relay: Add the global connection limit metrics

This emits two events (read and write) of the total number that the
global connection limit was reached.

Related to #40367

Signed-off-by: David Goulet <dgoulet@torproject.org>

2 files changed, 24 insertions, 0 deletions

diff --git a/src/feature/stats/rephist.c b/src/feature/stats/rephist.c
index 98907055ef..920a96a39a 100644
--- a/src/feature/stats/rephist.c
+++ b/src/feature/stats/rephist.c
@@ -207,6 +207,11 @@ typedef struct {
 /** Current state of overload stats */
 static overload_stats_t overload_stats;
 
+/** Counters to count the number of times we've reached an overload for the
+ * global connection read/write limit. Reported on the MetricsPort. */
+static uint64_t stats_n_read_limit_reached = 0;
+static uint64_t stats_n_write_limit_reached = 0;
+
 /** Return true if this overload happened within the last `n_hours`. */
 static bool
 overload_happened_recently(time_t overload_time, int n_hours)
@@ -221,6 +226,20 @@ overload_happened_recently(time_t overload_time, int n_hours)
 /* The current version of the overload stats version */
 #define OVERLOAD_STATS_VERSION 1
 
+/** Return the stats_n_read_limit_reached counter. */
+uint64_t
+rep_hist_get_n_read_limit_reached(void)
+{
+  return stats_n_read_limit_reached;
+}
+
+/** Return the stats_n_write_limit_reached counter. */
+uint64_t
+rep_hist_get_n_write_limit_reached(void)
+{
+  return stats_n_write_limit_reached;
+}
+
 /** Returns an allocated string for server descriptor for publising information
  * on whether we are overloaded or not. */
 char *
@@ -299,6 +318,7 @@ rep_hist_note_overload(overload_type_t overload)
     SET_TO_START_OF_HOUR(overload_stats.overload_general_time);
     break;
   case OVERLOAD_READ: {
+    stats_n_read_limit_reached++;
     SET_TO_START_OF_HOUR(overload_stats.overload_ratelimits_time);
     if (approx_time() >= last_read_counted + 60) { /* Count once a minute */
         overload_stats.overload_read_count++;
@@ -307,6 +327,7 @@ rep_hist_note_overload(overload_type_t overload)
     break;
   }
   case OVERLOAD_WRITE: {
+    stats_n_write_limit_reached++;
     SET_TO_START_OF_HOUR(overload_stats.overload_ratelimits_time);
     if (approx_time() >= last_write_counted + 60) { /* Count once a minute */
       overload_stats.overload_write_count++;
diff --git a/src/feature/stats/rephist.h b/src/feature/stats/rephist.h
index 0bb9dd4678..b54fc77883 100644
--- a/src/feature/stats/rephist.h
+++ b/src/feature/stats/rephist.h
@@ -162,6 +162,9 @@ void rep_hist_note_overload(overload_type_t overload);
 char *rep_hist_get_overload_general_line(void);
 char *rep_hist_get_overload_stats_lines(void);
 
+uint64_t rep_hist_get_n_read_limit_reached(void);
+uint64_t rep_hist_get_n_write_limit_reached(void);
+
 #ifdef TOR_UNIT_TESTS
 struct hs_v2_stats_t;
 const struct hs_v2_stats_t *rep_hist_get_hs_v2_stats(void);