CORDA-3083: Backport dumpCheckpoints shell command (#5305)

This is a port of https://github.com/corda/corda/pull/5171 with some further improvements like printing out the contents of all the flows in the sub-flow stack (rather than just the current progress tracker step) and better error handling.

client/jackson/src/main/kotlin/net/corda/client/jackson/StringToMethodCallParser.kt

@@ -216,15 +216,17 @@ open class StringToMethodCallParser<in T : Any> @JvmOverloads constructor(
     /** Returns a string-to-string map of commands to a string describing available parameter types. */
     val availableCommands: Map<String, String>
         get() {
-            return methodMap.entries().map { entry ->
+            return methodMap.entries().mapNotNull { (name, args) ->
-                val (name, args) = entry   // TODO: Kotlin 1.1
+                if (args.parameterCount == 0) {
-                val argStr = if (args.parameterCount == 0) "" else {
+                    Pair(name, "")
-                    val paramNames = methodParamNames[name]!!
+                } else {
+                    methodParamNames[name]?. let { params ->
                         val typeNames = args.parameters.map { it.type.simpleName }
-                    val paramTypes = paramNames.zip(typeNames)
+                        val paramTypes = params.zip(typeNames)
-                    paramTypes.map { "${it.first}: ${it.second}" }.joinToString(", ")
+                        val paramNames = paramTypes.joinToString(", ") { "${it.first}: ${it.second}" }
+                        Pair(name, paramNames)
+                    }
                 }
-                Pair(name, argStr)
             }.toMap()
         }
 }

client/rpc/src/main/kotlin/net/corda/client/rpc/CordaRPCClient.kt

@@ -6,6 +6,7 @@ import net.corda.client.rpc.internal.RPCClientConfiguration
 import net.corda.core.context.Actor
 import net.corda.core.context.Trace
 import net.corda.core.messaging.CordaRPCOps
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.serialization.internal.effectiveSerializationEnv
 import net.corda.core.utilities.NetworkHostAndPort
 import net.corda.nodeapi.ArtemisTcpTransport.Companion.tcpTransport
@@ -104,7 +105,7 @@ class CordaRPCClient private constructor(
         }
     }
 
-    private val rpcClient = RPCClient<CordaRPCOps>(
+    private val rpcClient = RPCClient<InternalCordaRPCOps>(
             tcpTransport(ConnectionDirection.Outbound(), hostAndPort, config = sslConfiguration),
             configuration.toRpcClientConfiguration(),
             KRYO_RPC_CLIENT_CONTEXT
@@ -136,7 +137,7 @@ class CordaRPCClient private constructor(
      * @throws RPCException if the server version is too low or if the server isn't reachable within a reasonable timeout.
      */
     fun start(username: String, password: String, externalTrace: Trace?, impersonatedActor: Actor?): CordaRPCConnection {
-        return CordaRPCConnection(rpcClient.start(CordaRPCOps::class.java, username, password, externalTrace, impersonatedActor))
+        return CordaRPCConnection(rpcClient.start(InternalCordaRPCOps::class.java, username, password, externalTrace, impersonatedActor))
     }
 
     /**

core/src/main/kotlin/net/corda/core/internal/messaging/InternalCordaRPCOps.kt

@@ -0,0 +1,12 @@
+package net.corda.core.internal.messaging
+
+import net.corda.core.messaging.CordaRPCOps
+
+/**
+ * Contains internal RPC functions that should not be publicly exposed in [CordaRPCOps]
+ */
+interface InternalCordaRPCOps : CordaRPCOps {
+
+    /** Dump all the current flow checkpoints as JSON into a zip file in the node's log directory. */
+    fun dumpCheckpoints()
+}

core/src/test/kotlin/net/corda/core/flows/ContractUpgradeFlowTest.kt

@@ -20,6 +20,7 @@ import net.corda.finance.flows.CashIssueFlow
 import net.corda.node.internal.SecureCordaRPCOps
 import net.corda.node.internal.StartedNode
 import net.corda.node.services.Permissions.Companion.startFlow
+import net.corda.node.services.rpc.CheckpointDumper
 import net.corda.testing.contracts.DummyContract
 import net.corda.testing.contracts.DummyContractV2
 import net.corda.testing.contracts.DummyContractV3
@@ -128,7 +129,7 @@ class ContractUpgradeFlowTest {
         return startRpcClient<CordaRPCOps>(
                 rpcAddress = startRpcServer(
                         rpcUser = user,
-                        ops = SecureCordaRPCOps(node.services, node.smm, node.database, node.services)
+                        ops = SecureCordaRPCOps(node.services, node.smm, node.database, node.services, CheckpointDumper(node.checkpointStorage, node.database, node.services))
                 ).get().broker.hostAndPort!!,
                 username = user.username,
                 password = user.password

docs/source/changelog.rst

@@ -16,6 +16,10 @@ Version 3.4
 
 * Documentation updates
 
+* Information about checkpointed flows can be retrieved from the shell. Calling ``dumpCheckpoints`` will create a zip file inside the node's
+  ``log`` directory. This zip will contain a JSON representation of each checkpointed flow. This information can then be used to determine the
+  state of stuck flows or flows that experienced internal errors and were kept in the node for manual intervention.
+
 Version 3.3
 -----------
 

docs/source/upgrading-cordapps.rst

@@ -275,6 +275,17 @@ a drain is complete there should be no outstanding checkpoints or running flows.
 A node can be drained or undrained via RPC using the ``setFlowsDrainingModeEnabled`` method, and via the shell using
 the standard ``run`` command to invoke the RPC. See :doc:`shell` to learn more.
 
+To assist in draining a node, the ``dumpCheckpoints`` shell command will output JSON representations of each checkpointed flow.
+A zip containing the JSON files is created in the ``logs`` directory of the node. This information can then be used to determine the
+state of stuck flows or flows that experienced internal errors and were kept in the node for manual intervention. To drain these flows,
+the node will need to be restarted or the flow will need to be removed manually.
+
+.. warning:: Deleting checkpoints manually can lead to an inconsistent ledger among transacting parties. Great care
+             and coordination with a flow's counterparties must be taken to ensure that a initiating flow and flows responding to it are correctly
+             removed. This experience will be improved in the future. Making it easier to kill flows while notifying their counterparties.
+
+.. _contract_upgrading_ref:
+
 Contract and state versioning
 -----------------------------
 

node/src/main/java/net/corda/node/shell/RunShellCommand.java

@@ -1,9 +1,12 @@
 package net.corda.node.shell;
 
-import net.corda.core.messaging.*;
+import net.corda.client.jackson.StringToMethodCallParser;
-import net.corda.client.jackson.*;
+import net.corda.core.internal.messaging.InternalCordaRPCOps;
-import org.crsh.cli.*;
+import org.crsh.cli.Argument;
-import org.crsh.command.*;
+import org.crsh.cli.Command;
+import org.crsh.cli.Man;
+import org.crsh.cli.Usage;
+import org.crsh.command.InvocationContext;
 
 import java.util.*;
 
@@ -23,7 +26,7 @@ public class RunShellCommand extends InteractiveShellCommand {
             InvocationContext<Map> context,
             @Usage("The command to run") @Argument(unquote = false) List<String> command
     ) {
-        StringToMethodCallParser<CordaRPCOps> parser = new StringToMethodCallParser<>(CordaRPCOps.class, objectMapper());
+        StringToMethodCallParser<InternalCordaRPCOps> parser = new StringToMethodCallParser<>(InternalCordaRPCOps.class, objectMapper());
 
         if (command == null) {
             emitHelp(context, parser);
@@ -33,7 +36,7 @@ public class RunShellCommand extends InteractiveShellCommand {
         return InteractiveShell.runRPCFromString(command, out, context, ops());
     }
 
-    private void emitHelp(InvocationContext<Map> context, StringToMethodCallParser<CordaRPCOps> parser) {
+    private void emitHelp(InvocationContext<Map> context, StringToMethodCallParser<InternalCordaRPCOps> parser) {
         // Sends data down the pipeline about what commands are available. CRaSH will render it nicely.
         // Each element we emit is a map of column -> content.
         Set<Map.Entry<String, String>> entries = parser.getAvailableCommands().entrySet();

node/src/main/kotlin/net/corda/node/internal/AbstractNode.kt

@@ -17,6 +17,7 @@ import net.corda.core.internal.FlowStateMachine
 import net.corda.core.internal.VisibleForTesting
 import net.corda.core.internal.concurrent.map
 import net.corda.core.internal.concurrent.openFuture
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.internal.uncheckedCast
 import net.corda.core.messaging.*
 import net.corda.core.node.*
@@ -49,6 +50,7 @@ import net.corda.node.services.keys.PersistentKeyManagementService
 import net.corda.node.services.messaging.MessagingService
 import net.corda.node.services.network.*
 import net.corda.node.services.persistence.*
+import net.corda.node.services.rpc.CheckpointDumper
 import net.corda.node.services.schema.NodeSchemaService
 import net.corda.node.services.statemachine.*
 import net.corda.node.services.transactions.*
@@ -159,8 +161,8 @@ abstract class AbstractNode(val configuration: NodeConfiguration,
     private var _started: StartedNode<AbstractNode>? = null
 
     /** The implementation of the [CordaRPCOps] interface used by this node. */
-    open fun makeRPCOps(flowStarter: FlowStarter, database: CordaPersistence, smm: StateMachineManager): CordaRPCOps {
+    open fun makeRPCOps(flowStarter: FlowStarter, database: CordaPersistence, smm: StateMachineManager, checkpointDumper: CheckpointDumper): InternalCordaRPCOps {
-        return SecureCordaRPCOps(services, smm, database, flowStarter)
+        return SecureCordaRPCOps(services, smm, database, flowStarter, checkpointDumper)
     }
 
     private fun initCertificate() {
@@ -242,6 +244,8 @@ abstract class AbstractNode(val configuration: NodeConfiguration,
                     drainingModePollPeriod = configuration.drainingModePollPeriod,
                     nodeProperties = nodeProperties)
 
+            val checkpointDumper = CheckpointDumper(checkpointStorage, database, services)
+
             (serverThread as? ExecutorService)?.let {
                 runOnStop += {
                     // We wait here, even though any in-flight messages should have been drained away because the
@@ -252,7 +256,7 @@ abstract class AbstractNode(val configuration: NodeConfiguration,
             }
 
             makeVaultObservers(schedulerService, database.hibernateConfig, smm, schemaService, flowLogicRefFactory)
-            val rpcOps = makeRPCOps(flowStarter, database, smm)
+            val rpcOps = makeRPCOps(flowStarter, database, smm, checkpointDumper)
             startMessagingService(rpcOps)
             installCoreFlows()
             val cordaServices = installCordaServices(flowStarter)
@@ -260,6 +264,7 @@ abstract class AbstractNode(val configuration: NodeConfiguration,
             registerCordappFlows(smm)
             _services.rpcFlows += cordappLoader.cordapps.flatMap { it.rpcFlows }
             startShell(rpcOps)
+            checkpointDumper.start(tokenizableServices)
             Pair(StartedNodeImpl(this, _services, nodeInfo, checkpointStorage, smm, attachments, network, database, rpcOps, flowStarter, notaryService), schedulerService)
         }
 
@@ -293,7 +298,7 @@ abstract class AbstractNode(val configuration: NodeConfiguration,
      */
     protected abstract fun getRxIoScheduler(): Scheduler
 
-    open fun startShell(rpcOps: CordaRPCOps) {
+    open fun startShell(rpcOps: InternalCordaRPCOps) {
         InteractiveShell.startShell(configuration, rpcOps, securityManager, _services.identityService, _services.database)
     }
 

node/src/main/kotlin/net/corda/node/internal/CordaRPCOpsImpl.kt

@@ -15,6 +15,7 @@ import net.corda.core.identity.Party
 import net.corda.core.internal.FlowStateMachine
 import net.corda.core.internal.RPC_UPLOADER
 import net.corda.core.internal.STRUCTURAL_STEP_PREFIX
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.internal.sign
 import net.corda.core.messaging.*
 import net.corda.core.node.NodeInfo
@@ -28,6 +29,7 @@ import net.corda.core.utilities.contextLogger
 import net.corda.core.utilities.getOrThrow
 import net.corda.node.services.api.FlowStarter
 import net.corda.node.services.api.ServiceHubInternal
+import net.corda.node.services.rpc.CheckpointDumper
 import net.corda.node.services.messaging.context
 import net.corda.node.services.statemachine.StateMachineManager
 import net.corda.nodeapi.exceptions.RejectedCommandException
@@ -45,8 +47,9 @@ internal class CordaRPCOpsImpl(
         private val services: ServiceHubInternal,
         private val smm: StateMachineManager,
         private val database: CordaPersistence,
-        private val flowStarter: FlowStarter
+        private val flowStarter: FlowStarter,
-) : CordaRPCOps {
+        private val checkpointDumper: CheckpointDumper
+) : InternalCordaRPCOps {
     override fun networkMapSnapshot(): List<NodeInfo> {
         val (snapshot, updates) = networkMapFeed()
         updates.notUsed()
@@ -102,6 +105,8 @@ internal class CordaRPCOpsImpl(
         }
     }
 
+    override fun dumpCheckpoints() = checkpointDumper.dump()
+
     override fun stateMachinesSnapshot(): List<StateMachineInfo> {
         val (snapshot, updates) = stateMachinesFeed()
         updates.notUsed()

node/src/main/kotlin/net/corda/node/internal/RpcAuthorisationProxy.kt

@@ -7,7 +7,7 @@ import net.corda.core.flows.FlowLogic
 import net.corda.core.identity.AbstractParty
 import net.corda.core.identity.CordaX500Name
 import net.corda.core.identity.Party
-import net.corda.core.messaging.CordaRPCOps
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.messaging.DataFeed
 import net.corda.core.messaging.ParametersUpdateInfo
 import net.corda.core.node.NodeInfo
@@ -20,7 +20,7 @@ import java.io.InputStream
 import java.security.PublicKey
 
 // TODO change to KFunction reference after Kotlin fixes https://youtrack.jetbrains.com/issue/KT-12140
-class RpcAuthorisationProxy(private val implementation: CordaRPCOps, private val context: () -> RpcAuthContext) : CordaRPCOps {
+class RpcAuthorisationProxy(private val implementation: InternalCordaRPCOps, private val context: () -> RpcAuthContext) : InternalCordaRPCOps {
     override fun networkParametersFeed(): DataFeed<ParametersUpdateInfo?, ParametersUpdateInfo> = guard("networkParametersFeed") {
         implementation.networkParametersFeed()
     }
@@ -179,4 +179,6 @@ class RpcAuthorisationProxy(private val implementation: CordaRPCOps, private val
             return action()
         }
     }
+
+    override fun dumpCheckpoints() = guard("dumpCheckpoints", implementation::dumpCheckpoints)
 }

node/src/main/kotlin/net/corda/node/internal/SecureCordaRPCOps.kt

@@ -1,9 +1,11 @@
 package net.corda.node.internal
 
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.messaging.CordaRPCOps
 import net.corda.node.services.api.FlowStarter
 import net.corda.node.services.api.ServiceHubInternal
 import net.corda.node.services.messaging.rpcContext
+import net.corda.node.services.rpc.CheckpointDumper
 import net.corda.node.services.statemachine.StateMachineManager
 import net.corda.nodeapi.internal.persistence.CordaPersistence
 
@@ -14,7 +16,8 @@ class SecureCordaRPCOps(services: ServiceHubInternal,
                         smm: StateMachineManager,
                         database: CordaPersistence,
                         flowStarter: FlowStarter,
-                        val unsafe: CordaRPCOps = CordaRPCOpsImpl(services, smm, database, flowStarter)) : CordaRPCOps by RpcAuthorisationProxy(unsafe, ::rpcContext) {
+                        checkpointDumper: CheckpointDumper,
+                        val unsafe: InternalCordaRPCOps = CordaRPCOpsImpl(services, smm, database, flowStarter, checkpointDumper)) : InternalCordaRPCOps by RpcAuthorisationProxy(unsafe, ::rpcContext) {
 
     /**
      * Returns the RPC protocol version, which is the same the node's Platform Version. Exists since version 1 so guaranteed

node/src/main/kotlin/net/corda/node/services/api/CheckpointStorage.kt

@@ -3,6 +3,7 @@ package net.corda.node.services.api
 import net.corda.core.crypto.SecureHash
 import net.corda.core.serialization.SerializedBytes
 import net.corda.node.services.statemachine.FlowStateMachineImpl
+import java.util.stream.Stream
 
 /**
  * Thread-safe storage of fiber checkpoints.
@@ -27,6 +28,10 @@ interface CheckpointStorage {
      */
     fun forEach(block: (Checkpoint) -> Boolean)
 
+    /**
+     * Added as part of [CheckpointDumper] backport. Replacement for [CheckpointStorage.forEach].
+     */
+    fun getAllCheckpoints(): Stream<Pair<String, Checkpoint>>
 }
 
 // This class will be serialised, so everything it points to transitively must also be serialisable (with Kryo).

node/src/main/kotlin/net/corda/node/services/persistence/DBCheckpointStorage.kt

@@ -5,11 +5,12 @@ import net.corda.node.services.api.Checkpoint
 import net.corda.node.services.api.CheckpointStorage
 import net.corda.nodeapi.internal.persistence.NODE_DATABASE_PREFIX
 import net.corda.nodeapi.internal.persistence.currentDBSession
+import org.hibernate.annotations.Type
 import java.io.Serializable
+import java.util.stream.Stream
 import javax.persistence.Column
 import javax.persistence.Entity
 import javax.persistence.Id
-import org.hibernate.annotations.Type
 
 /**
  * Simple checkpoint key value storage in DB.
@@ -56,4 +57,14 @@ class DBCheckpointStorage : CheckpointStorage {
             }
         }
     }
+
+     override fun getAllCheckpoints(): Stream<Pair<String, Checkpoint>> {
+        val session = currentDBSession()
+        val criteriaQuery = session.criteriaBuilder.createQuery(DBCheckpoint::class.java)
+        val root = criteriaQuery.from(DBCheckpoint::class.java)
+        criteriaQuery.select(root)
+        return session.createQuery(criteriaQuery).stream().map {
+            it.checkpointId to Checkpoint(SerializedBytes(it.checkpoint))
+        }
+    }
 }

node/src/main/kotlin/net/corda/node/services/rpc/CheckpointDumper.kt

@@ -0,0 +1,420 @@
+package net.corda.node.services.rpc
+
+import co.paralleluniverse.fibers.Stack
+import com.fasterxml.jackson.annotation.*
+import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility
+import com.fasterxml.jackson.annotation.JsonInclude.Include
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.core.util.DefaultIndenter
+import com.fasterxml.jackson.core.util.DefaultPrettyPrinter
+import com.fasterxml.jackson.databind.*
+import com.fasterxml.jackson.databind.annotation.JsonSerialize
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.databind.ser.BeanPropertyWriter
+import com.fasterxml.jackson.databind.ser.BeanSerializerModifier
+import com.google.common.primitives.Booleans
+import net.corda.client.jackson.JacksonSupport
+import net.corda.client.jackson.internal.jsonObject
+import net.corda.core.context.InvocationOrigin
+import net.corda.core.contracts.*
+import net.corda.core.crypto.SecureHash
+import net.corda.core.crypto.TransactionSignature
+import net.corda.core.flows.FlowLogic
+import net.corda.core.flows.FlowSession
+import net.corda.core.identity.CordaX500Name
+import net.corda.core.identity.Party
+import net.corda.core.internal.div
+import net.corda.core.internal.exists
+import net.corda.core.internal.uncheckedCast
+import net.corda.core.serialization.SerializationDefaults
+import net.corda.core.serialization.SerializeAsToken
+import net.corda.core.serialization.SerializedBytes
+import net.corda.core.serialization.deserialize
+import net.corda.core.transactions.*
+import net.corda.core.utilities.ProgressTracker
+import net.corda.core.utilities.contextLogger
+import net.corda.node.internal.NodeStartup
+import net.corda.node.services.api.CheckpointStorage
+import net.corda.node.services.api.ServiceHubInternal
+import net.corda.node.services.statemachine.*
+import net.corda.nodeapi.internal.persistence.CordaPersistence
+import net.corda.nodeapi.internal.serialization.SerializeAsTokenContextImpl
+import net.corda.nodeapi.internal.serialization.withTokenContext
+import java.lang.reflect.Field
+import java.nio.file.Files
+import java.time.Duration
+import java.time.Instant
+import java.time.ZoneOffset.UTC
+import java.time.format.DateTimeFormatter
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicInteger
+import java.util.zip.ZipEntry
+import java.util.zip.ZipOutputStream
+
+class CheckpointDumper(private val checkpointStorage: CheckpointStorage, private val database: CordaPersistence, private val serviceHub: ServiceHubInternal) {
+    companion object {
+        private val TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyyMMdd-HHmmss").withZone(UTC)
+        private val log = contextLogger()
+    }
+
+    private val lock = AtomicInteger(0)
+
+    private lateinit var checkpointSerializationContext: SerializeAsTokenContextImpl
+    private lateinit var writer: ObjectWriter
+
+    fun start(tokenizableServices: List<Any>) {
+        checkpointSerializationContext = SerializeAsTokenContextImpl(
+                tokenizableServices,
+                SerializationDefaults.SERIALIZATION_FACTORY,
+                SerializationDefaults.CHECKPOINT_CONTEXT,
+                serviceHub
+        )
+
+        val mapper = JacksonSupport.createNonRpcMapper()
+        mapper.registerModule(SimpleModule().apply {
+            setSerializerModifier(CheckpointDumperBeanModifier)
+            addSerializer(FlowSessionImplSerializer)
+            addSerializer(MapSerializer)
+            addSerializer(AttachmentSerializer)
+            setMixInAnnotation(FlowLogic::class.java, FlowLogicMixin::class.java)
+            setMixInAnnotation(SessionId::class.java, SessionIdMixin::class.java)
+            setMixInAnnotation(SignedTransaction::class.java, SignedTransactionMixin::class.java)
+            setMixInAnnotation(WireTransaction::class.java, WireTransactionMixin::class.java)
+            setMixInAnnotation(FlowSessionInternal::class.java, FlowSessionInternalMixin::class.java)
+        })
+        val prettyPrinter = DefaultPrettyPrinter().apply {
+            indentArraysWith(DefaultIndenter.SYSTEM_LINEFEED_INSTANCE)
+        }
+        writer = mapper.writer(prettyPrinter)
+    }
+
+    fun dump() {
+        val now = serviceHub.clock.instant()
+        val file = serviceHub.configuration.baseDirectory / NodeStartup.LOGS_DIRECTORY_NAME / "checkpoints_dump-${TIME_FORMATTER.format(now)}.zip"
+        try {
+            if (lock.getAndIncrement() == 0 && !file.exists()) {
+                database.transaction {
+                    checkpointStorage.getAllCheckpoints().use { stream ->
+                        ZipOutputStream(Files.newOutputStream(file)).use { zip ->
+                            stream.forEach { (runId, serialisedCheckpoint) ->
+                                try {
+                                    val checkpoint = serialisedCheckpoint.serializedFiber.deserialize(
+                                            context = SerializationDefaults.CHECKPOINT_CONTEXT.withTokenContext(checkpointSerializationContext)
+                                    )
+                                    val json = checkpoint.toJson(runId, now)
+                                    val jsonBytes = writer.writeValueAsBytes(json)
+                                    zip.putNextEntry(ZipEntry("${json.topLevelFlowClass.simpleName}-$runId.json"))
+                                    zip.write(jsonBytes)
+                                    zip.closeEntry()
+                                } catch (e: Exception) {
+                                    log.info("Failed to deserialise checkpoint with id: $runId", e)
+                                    zip.putNextEntry(ZipEntry("Undeserialisable-checkpoint-$runId.json"))
+                                    zip.write(
+                                            """
+                                            *** Unable to deserialise checkpoint: ${e.message} ***
+                                            *** Check logs for further information, checkpoint id: $runId ***
+                                            """
+                                                    .trimIndent().toByteArray()
+                                    )
+                                    zip.closeEntry()
+                                }
+                            }
+                        }
+                    }
+                }
+            } else {
+                log.info("Flow dump already in progress, skipping current call")
+            }
+        } finally {
+            lock.decrementAndGet()
+        }
+    }
+
+    private fun FlowStateMachineImpl<*>.toJson(id: String, now: Instant): CheckpointJson {
+        // Poke into Quasar's stack and find the object references to the sub-flows so that we can correctly get the current progress
+        // step for each sub-call.
+        val stackObjects = declaredField<Stack>("stack").value
+                .declaredField<Array<*>>("dataObject").value
+                .filterIsInstance<FlowLogic<*>>()
+                .toSet()
+                .map {
+                    FlowCall(
+                            it.javaClass,
+                            if (it.progressTracker?.currentStep == ProgressTracker.UNSTARTED) null else it.progressTracker?.currentStep?.label,
+                            it
+                    )
+                }
+
+        val activeSessions = openSessions.mapNotNull { (key, session) ->
+            ActiveSession(
+                    key.second,
+                    session.ourSessionId,
+                    session.receivedMessages.toList(),
+                    (session.state as? FlowSessionState.Initiated)?.peerSessionId
+            )
+        }
+
+        return CheckpointJson(
+                id,
+                logic.javaClass,
+                stackObjects,
+                waitingForResponse?.toSuspendedOn(suspendedTimestamp(), now),
+                context.origin.toOrigin(),
+                ourIdentity,
+                activeSessions
+        )
+    }
+
+    private fun FlowStateMachineImpl<*>.suspendedTimestamp(): Instant = context.trace.invocationId.timestamp
+
+    @Suppress("unused")
+    private class FlowCall(val flowClass: Class<*>, val progressStep: String?, val flowLogic: FlowLogic<*>)
+
+    @Suppress("unused")
+    @JsonInclude(Include.NON_NULL)
+    private class Origin(
+            val rpc: String? = null,
+            val peer: CordaX500Name? = null,
+            val service: String? = null,
+            val scheduled: ScheduledStateRef? = null,
+            val shell: InvocationOrigin.Shell? = null
+    )
+
+    private fun InvocationOrigin.toOrigin(): Origin {
+        return when (this) {
+            is InvocationOrigin.RPC -> Origin(rpc = actor.id.value)
+            is InvocationOrigin.Peer -> Origin(peer = party)
+            is InvocationOrigin.Service -> Origin(service = serviceClassName)
+            is InvocationOrigin.Scheduled -> Origin(scheduled = scheduledState)
+            is InvocationOrigin.Shell -> Origin(shell = this)
+        }
+    }
+
+    @Suppress("unused")
+    private class CheckpointJson(
+            val flowId: String,
+            val topLevelFlowClass: Class<FlowLogic<*>>,
+            val flowCallStack: List<FlowCall>,
+            val suspendedOn: SuspendedOn?,
+            val origin: Origin,
+            val ourIdentity: Party,
+            val activeSessions: List<ActiveSession>
+    )
+
+    @Suppress("unused")
+    @JsonInclude(Include.NON_NULL)
+    private class SuspendedOn(
+            val receive: ReceiveOnly? = null,
+            val sendAndReceive: SendAndReceiveJson? = null,
+            val waitForLedgerCommit: SecureHash? = null,
+            val receiveAll: ReceiveAll? = null
+    ) {
+        @JsonFormat(pattern = "yyyy-MM-dd'T'HH:mm:ss", timezone = "UTC")
+        lateinit var suspendedTimestamp: Instant
+        var secondsSpentWaiting: Long = 0
+    }
+
+    @Suppress("unused")
+    private class SendAndReceiveJson(val session: FlowSession, val sentPayloadType: Class<*>?, val sentPayload: Any?, val receivedPayloadType: Class<*>?)
+
+    private fun WaitingRequest.toSuspendedOn(suspendedTimestamp: Instant, now: Instant): SuspendedOn {
+        fun SendAndReceive.toJson(): SendAndReceiveJson {
+            val payload = when (this.message) {
+                is ExistingSessionMessage -> (message.payload as? DataSessionMessage)?.payload?.deserializeOrOutputPlaceholder()
+                is InitialSessionMessage -> message.firstPayload?.deserializeOrOutputPlaceholder()
+            }
+            return SendAndReceiveJson(session.flowSession, payload?.javaClass, payload, userReceiveType)
+        }
+        return when (this) {
+            is ReceiveOnly -> SuspendedOn(receive = this)
+            is SendAndReceive -> SuspendedOn(sendAndReceive = this.toJson())
+            is WaitForLedgerCommit -> SuspendedOn(waitForLedgerCommit = hash)
+            is ReceiveAll -> SuspendedOn(receiveAll = this)
+            // should not be possible but the compiler wont let it through without this case
+            else -> SuspendedOn()
+
+        }.also {
+            it.suspendedTimestamp = suspendedTimestamp
+            it.secondsSpentWaiting = TimeUnit.MILLISECONDS.toSeconds(Duration.between(suspendedTimestamp, now).toMillis())
+        }
+    }
+
+    private fun SerializedBytes<Any>.deserializeOrOutputPlaceholder() = try {
+        deserialize()
+    } catch (e: Exception) {
+        "*** Unable to deserialise message payload: ${e.message} ***"
+    }
+
+    @Suppress("unused")
+    private class ActiveSession(
+            val peer: Party,
+            val ourSessionId: SessionId,
+            val receivedMessages: List<ReceivedSessionMessage>,
+            val peerSessionId: SessionId?
+    )
+
+    @Suppress("unused")
+    private interface SessionIdMixin {
+        @get:JsonValue
+        val toLong: Long
+    }
+
+    @JsonAutoDetect(getterVisibility = Visibility.NONE, isGetterVisibility = Visibility.NONE, fieldVisibility = Visibility.ANY)
+    @JsonIgnoreProperties("flowUsedForSessions")
+    private interface FlowLogicMixin
+
+    private object CheckpointDumperBeanModifier : BeanSerializerModifier() {
+        override fun changeProperties(config: SerializationConfig,
+                                      beanDesc: BeanDescription,
+                                      beanProperties: MutableList<BeanPropertyWriter>): MutableList<BeanPropertyWriter> {
+            // Remove references to any node singletons
+            beanProperties.removeIf { it.type.isTypeOrSubTypeOf(SerializeAsToken::class.java) }
+            if (FlowLogic::class.java.isAssignableFrom(beanDesc.beanClass)) {
+                beanProperties.removeIf {
+                    it.type.isTypeOrSubTypeOf(ProgressTracker::class.java) || it.name == "_stateMachine" || it.name == "deprecatedPartySessionMap"
+                }
+            }
+            return beanProperties
+        }
+    }
+
+    private object FlowSessionImplSerializer : JsonSerializer<FlowSessionImpl>() {
+        override fun serialize(value: FlowSessionImpl, gen: JsonGenerator, serializers: SerializerProvider) {
+            gen.jsonObject {
+                writeObjectField("peer", value.counterparty)
+            }
+        }
+
+        override fun handledType(): Class<FlowSessionImpl> = FlowSessionImpl::class.java
+    }
+
+    private object AttachmentSerializer : JsonSerializer<Attachment>() {
+        override fun serialize(value: Attachment, gen: JsonGenerator, serializers: SerializerProvider) = gen.writeObject(value.id)
+        override fun handledType(): Class<Attachment> = Attachment::class.java
+    }
+
+    private object MapSerializer : JsonSerializer<Map<Any, Any>>() {
+        override fun serialize(map: Map<Any, Any>, gen: JsonGenerator, serializers: SerializerProvider) {
+            gen.writeStartArray(map.size)
+            map.forEach { key, value ->
+                gen.jsonObject {
+                    writeObjectField("key", key)
+                    writeObjectField("value", value)
+                }
+            }
+            gen.writeEndArray()
+        }
+
+        override fun handledType(): Class<Map<Any, Any>> = uncheckedCast(Map::class.java)
+    }
+
+    @JsonSerialize(using = SignedTransactionSerializer::class)
+    private interface SignedTransactionMixin
+
+    private class SignedTransactionSerializer : JsonSerializer<SignedTransaction>() {
+        override fun serialize(value: SignedTransaction, gen: JsonGenerator, serializers: SerializerProvider) {
+            val core = value.coreTransaction
+            val stxJson = when (core) {
+                is WireTransaction -> StxJson(wire = core, signatures = value.sigs)
+                is FilteredTransaction -> StxJson(filtered = core, signatures = value.sigs)
+                is NotaryChangeWireTransaction -> StxJson(notaryChangeWire = core, signatures = value.sigs)
+                is ContractUpgradeWireTransaction -> StxJson(contractUpgradeWire = core, signatures = value.sigs)
+                is ContractUpgradeFilteredTransaction -> StxJson(contractUpgradeFiltered = core, signatures = value.sigs)
+                else -> throw IllegalArgumentException("Don't know about ${core.javaClass}")
+            }
+            gen.writeObject(stxJson)
+        }
+    }
+
+    @JsonInclude(Include.NON_NULL)
+    private data class StxJson(
+            val wire: WireTransaction? = null,
+            val filtered: FilteredTransaction? = null,
+            val notaryChangeWire: NotaryChangeWireTransaction? = null,
+            val contractUpgradeWire: ContractUpgradeWireTransaction? = null,
+            val contractUpgradeFiltered: ContractUpgradeFilteredTransaction? = null,
+            val signatures: List<TransactionSignature>
+    ) {
+        init {
+            val count = Booleans.countTrue(wire != null, filtered != null, notaryChangeWire != null, contractUpgradeWire != null, contractUpgradeFiltered != null)
+            require(count == 1) { this }
+        }
+    }
+
+    @JsonSerialize(using = WireTransactionSerializer::class)
+    private interface WireTransactionMixin
+
+    private class WireTransactionSerializer : JsonSerializer<WireTransaction>() {
+        override fun serialize(value: WireTransaction, gen: JsonGenerator, serializers: SerializerProvider) {
+            gen.writeObject(WireTransactionJson(
+                    value.id,
+                    value.notary,
+                    value.inputs,
+                    value.outputs,
+                    value.commands,
+                    value.timeWindow,
+                    value.attachments,
+                    value.privacySalt
+            ))
+        }
+    }
+
+    private class WireTransactionJson(
+            val id: SecureHash,
+            val notary: Party?,
+            val inputs: List<StateRef>,
+            val outputs: List<TransactionState<*>>,
+            val commands: List<Command<*>>,
+            val timeWindow: TimeWindow?,
+            val attachments: List<SecureHash>,
+            val privacySalt: PrivacySalt
+    )
+
+    @JsonIgnoreProperties("flow", "fiber")
+    @JsonAutoDetect(getterVisibility = Visibility.NONE, isGetterVisibility = Visibility.NONE, fieldVisibility = Visibility.ANY)
+    private interface FlowSessionInternalMixin
+}
+
+// Taken from newer corda version due to parent classes not being searched for fields
+// needed to access `stack` inside `FlowStateMachineImpl`
+private fun <T> Any.declaredField(name: String): DeclaredField<T> = DeclaredField(javaClass, name, this)
+
+private class DeclaredField<T>(clazz: Class<*>, name: String, private val receiver: Any?) {
+    private val javaField = findField(name, clazz)
+    var value: T
+        get() {
+            synchronized(this) {
+                return javaField.accessible { uncheckedCast<Any?, T>(get(receiver)) }
+            }
+        }
+        set(value) {
+            synchronized(this) {
+                javaField.accessible {
+                    set(receiver, value)
+                }
+            }
+        }
+    val name: String = javaField.name
+
+    private fun <RESULT> Field.accessible(action: Field.() -> RESULT): RESULT {
+        val accessible = isAccessible
+        isAccessible = true
+        try {
+            return action(this)
+        } finally {
+            isAccessible = accessible
+        }
+    }
+
+    @Throws(NoSuchFieldException::class)
+    private fun findField(fieldName: String, clazz: Class<*>?): Field {
+        if (clazz == null) {
+            throw NoSuchFieldException(fieldName)
+        }
+        return try {
+            return clazz.getDeclaredField(fieldName)
+        } catch (e: NoSuchFieldException) {
+            findField(fieldName, clazz.superclass)
+        }
+    }
+}

node/src/main/kotlin/net/corda/node/shell/CordaAuthenticationPlugin.kt

@@ -3,7 +3,7 @@ package net.corda.node.shell
 import net.corda.core.context.Actor
 import net.corda.core.context.InvocationContext
 import net.corda.core.identity.CordaX500Name
-import net.corda.core.messaging.CordaRPCOps
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.node.internal.security.Password
 import net.corda.node.internal.security.RPCSecurityManager
 import net.corda.node.internal.security.tryAuthenticate
@@ -11,7 +11,7 @@ import org.crsh.auth.AuthInfo
 import org.crsh.auth.AuthenticationPlugin
 import org.crsh.plugin.CRaSHPlugin
 
-class CordaAuthenticationPlugin(private val rpcOps: CordaRPCOps, private val securityManager: RPCSecurityManager, private val nodeLegalName: CordaX500Name) : CRaSHPlugin<AuthenticationPlugin<String>>(), AuthenticationPlugin<String> {
+class CordaAuthenticationPlugin(private val rpcOps: InternalCordaRPCOps, private val securityManager: RPCSecurityManager, private val nodeLegalName: CordaX500Name) : CRaSHPlugin<AuthenticationPlugin<String>>(), AuthenticationPlugin<String> {
 
     override fun getImplementation(): AuthenticationPlugin<String> = this
 

node/src/main/kotlin/net/corda/node/shell/CordaSSHAuthInfo.kt

@@ -1,9 +1,9 @@
 package net.corda.node.shell
 
-import net.corda.core.messaging.CordaRPCOps
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.node.utilities.ANSIProgressRenderer
 import org.crsh.auth.AuthInfo
 
-class CordaSSHAuthInfo(val successful: Boolean, val rpcOps: CordaRPCOps, val ansiProgressRenderer: ANSIProgressRenderer? = null) : AuthInfo {
+class CordaSSHAuthInfo(val successful: Boolean, val rpcOps: InternalCordaRPCOps, val ansiProgressRenderer: ANSIProgressRenderer? = null) : AuthInfo {
     override fun isSuccessful(): Boolean = successful
 }

node/src/main/kotlin/net/corda/node/shell/InteractiveShell.kt

@@ -18,6 +18,7 @@ import net.corda.core.internal.*
 import net.corda.core.internal.concurrent.doneFuture
 import net.corda.core.internal.concurrent.openFuture
 import net.corda.core.messaging.CordaRPCOps
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.messaging.DataFeed
 import net.corda.core.messaging.FlowProgressHandle
 import net.corda.core.messaging.StateMachineUpdate
@@ -81,7 +82,7 @@ object InteractiveShell {
     private lateinit var node: StartedNode<Node>
     @VisibleForTesting
     internal lateinit var database: CordaPersistence
-    private lateinit var rpcOps: CordaRPCOps
+    private lateinit var rpcOps: InternalCordaRPCOps
     private lateinit var securityManager: RPCSecurityManager
     private lateinit var identityService: IdentityService
     private var shell: Shell? = null
@@ -91,7 +92,7 @@ object InteractiveShell {
      * Starts an interactive shell connected to the local terminal. This shell gives administrator access to the node
      * internals.
      */
-    fun startShell(configuration: NodeConfiguration, cordaRPCOps: CordaRPCOps, securityManager: RPCSecurityManager, identityService: IdentityService, database: CordaPersistence) {
+    fun startShell(configuration: NodeConfiguration, cordaRPCOps: InternalCordaRPCOps, securityManager: RPCSecurityManager, identityService: IdentityService, database: CordaPersistence) {
         this.rpcOps = cordaRPCOps
         this.securityManager = securityManager
         this.identityService = identityService
@@ -368,8 +369,8 @@ object InteractiveShell {
     }
 
     @JvmStatic
-    fun runRPCFromString(input: List<String>, out: RenderPrintWriter, context: InvocationContext<out Any>, cordaRPCOps: CordaRPCOps): Any? {
+    fun runRPCFromString(input: List<String>, out: RenderPrintWriter, context: InvocationContext<out Any>, cordaRPCOps: InternalCordaRPCOps): Any? {
-        val parser = StringToMethodCallParser(CordaRPCOps::class.java, context.attributes["mapper"] as ObjectMapper)
+        val parser = StringToMethodCallParser(InternalCordaRPCOps::class.java, context.attributes["mapper"] as ObjectMapper)
 
         val cmd = input.joinToString(" ").trim { it <= ' ' }
         if (cmd.toLowerCase().startsWith("startflow")) {

node/src/main/kotlin/net/corda/node/shell/RPCOpsWithContext.kt

@@ -1,7 +1,7 @@
 package net.corda.node.shell
 
 import net.corda.core.context.InvocationContext
-import net.corda.core.messaging.CordaRPCOps
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.utilities.getOrThrow
 import net.corda.node.internal.security.AuthorizingSubject
 import net.corda.node.services.messaging.CURRENT_RPC_CONTEXT
@@ -11,9 +11,9 @@ import java.lang.reflect.Proxy
 import java.util.concurrent.CompletableFuture
 import java.util.concurrent.Future
 
-fun makeRPCOpsWithContext(cordaRPCOps: CordaRPCOps, invocationContext:InvocationContext, authorizingSubject: AuthorizingSubject) : CordaRPCOps {
+fun makeRPCOpsWithContext(cordaRPCOps: InternalCordaRPCOps, invocationContext:InvocationContext, authorizingSubject: AuthorizingSubject) : InternalCordaRPCOps {
 
-    return Proxy.newProxyInstance(CordaRPCOps::class.java.classLoader, arrayOf(CordaRPCOps::class.java), { _, method, args ->
+    return Proxy.newProxyInstance(InternalCordaRPCOps::class.java.classLoader, arrayOf(InternalCordaRPCOps::class.java), { _, method, args ->
         RPCContextRunner(invocationContext, authorizingSubject) {
             try {
                 method.invoke(cordaRPCOps, *(args ?: arrayOf()))
@@ -22,7 +22,7 @@ fun makeRPCOpsWithContext(cordaRPCOps: CordaRPCOps, invocationContext:Invocation
                 throw e.targetException
             }
         }.get().getOrThrow()
-    }) as CordaRPCOps
+    }) as InternalCordaRPCOps
 }
 
 private class RPCContextRunner<T>(val invocationContext: InvocationContext, val authorizingSubject: AuthorizingSubject, val block:() -> T): Thread() {

node/src/test/kotlin/net/corda/node/CordaRPCOpsImplTest.kt

@@ -32,6 +32,7 @@ import net.corda.node.services.Permissions.Companion.invokeRpc
 import net.corda.node.services.Permissions.Companion.startFlow
 import net.corda.node.services.messaging.CURRENT_RPC_CONTEXT
 import net.corda.node.services.messaging.RpcAuthContext
+import net.corda.node.services.rpc.CheckpointDumper
 import net.corda.nodeapi.internal.config.User
 import net.corda.testing.core.ALICE_NAME
 import net.corda.testing.core.expect
@@ -82,7 +83,7 @@ class CordaRPCOpsImplTest {
     fun setup() {
         mockNet = InternalMockNetwork(cordappPackages = listOf("net.corda.finance.contracts.asset", "net.corda.finance.schemas"))
         aliceNode = mockNet.createNode(InternalMockNodeParameters(legalName = ALICE_NAME))
-        rpc = SecureCordaRPCOps(aliceNode.services, aliceNode.smm, aliceNode.database, aliceNode.services)
+        rpc = SecureCordaRPCOps(aliceNode.services, aliceNode.smm, aliceNode.database, aliceNode.services, CheckpointDumper(aliceNode.checkpointStorage, aliceNode.database, aliceNode.services))
         CURRENT_RPC_CONTEXT.set(RpcAuthContext(InvocationContext.rpc(testActor()), buildSubject("TEST_USER", emptySet())))
 
         mockNet.runNetwork()

testing/node-driver/src/main/kotlin/net/corda/testing/node/internal/InternalMockNetwork.kt

@@ -13,8 +13,8 @@ import net.corda.core.identity.PartyAndCertificate
 import net.corda.core.internal.VisibleForTesting
 import net.corda.core.internal.createDirectories
 import net.corda.core.internal.createDirectory
+import net.corda.core.internal.messaging.InternalCordaRPCOps
 import net.corda.core.internal.uncheckedCast
-import net.corda.core.messaging.CordaRPCOps
 import net.corda.core.messaging.MessageRecipients
 import net.corda.core.messaging.RPCOps
 import net.corda.core.messaging.SingleMessageRecipient
@@ -278,7 +278,7 @@ open class InternalMockNetwork(private val cordappPackages: List<String>,
             return E2ETestKeyManagementService(identityService, keyPairs)
         }
 
-        override fun startShell(rpcOps: CordaRPCOps) {
+        override fun startShell(rpcOps: InternalCordaRPCOps) {
             //No mock shell
         }