stats: send real last value if no new values come
Background:
* Individual values can be added to osmo_stat_item.values at any time.
* Stats are reported at a fixed interval (see vty 'stats interval'),
e.g. every 10 seconds.
* In order to report a new stat value, we use the maximum of all
osmo_stat_item.values added since the last report.
* By default, we do not send new stat values if they did not change
(see vty 'config-stats' -> 'flush-period' default of 0).
Fix the following bug:
* If 'flush-period' is 0, and no new osmo_stat_item.values are coming
in, the last value that gets reported is not necessarily the last
entry in osmo_stat_item.values.
* For attached reporters (statsd), it could then be that the given stat
stays at the wrong value for a long stretch of time (think of several
hours/days/forever).
Explanation of how the test shows that it is fixed:
* stats get reported (value is irrelevant)
* osmo_stat_item gets a new value: 20
* osmo_stat_item gets a new value: 10
* stats get reported (value: 20, the maximum of both new values)
* osmo_stat_item gets no new values
* stats get reported (value: 10, this is new because of the bug fix,
the real last value in osmo_stat_item, different from the 20 sent
earlier, without the fix it would not send anything here and the last
sent value would be 20)
* osmo_stat_item gets no new values
* stats get reported (nothing gets sent, since the real last value was
already sent and 'flush-period' is 0)
Fixes: OS#5215
Change-Id: Ibeefd0e3d1dbe4be454ff05a21df4848b2abfabe
diff --git a/src/stats.c b/src/stats.c
index 411ecff..f06515d 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -715,6 +715,11 @@
if (!have_value) {
/* Send the last value in case a flush is requested */
value = osmo_stat_item_get_last(item);
+
+ /* Also send it in case a different max value was sent
+ * previously (OS#5215) */
+ if (!item->stats_last_sent_was_max)
+ have_value = 1;
} else {
int32_t next_val;
/* If we have multiple values only send the max */
@@ -722,6 +727,8 @@
value = OSMO_MAX(value, next_val);
}
+ item->stats_last_sent_was_max = (osmo_stat_item_get_last(item) == value);
+
llist_for_each_entry(srep, &osmo_stats_reporter_list, list) {
if (!srep->running)
continue;