refactor stat_item: report only changed values

Change the functionality of skipping unchanged values: instead of
looking up whether new values have been set on a stat item, rather
remember the last reported value and skip reporting identical values.

stats_test.c shows that previously, a stat item reported a value of 10
again, even though the previous report had already sent a value of 10.
That's just because the value 10 was explicitly set again, internally.

From a perspective of preserving all data points, it could make sense to
send consecutive identical values. But since we already collapse all
data points per reporting period into a max, that is pointless.

Related: SYS#5542
Change-Id: I8f4cf34dfed17e0879716fa2cbeee137c158978b

1 files changed, 2 insertions, 4 deletions

diff --git a/tests/stats/stats_test.err b/tests/stats/stats_test.err
index a890e0fa..1e604d19 100644
--- a/tests/stats/stats_test.err
+++ b/tests/stats/stats_test.err
@@ -114,10 +114,8 @@ report (group 1, item 1 update):
   test2: item p= g=test.one i=1 n=item.a v=10 u=ma
   test1: item p= g=test.one i=1 n=item.a v=10 u=ma
 reported: 0 counter vals, 2 stat item vals
-report (group 1, item 1 update twice):
-  test2: item p= g=test.one i=1 n=item.a v=10 u=ma
-  test1: item p= g=test.one i=1 n=item.a v=10 u=ma
-reported: 0 counter vals, 2 stat item vals
+report (group 1, item 1 update twice, with same value):
+reported: 0 counter vals, 0 stat item vals
 report (group 1, item 1 update twice, check max):
   test2: item p= g=test.one i=1 n=item.a v=20 u=ma
   test1: item p= g=test.one i=1 n=item.a v=20 u=ma