Make AsyncProcessor::processInteraction pure virtual

Summary: `processInteraction()` is part of the critical path for interactions in Resource Pools and can lead to undefined behavior if it is not implemented. Let's make the contract more clear and force custom `AsyncProcessor` implementations to provide an implementation for it.

Reviewed By: tlj77

Differential Revision: D62590107

fbshipit-source-id: 69fe9e9bee745766d891b5fc5f33d9953d6845eb

server/cpp/HaskellProcessor.h

@@ -56,6 +56,12 @@ class HaskellAsyncProcessor : public AsyncProcessor {
       ServerRequest&& request,
       const AsyncProcessorFactory::MethodMetadata& methodMetadata) override;
 
+  void processInteraction(ServerRequest&&) override {
+    LOG(FATAL)
+        << "This AsyncProcessor doesn't support Thrift interactions. "
+        << "Please implement processInteraction to support interactions.";
+  }
+
  protected:
   TCallback callback_;
   AsyncProcessorFactory::MethodMetadataMap& metadataMap_;