Rework stats to avoid concurrent read and write

Counters read by diameter:service_info(SvcName, transport) can be
selected at the same time as the diameter_stats server is folding them
into another key, possibly resulting in inaccurate values. Have
diameter_stats select from the server process to avoid this and add
diameter_stats:sum/1 to sum values from all contributors on a given
term.

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/diameter/test/diameter_stats_SUITE.erl b/lib/diameter/test/diameter_stats_SUITE.erl
index af52afb59c..76ff764671 100644
--- a/lib/diameter/test/diameter_stats_SUITE.erl
+++ b/lib/diameter/test/diameter_stats_SUITE.erl
@@ -33,6 +33,7 @@
 -export([reg/1,
          incr/1,
          read/1,
+         sum/1,
          flush/1]).
 
 -define(stat, diameter_stats).
@@ -53,6 +54,7 @@ tc() ->
     [reg,
      incr,
      read,
+     sum,
      flush].
 
 init_per_suite(Config) ->
@@ -98,6 +100,23 @@ read(_) ->
     [] = ?stat:read([make_ref()]),
     ?stat:flush([self(), Ref, make_ref()]).
 
+sum(_) ->
+    Ref = make_ref(),
+    C1 = {a,b},
+    C2 = {b,a},
+    true = ?stat:reg(Ref),
+    1 = ?stat:incr(C1),
+    1 = ?stat:incr(C2),
+    2 = ?stat:incr(C2),
+    7 = ?stat:incr(C1, Ref, 7),
+    [{Ref,  [{C1,8}, {C2,2}]}]
+        = ?stat:sum([Ref, make_ref()]),
+    Self = self(),
+    [{Self,  [{C1,1}, {C2,2}]}]
+        = ?stat:sum([self()]),
+    [{Ref, [{C1,7}]}, {Self, [{C1,1}, {C2,2}]}]
+        = lists:sort(?stat:flush([self(), Ref])).
+
 flush(_) ->
     Ref = make_ref(),
     Ctr = '_',