From 068c1481ab389d8d781dff2a3fd2860bb735e844 Mon Sep 17 00:00:00 2001
From: Russell Brown <russell.brown@mac.com>
Date: Fri, 14 Jun 2013 10:00:08 +0100
Subject: [PATCH] Fix crash when vnode Pid vanishes during stat calc

---
 src/riak_core_stat.erl | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/riak_core_stat.erl b/src/riak_core_stat.erl
index 377922b1c..1a1900f2d 100644
--- a/src/riak_core_stat.erl
+++ b/src/riak_core_stat.erl
@@ -169,13 +169,20 @@ safe_trunc(X) ->
 %% Provide aggregate stats for vnode queues.  Compute instantaneously for now,
 %% may need to cache if stats are called heavily (multiple times per seconds)
 vnodeq_stats() ->
-    VnodesInfo = [{Service, element(2, erlang:process_info(Pid, message_queue_len))} ||
+    VnodesInfo = [{Service, vnodeq_len(Pid)} ||
                      {Service, _Index, Pid} <- riak_core_vnode_manager:all_vnodes()],
     ServiceInfo = lists:foldl(fun({S,MQL}, A) ->
                                       orddict:append_list(S, [MQL], A)
                               end, orddict:new(), VnodesInfo),
     lists:flatten([vnodeq_aggregate(S, MQLs) || {S, MQLs} <- ServiceInfo]).
 
+vnodeq_len(Pid) ->
+    try
+        element(2, erlang:process_info(Pid, message_queue_len))
+    catch _ ->
+            0
+    end.
+
 vnodeq_aggregate(_Service, []) ->
     []; % no vnodes, no stats
 vnodeq_aggregate(Service, MQLs0) ->