Thread safety and messaging bug fixes.

* Use the new AffinityExecutor code to fix some thread affinity issues where callbacks were running on the wrong threads. Add affinity assertions.
* Remove sleeps from UpdateBusinessDayProtocol.
* Remove a one-shot message handler before the callback is executed.
* Store un-routed messages in memory in ArtemisMessagingService to fix handler registration/message races. This is a temporary kludge until we use Artemis/MQ better.

src/main/kotlin/core/messaging/Messaging.kt

@@ -69,8 +69,8 @@ interface MessagingService {
  */
 fun MessagingService.runOnNextMessage(topic: String = "", executor: Executor? = null, callback: (Message) -> Unit) {
     addMessageHandler(topic, executor) { msg, reg ->
-        callback(msg)
         removeMessageHandler(reg)
+        callback(msg)
     }
 }
 

src/main/kotlin/core/messaging/StateMachineManager.kt

@@ -17,6 +17,7 @@ import core.serialization.THREAD_LOCAL_KRYO
 import core.serialization.createKryo
 import core.serialization.deserialize
 import core.serialization.serialize
+import core.utilities.AffinityExecutor
 import core.utilities.ProgressTracker
 import core.utilities.trace
 import org.slf4j.Logger
@@ -24,7 +25,6 @@ import org.slf4j.LoggerFactory
 import java.io.PrintWriter
 import java.io.StringWriter
 import java.util.*
-import java.util.concurrent.Executor
 import javax.annotation.concurrent.ThreadSafe
 
 /**
@@ -38,6 +38,9 @@ import javax.annotation.concurrent.ThreadSafe
  * A "state machine" is a class with a single call method. The call method and any others it invokes are rewritten by
  * a bytecode rewriting engine called Quasar, to ensure the code can be suspended and resumed at any point.
  *
+ * The SMM will always invoke the protocol fibers on the given [AffinityExecutor], regardless of which thread actually
+ * starts them via [add].
+ *
  * TODO: Session IDs should be set up and propagated automatically, on demand.
  * TODO: Consider the issue of continuation identity more deeply: is it a safe assumption that a serialised
  *       continuation is always unique?
@@ -50,7 +53,7 @@ import javax.annotation.concurrent.ThreadSafe
  * TODO: Implement stub/skel classes that provide a basic RPC framework on top of this.
  */
 @ThreadSafe
-class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor) {
+class StateMachineManager(val serviceHub: ServiceHub, val executor: AffinityExecutor) {
     // This map is backed by a database and will be used to store serialised state machines to disk, so we can resurrect
     // them across node restarts.
     private val checkpointsMap = serviceHub.storageService.stateMachines
@@ -114,7 +117,7 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
             val topic = checkpoint.awaitingTopic
 
             // And now re-wire the deserialised continuation back up to the network service.
-            serviceHub.networkService.runOnNextMessage(topic, runInThread) { netMsg ->
+            serviceHub.networkService.runOnNextMessage(topic, executor) { netMsg ->
                 // TODO: See security note below.
                 val obj: Any = THREAD_LOCAL_KRYO.get().readClassAndObject(Input(netMsg.data))
                 if (!awaitingObjectOfType.isInstance(obj))
@@ -154,15 +157,22 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
      * restarted with checkpointed state machines in the storage service.
      */
     fun <T> add(loggerName: String, logic: ProtocolLogic<T>): ListenableFuture<T> {
-        val logger = LoggerFactory.getLogger(loggerName)
+        try {
-        val fiber = ProtocolStateMachine(logic)
+            val logger = LoggerFactory.getLogger(loggerName)
-        // Need to add before iterating in case of immediate completion
+            val fiber = ProtocolStateMachine(logic)
-        _stateMachines.add(logic)
+            // Need to add before iterating in case of immediate completion
-        iterateStateMachine(fiber, serviceHub.networkService, logger, null, null) {
+            _stateMachines.add(logic)
-            it.start()
+            executor.executeASAP {
+                iterateStateMachine(fiber, serviceHub.networkService, logger, null, null) {
+                    it.start()
+                }
+                totalStartedProtocols.inc()
+            }
+            return fiber.resultFuture
+        } catch(e: Throwable) {
+            e.printStackTrace()
+            throw e
         }
-        totalStartedProtocols.inc()
-        return fiber.resultFuture
     }
 
     private fun persistCheckpoint(prevCheckpointKey: SecureHash?, new: ByteArray): SecureHash {
@@ -178,12 +188,12 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
 
     private fun iterateStateMachine(psm: ProtocolStateMachine<*>, net: MessagingService, logger: Logger,
                                     obj: Any?, prevCheckpointKey: SecureHash?, resumeFunc: (ProtocolStateMachine<*>) -> Unit) {
+        executor.checkOnThread()
         val onSuspend = fun(request: FiberRequest, serFiber: ByteArray) {
             // We have a request to do something: send, receive, or send-and-receive.
             if (request is FiberRequest.ExpectingResponse<*>) {
                 // Prepare a listener on the network that runs in the background thread when we received a message.
-                checkpointAndSetupMessageHandler(logger, net, psm, request.responseType,
+                checkpointAndSetupMessageHandler(logger, net, psm, request, prevCheckpointKey, serFiber)
-                        "${request.topic}.${request.sessionIDForReceive}", prevCheckpointKey, serFiber)
             }
             // If an object to send was provided (not null), send it now.
             request.obj?.let {
@@ -217,13 +227,22 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
     }
 
     private fun checkpointAndSetupMessageHandler(logger: Logger, net: MessagingService, psm: ProtocolStateMachine<*>,
-                                                 responseType: Class<*>, topic: String, prevCheckpointKey: SecureHash?,
+                                                 request: FiberRequest.ExpectingResponse<*>, prevCheckpointKey: SecureHash?,
                                                  serialisedFiber: ByteArray) {
-        val checkpoint = Checkpoint(serialisedFiber, logger.name, topic, responseType.name)
+        executor.checkOnThread()
+        val topic = "${request.topic}.${request.sessionIDForReceive}"
+        val checkpoint = Checkpoint(serialisedFiber, logger.name, topic, request.responseType.name)
         val curPersistedBytes = checkpoint.serialize().bits
         persistCheckpoint(prevCheckpointKey, curPersistedBytes)
         val newCheckpointKey = curPersistedBytes.sha256()
-        net.runOnNextMessage(topic, runInThread) { netMsg ->
+        logger.trace { "Waiting for message of type ${request.responseType.name} on $topic" }
+        var consumed = false
+        net.runOnNextMessage(topic, executor) { netMsg ->
+            // Some assertions to ensure we don't execute on the wrong thread or get executed more than once.
+            executor.checkOnThread()
+            check(netMsg.topic == topic) { "Topic mismatch: ${netMsg.topic} vs $topic" }
+            check(!consumed)
+            consumed = true
             // TODO: This is insecure: we should not deserialise whatever we find and *then* check.
             //
             // We should instead verify as we read the data that it's what we are expecting and throw as early as
@@ -232,9 +251,8 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
             // at the last moment when we do the downcast. However this would make protocol code harder to read and
             // make it more difficult to migrate to a more explicit serialisation scheme later.
             val obj: Any = THREAD_LOCAL_KRYO.get().readClassAndObject(Input(netMsg.data))
-            if (!responseType.isInstance(obj))
+            if (!request.responseType.isInstance(obj))
-                throw ClassCastException("Expected message of type ${responseType.name} but got ${obj.javaClass.name}")
+                throw IllegalStateException("Expected message of type ${request.responseType.name} but got ${obj.javaClass.name}", request.stackTraceInCaseOfProblems)
-            logger.trace { "<- $topic : message of type ${obj.javaClass.name}" }
             iterateStateMachine(psm, net, logger, obj, newCheckpointKey) {
                 try {
                     Fiber.unpark(it, QUASAR_UNBLOCKER)
@@ -245,11 +263,16 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
         }
     }
 
+    // TODO: Override more of this to avoid the case where Strand.sleep triggers a call to a scheduler that then runs on the wrong thread.
     object SameThreadFiberScheduler : FiberExecutorScheduler("Same thread scheduler", MoreExecutors.directExecutor())
 
     // TODO: Clean this up
     open class FiberRequest(val topic: String, val destination: MessageRecipients?,
                             val sessionIDForSend: Long, val sessionIDForReceive: Long, val obj: Any?) {
+        // This is used to identify where we suspended, in case of message mismatch errors and other things where we
+        // don't have the original stack trace because it's in a suspended fiber.
+        val stackTraceInCaseOfProblems = StackSnapshot()
+
         class ExpectingResponse<R : Any>(
                 topic: String,
                 destination: MessageRecipients?,
@@ -266,4 +289,7 @@ class StateMachineManager(val serviceHub: ServiceHub, val runInThread: Executor)
                 obj: Any?
         ) : FiberRequest(topic, destination, sessionIDForSend, -1, obj)
     }
+
 }
+
+class StackSnapshot : Throwable("This is a stack trace to help identify the source of the underlying problem")

src/main/kotlin/core/node/AbstractNode.kt

@@ -3,10 +3,7 @@ package core.node
 import api.APIServer
 import api.APIServerImpl
 import com.codahale.metrics.MetricRegistry
-import contracts.*
-import core.Contract
 import core.Party
-import core.crypto.SecureHash
 import core.crypto.generateKeyPair
 import core.messaging.MessagingService
 import core.messaging.StateMachineManager
@@ -14,6 +11,7 @@ import core.node.services.*
 import core.serialization.deserialize
 import core.serialization.serialize
 import core.testing.MockNetworkMapCache
+import core.utilities.AffinityExecutor
 import org.slf4j.Logger
 import java.nio.file.FileAlreadyExistsException
 import java.nio.file.Files
@@ -22,7 +20,6 @@ import java.security.KeyPair
 import java.security.PublicKey
 import java.time.Clock
 import java.util.*
-import java.util.concurrent.Executors
 
 /**
  * A base node implementation that can be customised either for production (with real implementations that do real
@@ -36,9 +33,9 @@ abstract class AbstractNode(val dir: Path, val configuration: NodeConfiguration,
 
     protected abstract val log: Logger
 
-    // We will run as much stuff in this thread as possible to keep the risk of thread safety bugs low during the
+    // We will run as much stuff in this single thread as possible to keep the risk of thread safety bugs low during the
     // low-performance prototyping period.
-    protected open val serverThread = Executors.newSingleThreadExecutor()
+    protected open val serverThread: AffinityExecutor = AffinityExecutor.ServiceAffinityExecutor("Node thread", 1)
 
     // Objects in this list will be scanned by the DataUploadServlet and can be handed new data via HTTP.
     // Don't mutate this after startup.

src/main/kotlin/core/node/Node.kt

@@ -58,9 +58,11 @@ class Node(dir: Path, val p2pAddr: HostAndPort, configuration: NodeConfiguration
     // when our process shuts down, but we try in stop() anyway just to be nice.
     private var nodeFileLock: FileLock? = null
 
-    override fun makeMessagingService(): MessagingService = ArtemisMessagingService(dir, p2pAddr)
+    override fun makeMessagingService(): MessagingService = ArtemisMessagingService(dir, p2pAddr, serverThread)
 
     private fun initWebServer(): Server {
+        // Note that the web server handlers will all run concurrently, and not on the node thread.
+
         val port = p2pAddr.port + 1   // TODO: Move this into the node config file.
         val server = Server(port)
 

src/main/kotlin/core/node/services/ArtemisMessagingService.kt

@@ -44,9 +44,14 @@ import javax.annotation.concurrent.ThreadSafe
  * The current implementation is skeletal and lacks features like security or firewall tunnelling (that is, you must
  * be able to receive TCP connections in order to receive messages). It is good enough for local communication within
  * a fully connected network, trusted network or on localhost.
+ *
+ * @param directory A place where Artemis can stash its message journal and other files.
+ * @param myHostPort What host and port to bind to for receiving inbound connections.
+ * @param defaultExecutor This will be used as the default executor to run message handlers on, if no other is specified.
  */
 @ThreadSafe
-class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort) : MessagingService {
+class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort,
+                              val defaultExecutor: Executor = RunOnCallerThread) : MessagingService {
     // In future: can contain onion routing info, etc.
     private data class Address(val hostAndPort: HostAndPort) : SingleMessageRecipient
 
@@ -83,6 +88,9 @@ class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort)
 
     private val handlers = CopyOnWriteArrayList<Handler>()
 
+    // TODO: This is not robust and needs to be replaced by more intelligently using the message queue server.
+    private val undeliveredMessages = CopyOnWriteArrayList<Message>()
+
     private fun getSendClient(addr: Address): ClientProducer {
         return mutex.locked {
             sendClients.getOrPut(addr) {
@@ -131,20 +139,10 @@ class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort)
             // This code runs for every inbound message.
             try {
                 if (!message.containsProperty(TOPIC_PROPERTY)) {
-                    log.warn("Received message without a ${TOPIC_PROPERTY} property, ignoring")
+                    log.warn("Received message without a $TOPIC_PROPERTY property, ignoring")
                     return@setMessageHandler
                 }
                 val topic = message.getStringProperty(TOPIC_PROPERTY)
-                // Because handlers is a COW list, the loop inside filter will operate on a snapshot. Handlers being added
-                // or removed whilst the filter is executing will not affect anything.
-                val deliverTo = handlers.filter { if (it.topic.isBlank()) true else it.topic == topic }
-
-                if (deliverTo.isEmpty()) {
-                    // This should probably be downgraded to a trace in future, so the protocol can evolve with new topics
-                    // without causing log spam.
-                    log.warn("Received message for $topic that doesn't have any registered handlers.")
-                    return@setMessageHandler
-                }
 
                 val bits = ByteArray(message.bodySize)
                 message.bodyBuffer.readBytes(bits)
@@ -156,15 +154,8 @@ class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort)
                     override val debugMessageID: String = message.messageID.toString()
                     override fun serialise(): ByteArray = bits
                 }
-                for (handler in deliverTo) {
+
-                    (handler.executor ?: RunOnCallerThread).execute {
+                deliverMessage(msg)
-                        try {
-                            handler.callback(msg, handler)
-                        } catch(e: Exception) {
-                            log.error("Caught exception whilst executing message handler for $topic", e)
-                        }
-                    }
-                }
             } finally {
                 message.acknowledge()
             }
@@ -174,6 +165,36 @@ class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort)
         mutex.locked { running = true }
     }
 
+    private fun deliverMessage(msg: Message): Boolean {
+        // Because handlers is a COW list, the loop inside filter will operate on a snapshot. Handlers being added
+        // or removed whilst the filter is executing will not affect anything.
+        val deliverTo = handlers.filter { if (it.topic.isBlank()) true else it.topic == msg.topic }
+
+        if (deliverTo.isEmpty()) {
+            // This should probably be downgraded to a trace in future, so the protocol can evolve with new topics
+            // without causing log spam.
+            log.warn("Received message for ${msg.topic} that doesn't have any registered handlers yet")
+
+            // This is a hack; transient messages held in memory isn't crash resistant.
+            // TODO: Use Artemis API more effectively so we don't pop messages off a queue that we aren't ready to use.
+            undeliveredMessages += msg
+
+            return false
+        }
+
+        for (handler in deliverTo) {
+            (handler.executor ?: defaultExecutor).execute {
+                try {
+                    handler.callback(msg, handler)
+                } catch(e: Exception) {
+                    log.error("Caught exception whilst executing message handler for ${msg.topic}", e)
+                }
+            }
+        }
+
+        return true
+    }
+
     override fun stop() {
         mutex.locked {
             for (producer in sendClients.values)
@@ -200,6 +221,7 @@ class ArtemisMessagingService(val directory: Path, val myHostPort: HostAndPort)
                                    callback: (Message, MessageHandlerRegistration) -> Unit): MessageHandlerRegistration {
         val handler = Handler(executor, topic, callback)
         handlers.add(handler)
+        undeliveredMessages.removeIf { deliverMessage(it) }
         return handler
     }
 

src/main/kotlin/core/testing/MockNode.kt

@@ -1,7 +1,6 @@
 package core.testing
 
 import com.google.common.jimfs.Jimfs
-import com.google.common.util.concurrent.MoreExecutors
 import core.Party
 import core.messaging.MessagingService
 import core.messaging.SingleMessageRecipient
@@ -12,14 +11,13 @@ import core.node.PhysicalLocation
 import core.testing.MockIdentityService
 import core.node.services.ServiceType
 import core.node.services.TimestamperService
+import core.utilities.AffinityExecutor
 import core.utilities.loggerFor
 import org.slf4j.Logger
 import java.nio.file.Files
 import java.nio.file.Path
 import java.time.Clock
 import java.util.*
-import java.util.concurrent.ExecutorService
-import java.util.concurrent.Executors
 
 /**
  * A mock node brings up a suite of in-memory services in a fast manner suitable for unit testing.
@@ -61,11 +59,11 @@ class MockNetwork(private val threadPerNode: Boolean = false,
     open class MockNode(dir: Path, config: NodeConfiguration, val mockNet: MockNetwork,
                         withTimestamper: NodeInfo?, val id: Int) : AbstractNode(dir, config, withTimestamper, Clock.systemUTC()) {
         override val log: Logger = loggerFor<MockNode>()
-        override val serverThread: ExecutorService =
+        override val serverThread: AffinityExecutor =
                 if (mockNet.threadPerNode)
-                    Executors.newSingleThreadExecutor()
+                    AffinityExecutor.ServiceAffinityExecutor("Mock node thread", 1)
                 else
-                    MoreExecutors.newDirectExecutorService()
+                    AffinityExecutor.SAME_THREAD
 
         // We only need to override the messaging service here, as currently everything that hits disk does so
         // through the java.nio API which we are already mocking via Jimfs.

src/main/kotlin/core/utilities/AffinityExecutor.kt

@@ -1,6 +1,5 @@
 package core.utilities
 
-import com.google.common.base.Preconditions.checkState
 import com.google.common.util.concurrent.Uninterruptibles
 import java.time.Duration
 import java.util.*
@@ -16,10 +15,18 @@ interface AffinityExecutor : Executor {
     val isOnThread: Boolean
 
     /** Throws an IllegalStateException if the current thread is equal to the thread this executor is backed by. */
-    fun checkOnThread()
+    fun checkOnThread() {
+        if (!isOnThread)
+            throw IllegalStateException("On wrong thread: " + Thread.currentThread())
+    }
 
     /** If isOnThread() then runnable is invoked immediately, otherwise the closure is queued onto the backing thread. */
-    fun executeASAP(runnable: () -> Unit)
+    fun executeASAP(runnable: () -> Unit) {
+        if (isOnThread)
+            runnable()
+        else
+            execute(runnable)
+    }
 
     /** Terminates any backing thread (pool) without waiting for tasks to finish. */
     fun shutdownNow()
@@ -35,43 +42,11 @@ interface AffinityExecutor : Executor {
             return CompletableFuture.supplyAsync(Supplier { fetcher() }, this).get()
     }
 
-    abstract class BaseAffinityExecutor protected constructor() : AffinityExecutor {
-        protected val exceptionHandler: Thread.UncaughtExceptionHandler
-
-        init {
-            exceptionHandler = Thread.currentThread().uncaughtExceptionHandler
-        }
-
-        abstract override val isOnThread: Boolean
-
-        override fun checkOnThread() {
-            checkState(isOnThread, "On wrong thread: %s", Thread.currentThread())
-        }
-
-        override fun executeASAP(runnable: () -> Unit) {
-            val command = {
-                try {
-                    runnable()
-                } catch (throwable: Throwable) {
-                    exceptionHandler.uncaughtException(Thread.currentThread(), throwable)
-                }
-            }
-            if (isOnThread)
-                command()
-            else {
-                execute(command)
-            }
-        }
-
-        // Must comply with the Executor definition w.r.t. exceptions here.
-        abstract override fun execute(command: Runnable)
-    }
-
     /**
      * An executor backed by thread pool (which may often have a single thread) which makes it easy to schedule
      * tasks in the future and verify code is running on the executor.
      */
-    class ServiceAffinityExecutor(threadName: String, numThreads: Int) : BaseAffinityExecutor() {
+    class ServiceAffinityExecutor(threadName: String, numThreads: Int) : AffinityExecutor {
         protected val threads = Collections.synchronizedSet(HashSet<Thread>())
 
         private val handler = Thread.currentThread().uncaughtExceptionHandler
@@ -81,8 +56,15 @@ interface AffinityExecutor : Executor {
             val threadFactory = fun(runnable: Runnable): Thread {
                 val thread = object : Thread() {
                     override fun run() {
-                        runnable.run()
+                        try {
-                        threads -= this
+                            runnable.run()
+                        } catch (e: Throwable) {
+                            e.printStackTrace()
+                            handler.uncaughtException(this, e)
+                            throw e
+                        } finally {
+                            threads -= this
+                        }
                     }
                 }
                 thread.isDaemon = true
@@ -100,29 +82,12 @@ interface AffinityExecutor : Executor {
 
         override fun execute(command: Runnable) {
             service.execute {
-                try {
+                command.run()
-                    command.run()
-                } catch (e: Throwable) {
-                    if (handler != null)
-                        handler.uncaughtException(Thread.currentThread(), e)
-                    else
-                        e.printStackTrace()
-                }
             }
         }
 
         fun <T> executeIn(time: Duration, command: () -> T): ScheduledFuture<T> {
-            return service.schedule(Callable {
+            return service.schedule(Callable { command() }, time.toMillis(), TimeUnit.MILLISECONDS)
-                try {
-                    command()
-                } catch (e: Throwable) {
-                    if (handler != null)
-                        handler.uncaughtException(Thread.currentThread(), e)
-                    else
-                        e.printStackTrace()
-                    throw e
-                }
-            }, time.toMillis(), TimeUnit.MILLISECONDS)
         }
 
         override fun shutdownNow() {
@@ -140,7 +105,7 @@ interface AffinityExecutor : Executor {
      *
      * @param alwaysQueue If true, executeASAP will never short-circuit and will always queue up.
      */
-    class Gate(private val alwaysQueue: Boolean = false) : BaseAffinityExecutor() {
+    class Gate(private val alwaysQueue: Boolean = false) : AffinityExecutor {
         private val thisThread = Thread.currentThread()
         private val commandQ = LinkedBlockingQueue<Runnable>()
 
@@ -163,7 +128,7 @@ interface AffinityExecutor : Executor {
     }
 
     companion object {
-        val SAME_THREAD: AffinityExecutor = object : BaseAffinityExecutor() {
+        val SAME_THREAD: AffinityExecutor = object : AffinityExecutor {
             override val isOnThread: Boolean get() = true
             override fun execute(command: Runnable) = command.run()
             override fun shutdownNow() {

src/main/kotlin/demos/protocols/UpdateBusinessDayProtocol.kt

@@ -1,7 +1,6 @@
 package demos.protocols
 
 import co.paralleluniverse.fibers.Suspendable
-import co.paralleluniverse.strands.Strand
 import contracts.DealState
 import contracts.InterestRateSwap
 import core.StateAndRef
@@ -100,7 +99,6 @@ object UpdateBusinessDayProtocol {
             progressTracker.currentStep = FIXING
 
             val participant = TwoPartyDealProtocol.Floater(party.address, sessionID, serviceHub.networkMapCache.timestampingNodes[0], dealStateAndRef, serviceHub.keyManagementService.freshKey(), sessionID, progressTracker.childrenFor[FIXING]!!)
-            Strand.sleep(100)
             val result = subProtocol(participant)
             return result.tx.outRef(0)
         }
@@ -119,7 +117,6 @@ object UpdateBusinessDayProtocol {
     data class UpdateBusinessDayMessage(val date: LocalDate, val sessionID: Long)
 
     object Handler {
-
         fun register(node: Node) {
             node.net.addMessageHandler("${TOPIC}.0") { msg, registration ->
                 // Just to validate we got the message

src/main/kotlin/protocols/TwoPartyDealProtocol.kt

@@ -79,7 +79,7 @@ object TwoPartyDealProtocol {
             val sessionID = random63BitValue()
 
             // Make the first message we'll send to kick off the protocol.
-            val hello = Handshake<U>(payload, myKeyPair.public, sessionID)
+            val hello = Handshake(payload, myKeyPair.public, sessionID)
 
             val maybeSTX = sendAndReceive<SignedTransaction>(DEAL_TOPIC, otherSide, otherSessionID, sessionID, hello)