default void postEndpointInvocation(ObserverContext<? extends RegionCoprocessorEnvironment> ctx,
    Service service, String methodName, Message request, Message.Builder responseBuilder)
    throws IOException {
  }
Called after an Endpoint service method is invoked. The response message can be altered using
the builder.
@param ctx             the environment provided by the region server
@param service         the endpoint service
@param methodName      the invoked service method
@param request         Request message expected by given {@code Service}'s method (by the name
                       {@code methodName}).
@param responseBuilder Builder for final response to the client, with original response from
                       Service's method merged into it.
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/EndpointObserver.java