStreamId, this::configureProtocolEndPoint);
+        QuicStreamEndPoint streamEndPoint = getOrCreateStreamEndPoint(readableStreamId, configureProtocolEndPoint);
         if (LOG.isDebugEnabled())
             LOG.debug("stream #{} selected for read: {}", readableStreamId, streamEndPoint);
         return streamEndPoint.onReadable();

jetty-quic/quic-server/src/main/java/org/eclipse/jetty/quic/server/ServerQuicConnection.java

@@ -32,10 +32,7 @@ import org.eclipse.jetty.quic.server.internal.SimpleTokenValidator;
 import org.eclipse.jetty.server.Connector;
 import org.eclipse.jetty.util.BufferUtil;
 import org.eclipse.jetty.util.Callback;
-import org.eclipse.jetty.util.component.LifeCycle;
-import org.eclipse.jetty.util.thread.ExecutionStrategy;
 import org.eclipse.jetty.util.thread.Scheduler;
-import org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -48,7 +45,6 @@ public class ServerQuicConnection extends QuicConnection
 
     private final QuicheConfig quicheConfig;
     private final Connector connector;
-    private final AdaptiveExecutionStrategy strategy;
     private final SessionTimeouts sessionTimeouts;
 
     protected ServerQuicConnection(Connector connector, EndPoint endPoint, QuicheConfig quicheConfig)
@@ -56,7 +52,6 @@ public class ServerQuicConnection extends QuicConnection
         super(connector.getExecutor(), connector.getScheduler(), connector.getByteBufferPool(), endPoint);
         this.quicheConfig = quicheConfig;
         this.connector = connector;
-        this.strategy = new AdaptiveExecutionStrategy(new QuicProducer(), getExecutor());
         this.sessionTimeouts = new SessionTimeouts(connector.getScheduler());
     }
 
@@ -64,21 +59,13 @@ public class ServerQuicConnection extends QuicConnection
     public void onOpen()
     {
         super.onOpen();
-        LifeCycle.start(strategy);
         fillInterested();
     }
 
-    @Override
-    public void onClose(Throwable cause)
-    {
-        LifeCycle.stop(strategy);
-        super.onClose(cause);
-    }
-
     @Override
     public void onFillable()
     {
-        strategy.produce();
+        produce();
     }
 
     @Override
@@ -137,15 +124,6 @@ public class ServerQuicConnection extends QuicConnection
         // listening DatagramChannelEndPoint, so it must not be closed.
     }
 
-    private class QuicProducer implements ExecutionStrategy.Producer
-    {
-        @Override
-        public Runnable produce()
-        {
-            return receiveAndProcess();
-        }
-    }
-
     private class SessionTimeouts extends CyclicTimeouts<ServerQuicSession>
     {
         private SessionTimeouts(Scheduler scheduler)

jetty-util/src/main/java/org/eclipse/jetty/util/thread/Invocable.java

@@ -125,6 +125,35 @@ public interface Invocable
         return new ReadyTask(type, task);
     }
 
+    public static Runnable from(InvocationType type, Runnable task)
+    {
+        class RunnableInvocable implements Runnable, Invocable
+        {
+            private final InvocationType type;
+            private final Runnable task;
+
+            RunnableInvocable(InvocationType type, Runnable task)
+            {
+                this.type = type;
+                this.task = task;
+            }
+
+            @Override
+            public void run()
+            {
+                task.run();
+            }
+
+            @Override
+            public InvocationType getInvocationType()
+            {
+                return type;
+            }
+        }
+
+        return new RunnableInvocable(type, task);
+    }
+
     /**
      * Test if the current thread has been tagged as non blocking
      *