Merge pull request #25 from rabbitmq/echo-flow-state

Add function to request flow state from sender

deps/amqp10_client/src/amqp10_client.erl

@@ -47,6 +47,7 @@
          accept_msg/2,
          flow_link_credit/3,
          flow_link_credit/4,
+         echo/1,
          link_handle/1,
          get_msg/1,
          get_msg/2,
@@ -299,6 +300,15 @@ flow_link_credit(#link_ref{role = receiver, session = Session,
                         drain = Drain},
     ok = amqp10_client_session:flow(Session, Handle, Flow, RenewWhenBelow).
 
+%% @doc Request that the sender's flow state is echoed back
+%% This may be used to determine when the Link has finally quiesced.
+%% see §2.6.10 of the spec
+echo(#link_ref{role = receiver, session = Session,
+               link_handle = Handle}) ->
+    Flow = #'v1_0.flow'{link_credit = {uint, 0},
+                        echo = true},
+    ok = amqp10_client_session:flow(Session, Handle, Flow, 0).
+
 %%% messages
 
 %% @doc Send a message on a the link referred to be the 'LinkRef'.