Update pipe_verify_handoff_blocking to handle the occasional error where

a vnode has been transferred after the vnode proxy has gotten its pid
but before the work can be sent.

Author: Doug Rohrer

tests/pipe_verify_handoff_blocking.erl

@@ -43,17 +43,6 @@
 %% archive), but we don't want them to process so many inputs that
 %% they consume their blocking queues before handing off.
 
-%% Please Note: Under rare circumstances, this test may fail with a 
-%% "{badmatch,{error,[{vnode_down,noproc}]}}' error. This is not a 
-%% failure of this test but rather a side effect of a race condition 
-%% in riak_core_vnode_proxy. It manifests due to the fact that the
-%% test is attempting to send a command to a vnode that is in fact 
-%% down, however monitor only works by issuing a command and getting
-%% a PID. In some instances, get_vnode_pid fails because vnode shutdown
-%% is queued up in the mailbox before monitor node. Unfortunately, the
-%% fix would require a fundamental shift in the architecture of
-%% riak_core, which at the time of this writing is not feasible for
-%% this rare failure case.
 -module(pipe_verify_handoff_blocking).
 
 -export([
@@ -175,7 +164,11 @@ queue_filler(Node, Pipe, Inputs, Count) ->
         {stop, Owner} -> Owner ! {done, Count}
     after 0 ->
             {{value, I}, Q} = queue:out(Inputs),
-            ok = rpc:call(Node, riak_pipe, queue_work, [Pipe, I]),
+            case rpc:call(Node, riak_pipe, queue_work, [Pipe, I]) of
+                ok -> ok;
+                {error,[{vnode_down,noproc}]} -> ok; %% OK if vnode has moved to different node - next request should succeed
+                Other -> throw(Other)
+            end,
             queue_filler(Node, Pipe, queue:in(I, Q), Count+1)
     end.