[Feature] Use EMA for calculating averages

diff --git a/src/libserver/symbols_cache.c b/src/libserver/symbols_cache.c
index 66ae1c1b91fdd2309b78470dad6014c5952fbc07..d44b585e9d0084c48421e842afd63c5a5847af09 100644 (file)
--- a/src/libserver/symbols_cache.c
+++ b/src/libserver/symbols_cache.c
@@ -331,7 +331,7 @@ cache_logic_cmp (const void *p1, const void *p2, gpointer ud)
 }
 
 /**
- * Set counter for a symbol
+ * Set counter for a symbol using moving average
  */
 static double
 rspamd_set_counter (struct counter_data *cd, gdouble value)
@@ -351,6 +351,30 @@ rspamd_set_counter (struct counter_data *cd, gdouble value)
        return cd->mean;
 }
 
+/**
+ * Set counter for a symbol using exponential moving average
+ */
+static double
+rspamd_set_counter_ema (struct counter_data *cd, gdouble value, gdouble alpha)
+{
+       gdouble diff, incr;
+
+       /* Cumulative moving average using per-process counter data */
+       if (cd->number == 0) {
+               cd->mean = 0;
+               cd->stddev = 0;
+       }
+
+       diff = value - cd->mean;
+       incr = diff * alpha;
+       cd->mean += incr;
+       cd->stddev = (1 - alpha) * (cd->stddev + diff * incr);
+       cd->number ++;
+
+       return cd->mean;
+}
+
+
 static void
 rspamd_symbols_cache_resort (struct symbols_cache *cache)
 {
@@ -2046,11 +2070,12 @@ rspamd_symbols_cache_resort_cb (gint fd, short what, gpointer ud)
        struct cache_item *item, *parent;
        guint i;
        gdouble cur_ticks;
+       static const double decay_rate = 0.7;
 
        cache = cbdata->cache;
        /* Plan new event */
        tm = rspamd_time_jitter (cache->reload_time, 0);
-       cur_ticks = rspamd_get_ticks (TRUE);
+       cur_ticks = rspamd_get_ticks (FALSE);
        msg_debug_cache ("resort symbols cache, next reload in %.2f seconds", tm);
        g_assert (cache != NULL);
        evtimer_set (&cbdata->resort_ev, rspamd_symbols_cache_resort_cb, cbdata);
@@ -2071,8 +2096,8 @@ rspamd_symbols_cache_resort_cb (gint fd, short what, gpointer ud)
 
                                cur_value = (item->st->total_hits - item->last_count) /
                                                (cur_ticks - cbdata->last_resort);
-                               rspamd_set_counter (&item->st->frequency_counter,
-                                               cur_value);
+                               rspamd_set_counter_ema (&item->st->frequency_counter,
+                                               cur_value, decay_rate);
                                item->st->avg_frequency = item->st->frequency_counter.mean;
                                item->st->stddev_frequency = item->st->frequency_counter.stddev;
 
@@ -2111,8 +2136,8 @@ rspamd_symbols_cache_resort_cb (gint fd, short what, gpointer ud)
                        if (item->cd->number > 0) {
                                if (item->type & (SYMBOL_TYPE_CALLBACK|SYMBOL_TYPE_NORMAL)) {
                                        item->st->avg_time = item->cd->mean;
-                                       rspamd_set_counter (&item->st->time_counter,
-                                                       item->st->avg_time);
+                                       rspamd_set_counter_ema (&item->st->time_counter,
+                                                       item->st->avg_time, decay_rate);
                                        item->st->avg_time = item->st->time_counter.mean;
                                        memset (item->cd, 0, sizeof (*item->cd));
                                }