1 files changed, 92 insertions, 0 deletions
diff --git a/src/web/api/queries/ses/ses.h b/src/web/api/queries/ses/ses.h
new file mode 100644
index 000000000..de8645ff0
--- /dev/null
+++ b/src/web/api/queries/ses/ses.h
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_API_QUERIES_SES_H
+#define NETDATA_API_QUERIES_SES_H
+
+#include "../query.h"
+#include "../rrdr.h"
+
+struct tg_ses {
+    NETDATA_DOUBLE alpha;
+    NETDATA_DOUBLE alpha_other;
+    NETDATA_DOUBLE level;
+    size_t count;
+};
+
+static size_t tg_ses_max_window_size = 15;
+
+static inline void tg_ses_init(void) {
+    long long ret = config_get_number(CONFIG_SECTION_WEB, "ses max tg_des_window", (long long)tg_ses_max_window_size);
+    if(ret <= 1) {
+        config_set_number(CONFIG_SECTION_WEB, "ses max tg_des_window", (long long)tg_ses_max_window_size);
+    }
+    else {
+        tg_ses_max_window_size = (size_t) ret;
+    }
+}
+
+static inline NETDATA_DOUBLE tg_ses_window(RRDR *r, struct tg_ses *g) {
+    (void)g;
+
+    NETDATA_DOUBLE points;
+    if(r->view.group == 1) {
+        // provide a running DES
+        points = (NETDATA_DOUBLE)r->time_grouping.points_wanted;
+    }
+    else {
+        // provide a SES with flush points
+        points = (NETDATA_DOUBLE)r->view.group;
+    }
+
+    return (points > (NETDATA_DOUBLE)tg_ses_max_window_size) ? (NETDATA_DOUBLE)tg_ses_max_window_size : points;
+}
+
+static inline void tg_ses_set_alpha(RRDR *r, struct tg_ses *g) {
+    // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
+    // A commonly used value for alpha is 2 / (N + 1)
+    g->alpha = 2.0 / (tg_ses_window(r, g) + 1.0);
+    g->alpha_other = 1.0 - g->alpha;
+}
+
+static inline void tg_ses_create(RRDR *r, const char *options __maybe_unused) {
+    struct tg_ses *g = (struct tg_ses *)onewayalloc_callocz(r->internal.owa, 1, sizeof(struct tg_ses));
+    tg_ses_set_alpha(r, g);
+    g->level = 0.0;
+    r->time_grouping.data = g;
+}
+
+// resets when switches dimensions
+// so, clear everything to restart
+static inline void tg_ses_reset(RRDR *r) {
+    struct tg_ses *g = (struct tg_ses *)r->time_grouping.data;
+    g->level = 0.0;
+    g->count = 0;
+}
+
+static inline void tg_ses_free(RRDR *r) {
+    onewayalloc_freez(r->internal.owa, r->time_grouping.data);
+    r->time_grouping.data = NULL;
+}
+
+static inline void tg_ses_add(RRDR *r, NETDATA_DOUBLE value) {
+    struct tg_ses *g = (struct tg_ses *)r->time_grouping.data;
+
+    if(unlikely(!g->count))
+        g->level = value;
+
+    g->level = g->alpha * value + g->alpha_other * g->level;
+    g->count++;
+}
+
+static inline NETDATA_DOUBLE tg_ses_flush(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
+    struct tg_ses *g = (struct tg_ses *)r->time_grouping.data;
+
+    if(unlikely(!g->count || !netdata_double_isnumber(g->level))) {
+        *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
+        return 0.0;
+    }
+
+    return g->level;
+}
+
+#endif //NETDATA_API_QUERIES_SES_H