Clarify exception handling in the SMM add method a bit.

node/src/main/kotlin/com/r3corda/node/services/persistence/DataVendingService.kt

@@ -99,21 +99,17 @@ object DataVending {
             // TODO: Do we want to be able to reject specific transactions on more complex rules, for example reject incoming
             //       cash without from unknown parties?
 
-            try {
+            services.startProtocol(NOTIFY_TX_PROTOCOL_TOPIC, ResolveTransactionsProtocol(req.tx, req.replyToParty))
-                services.startProtocol(NOTIFY_TX_PROTOCOL_TOPIC, ResolveTransactionsProtocol(req.tx, req.replyToParty))
+                .success {
-                    .success {
+                    services.recordTransactions(req.tx)
-                        services.recordTransactions(req.tx)
+                    val resp = NotifyTxResponseMessage(true)
-                        val resp = NotifyTxResponseMessage(true)
+                    val msg = net.createMessage(NOTIFY_TX_PROTOCOL_TOPIC, req.sessionID, resp.serialize().bits)
-                        val msg = net.createMessage(NOTIFY_TX_PROTOCOL_TOPIC, req.sessionID, resp.serialize().bits)
+                    net.send(msg, req.getReplyTo(services.networkMapCache))
-                        net.send(msg, req.getReplyTo(services.networkMapCache))
+                }.failure { throwable ->
-                    }.failure { throwable ->
+                    val resp = NotifyTxResponseMessage(false)
-                        val resp = NotifyTxResponseMessage(false)
+                    val msg = net.createMessage(NOTIFY_TX_PROTOCOL_TOPIC, req.sessionID, resp.serialize().bits)
-                        val msg = net.createMessage(NOTIFY_TX_PROTOCOL_TOPIC, req.sessionID, resp.serialize().bits)
+                    net.send(msg, req.getReplyTo(services.networkMapCache))
-                        net.send(msg, req.getReplyTo(services.networkMapCache))
+                }
-                    }
-            } catch(t: Exception) {
-                // Already handled by the hooks on the future, ignore
-            }
         }
 
         private fun handleTXRequest(req: FetchDataProtocol.Request): List<SignedTransaction?> {

node/src/main/kotlin/com/r3corda/node/services/statemachine/ProtocolStateMachineImpl.kt

@@ -12,6 +12,7 @@ import com.r3corda.core.utilities.UntrustworthyData
 import com.r3corda.node.services.api.ServiceHubInternal
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
+import java.util.concurrent.ExecutionException
 
 /**
  * A ProtocolStateMachine instance is a suspendable fiber that delegates all actual logic to a [ProtocolLogic] instance.
@@ -62,7 +63,7 @@ class ProtocolStateMachineImpl<R>(val logic: ProtocolLogic<R>,
         } catch (t: Throwable) {
             actionOnEnd()
             _resultFuture?.setException(t)
-            throw t
+            throw ExecutionException(t)
         }
 
         // This is to prevent actionOnEnd being called twice if it throws an exception

node/src/main/kotlin/com/r3corda/node/services/statemachine/StateMachineManager.kt

@@ -26,6 +26,7 @@ import java.io.PrintWriter
 import java.io.StringWriter
 import java.util.*
 import java.util.Collections.synchronizedMap
+import java.util.concurrent.ExecutionException
 import javax.annotation.concurrent.ThreadSafe
 
 /**
@@ -216,23 +217,32 @@ class StateMachineManager(val serviceHub: ServiceHubInternal, tokenizableService
      */
     fun <T> add(loggerName: String, logic: ProtocolLogic<T>): ListenableFuture<T> {
         val fiber = ProtocolStateMachineImpl(logic, scheduler, loggerName)
+        // Need to add before iterating in case of immediate completion
+        initFiber(fiber) {
+            val checkpoint = Checkpoint(serializeFiber(fiber), null)
+            checkpointStorage.addCheckpoint(checkpoint)
+            checkpoint
+        }
         try {
-            // Need to add before iterating in case of immediate completion
-            initFiber(fiber) {
-                val checkpoint = Checkpoint(serializeFiber(fiber), null)
-                checkpointStorage.addCheckpoint(checkpoint)
-                checkpoint
-            }
             executor.executeASAP {
                 iterateStateMachine(fiber, null) {
                     fiber.start()
                 }
                 totalStartedProtocols.inc()
             }
-        } catch (e: Throwable) {
+        } catch (e: ExecutionException) {
-            // TODO: We should be able to remove this as we get more confident that we never fail to log exceptions.
+            // There are two ways we can take exceptions in this method:
-            e.printStackTrace()
+            //
-            check(fiber.resultFuture.isDone)
+            // 1) A bug in the SMM code itself whilst setting up the new protocol. In that case the exception will
+            //    propagate out of this method as it would for any method.
+            //
+            // 2) An exception in the first part of the fiber after it's been invoked for the first time via
+            //    fiber.start(). In this case the exception will be caught and stashed in the protocol logic future,
+            //    then sent to the unhandled exception handler above which logs it, and is then rethrown wrapped
+            //    in an ExecutionException or RuntimeException+EE so we can just catch it here and ignore it.
+        } catch (e: RuntimeException) {
+            if (e.cause !is ExecutionException)
+                throw e
         }
         return fiber.resultFuture
     }