RPC changes (#3697)

* Eliminate un-necessary reference to Kryo in the comment

* RPC documentation update.

* Rename RpcClientObservableSerializer into RpcClientObservableDeSerializer

client/rpc/src/main/kotlin/net/corda/client/rpc/internal/RPCClientProxyHandler.kt

@@ -10,7 +10,7 @@ import com.google.common.util.concurrent.ThreadFactoryBuilder
 import net.corda.client.rpc.CordaRPCClientConfiguration
 import net.corda.client.rpc.RPCException
 import net.corda.client.rpc.RPCSinceVersion
-import net.corda.client.rpc.internal.serialization.amqp.RpcClientObservableSerializer
+import net.corda.client.rpc.internal.serialization.amqp.RpcClientObservableDeSerializer
 import net.corda.core.context.Actor
 import net.corda.core.context.Trace
 import net.corda.core.context.Trace.InvocationId
@@ -155,7 +155,7 @@ class RPCClientProxyHandler(
     private val observablesToReap = ThreadBox(object {
         var observables = ArrayList<InvocationId>()
     })
-    private val serializationContextWithObservableContext = RpcClientObservableSerializer.createContext(serializationContext, observableContext)
+    private val serializationContextWithObservableContext = RpcClientObservableDeSerializer.createContext(serializationContext, observableContext)
 
     private fun createRpcObservableMap(): RpcObservableMap {
         val onObservableRemove = RemovalListener<InvocationId, UnicastSubject<Notification<*>>> { key, _, cause ->
@@ -559,7 +559,7 @@ private typealias RpcReplyMap = ConcurrentHashMap<InvocationId, SettableFuture<A
 private typealias CallSiteMap = ConcurrentHashMap<InvocationId, Throwable?>
 
 /**
- * Holds a context available during Kryo deserialisation of messages that are expected to contain Observables.
+ * Holds a context available during de-serialisation of messages that are expected to contain Observables.
  *
  * @param observableMap holds the Observables that are ultimately exposed to the user.
  * @param hardReferenceStore holds references to Observables we want to keep alive while they are subscribed to.

client/rpc/src/main/kotlin/net/corda/client/rpc/internal/serialization/amqp/AMQPClientSerializationScheme.kt

@@ -14,7 +14,6 @@ import net.corda.serialization.internal.amqp.AccessOrderLinkedHashMap
 import net.corda.serialization.internal.amqp.SerializerFactory
 import net.corda.serialization.internal.amqp.amqpMagic
 import net.corda.serialization.internal.amqp.custom.RxNotificationSerializer
-import java.util.concurrent.ConcurrentHashMap
 
 /**
  * When set as the serialization scheme for a process, sets it to be the Corda AMQP implementation.
@@ -54,7 +53,7 @@ class AMQPClientSerializationScheme(
 
     override fun rpcClientSerializerFactory(context: SerializationContext): SerializerFactory {
         return SerializerFactory(context.whitelist, context.deserializationClassLoader, context.lenientCarpenterEnabled).apply {
-            register(RpcClientObservableSerializer)
+            register(RpcClientObservableDeSerializer)
             register(RpcClientCordaFutureSerializer(this))
             register(RxNotificationSerializer(this))
         }

client/rpc/src/main/kotlin/net/corda/client/rpc/internal/serialization/amqp/RpcClientObservableDeSerializer.kt

@@ -17,11 +17,11 @@ import java.util.concurrent.atomic.AtomicInteger
 import javax.transaction.NotSupportedException
 
 /**
- * Serializer for Rx[Observable] instances for the RPC Client library. Can only be used to deserialize such objects,
+ * De-serializer for Rx[Observable] instances for the RPC Client library. Can only be used to deserialize such objects,
- * just as the corresponding RPC server side code can only serialize them. Observables are only notionally serialized,
+ * just as the corresponding RPC server side code ([RpcServerObservableSerializer]) can only serialize them. Observables are only notionally serialized,
  * what is actually sent is a reference to the observable that can then be subscribed to.
  */
-object RpcClientObservableSerializer : CustomSerializer.Implements<Observable<*>>(Observable::class.java) {
+object RpcClientObservableDeSerializer : CustomSerializer.Implements<Observable<*>>(Observable::class.java) {
     private object RpcObservableContextKey
 
     fun createContext(
@@ -83,7 +83,7 @@ object RpcClientObservableSerializer : CustomSerializer.Implements<Observable<*>
         }
 
         val observableContext =
-                context.properties[RpcClientObservableSerializer.RpcObservableContextKey] as ObservableContext
+                context.properties[RpcClientObservableDeSerializer.RpcObservableContextKey] as ObservableContext
 
         if (obj !is List<*>) throw NotSerializableException("Input must be a serialised list")
         if (obj.size != 2) throw NotSerializableException("Expecting two elements, have ${obj.size}")

docs/source/clientrpc.rst

@@ -275,9 +275,12 @@ will be freed automatically.
    printed to the logs and the observable will be unsubscribed for you. But don't rely on this, as garbage collection
    is non-deterministic.
 
+.. note:: Observables can only be used as return arguments of an RPC call. It is not currently possible to pass
+Observables as parameters to the RPC methods.
+
 Futures
 -------
-A method can also return a ``ListenableFuture`` in its object graph and it will be treated in a similar manner to
+A method can also return a ``CordaFuture`` in its object graph and it will be treated in a similar manner to
 observables. Calling the ``cancel`` method on the future will unsubscribe it from any future value and release any resources.
 
 Versioning

node/src/main/kotlin/net/corda/node/serialization/amqp/RpcServerObservableSerializer.kt

@@ -65,6 +65,8 @@ class RpcServerObservableSerializer : CustomSerializer.Implements<Observable<*>>
             input: DeserializationInput,
             context: SerializationContext
     ): Observable<*> {
+        // Note: this type of server Serializer is never meant to read postings arriving from clients.
+        // I.e. Observables cannot be used as parameters for RPC methods and can only be used as return values.
         throw UnsupportedOperationException()
     }
 

node/src/test/kotlin/net/corda/node/internal/serialization/RoundTripObservableSerializerTests.kt

@@ -5,7 +5,7 @@ import com.github.benmanes.caffeine.cache.Cache
 import com.github.benmanes.caffeine.cache.Caffeine
 import com.github.benmanes.caffeine.cache.RemovalListener
 import com.nhaarman.mockito_kotlin.mock
-import net.corda.client.rpc.internal.serialization.amqp.RpcClientObservableSerializer
+import net.corda.client.rpc.internal.serialization.amqp.RpcClientObservableDeSerializer
 import net.corda.core.context.Trace
 import net.corda.core.internal.ThreadBox
 import net.corda.node.internal.serialization.testutils.AMQPRoundTripRPCSerializationScheme
@@ -90,7 +90,7 @@ class RoundTripObservableSerializerTests {
         val serverSerializationContext = RpcServerObservableSerializer.createContext(
                 serializationContext, serverObservableContext)
 
-        val clientSerializationContext = RpcClientObservableSerializer.createContext(
+        val clientSerializationContext = RpcClientObservableDeSerializer.createContext(
                 serializationContext, clientObservableContext).withProperty(RPCApi.RpcRequestOrObservableIdKey, id)
 
 

node/src/test/kotlin/net/corda/node/internal/serialization/testutils/AMQPTestSerialiationScheme.kt

@@ -1,6 +1,6 @@
 package net.corda.node.internal.serialization.testutils
 
-import net.corda.client.rpc.internal.serialization.amqp.RpcClientObservableSerializer
+import net.corda.client.rpc.internal.serialization.amqp.RpcClientObservableDeSerializer
 import net.corda.core.context.Trace
 import net.corda.core.serialization.ClassWhitelist
 import net.corda.core.serialization.SerializationContext
@@ -29,7 +29,7 @@ class AMQPRoundTripRPCSerializationScheme(
 ) {
     override fun rpcClientSerializerFactory(context: SerializationContext): SerializerFactory {
         return SerializerFactory(AllWhitelist, javaClass.classLoader).apply {
-            register(RpcClientObservableSerializer)
+            register(RpcClientObservableDeSerializer)
         }
     }
 
@@ -45,7 +45,7 @@ class AMQPRoundTripRPCSerializationScheme(
 
     fun rpcClientSerializerFactory(observableContext: ClientObservableContext, id: Trace.InvocationId) =
             rpcClientSerializerFactory(
-                    RpcClientObservableSerializer.createContext(serializationContext, observableContext)
+                    RpcClientObservableDeSerializer.createContext(serializationContext, observableContext)
                         .withProperty(RPCApi.RpcRequestOrObservableIdKey, id))
 
     fun rpcServerSerializerFactory(observableContext: TestObservableContext) =