We currently use some custom commands with Infinispan. We have since moved over to wanting to use a custom command with a return value for the response.

We have tried using the various methods on the RpcManager and have found a few issues.

1. Map<Address, Response> invokeRemotely(Collection<Address> recipients, ReplicableCommand rpc, boolean sync, boolean usePriorityQueue) throws RpcException;

This method always returns a null for cluster responses. This is a simple issue that can be solved with the following diff

diff --git a/core/src/main/java/org/infinispan/commands/remote/SingleRpcCommand.
index bf369bc..79bc02e 100644
--- a/core/src/main/java/org/infinispan/commands/remote/SingleRpcCommand.java
+++ b/core/src/main/java/org/infinispan/commands/remote/SingleRpcCommand.java
@@ -107,6 +107,6 @@ public ReplicableCommand getCommand() {
 
    @Override
    public boolean isReturnValueExpected() {
-      return false;
+      return command.isReturnValueExpected();
    }
 }

The SingleRpcCommand wraps the given command always forcing the return value expectation to be false.

2. Map<Address, Response> invokeRemotely(Collection<Address> recipients, ReplicableCommand rpcCommand, ResponseMode mode, long timeout);

This method doesn't wrap the return value in a Response thus causing a ClassCastException when the client node gets the response back. I haven't looked into detail with this one yet.

If needed I can send a sample project that shows the behavior.