1 files changed, 73 insertions, 1 deletions

diff --git a/src/feature/relay/relay_metrics.c b/src/feature/relay/relay_metrics.c
index 3d392847e1..2686249548 100644
--- a/src/feature/relay/relay_metrics.c
+++ b/src/feature/relay/relay_metrics.c
@@ -10,6 +10,9 @@
 
 #include "orconfig.h"
 
+#include "core/or/or.h"
+#include "core/or/relay.h"
+
 #include "lib/malloc/malloc.h"
 #include "lib/container/smartlist.h"
 #include "lib/metrics/metrics_store.h"
@@ -17,16 +20,78 @@
 
 #include "feature/relay/relay_metrics.h"
 
+/** Declarations of each fill function for metrics defined in base_metrics. */
+static void fill_oom_values(void);
+
 /** The base metrics that is a static array of metrics added to the metrics
  * store.
  *
  * The key member MUST be also the index of the entry in the array. */
-static const relay_metrics_entry_t base_metrics[] = {};
+static const relay_metrics_entry_t base_metrics[] =
+{
+  {
+    .key = RELAY_METRICS_NUM_OOM_BYTES,
+    .type = METRICS_TYPE_COUNTER,
+    .name = METRICS_NAME(relay_load_oom_bytes_total),
+    .help = "Total number of bytes the OOM has freed by subsystem",
+    .fill_fn = fill_oom_values,
+  },
+};
 static const size_t num_base_metrics = ARRAY_LENGTH(base_metrics);
 
 /** The only and single store of all the relay metrics. */
 static metrics_store_t *the_store;
 
+/** Fill function for the RELAY_METRICS_NUM_OOM_BYTES metrics. */
+static void
+fill_oom_values(void)
+{
+  metrics_store_entry_t *sentry;
+  const relay_metrics_entry_t *rentry =
+    &base_metrics[RELAY_METRICS_NUM_OOM_BYTES];
+
+  sentry = metrics_store_add(the_store, rentry->type, rentry->name,
+                             rentry->help);
+  metrics_store_entry_add_label(sentry, "subsys=cell");
+  metrics_store_entry_update(sentry, oom_stats_n_bytes_removed_cell);
+
+  sentry = metrics_store_add(the_store, rentry->type, rentry->name,
+                             rentry->help);
+  metrics_store_entry_add_label(sentry, "subsys=dns");
+  metrics_store_entry_update(sentry, oom_stats_n_bytes_removed_dns);
+
+  sentry = metrics_store_add(the_store, rentry->type, rentry->name,
+                             rentry->help);
+  metrics_store_entry_add_label(sentry, "subsys=geoip");
+  metrics_store_entry_update(sentry, oom_stats_n_bytes_removed_geoip);
+
+  sentry = metrics_store_add(the_store, rentry->type, rentry->name,
+                             rentry->help);
+  metrics_store_entry_add_label(sentry, "subsys=hsdir");
+  metrics_store_entry_update(sentry, oom_stats_n_bytes_removed_hsdir);
+}
+
+/** Reset the global store and fill it with all the metrics from base_metrics
+ * and their associated values.
+ *
+ * To pull this off, every metrics has a "fill" function that is called and in
+ * charge of adding the metrics to the store, appropriate labels and finally
+ * updating the value to report. */
+static void
+fill_store(void)
+{
+  /* Reset the current store, we are about to fill it with all the things. */
+  metrics_store_reset(the_store);
+
+  /* Call the fill function for each metrics. */
+  for (size_t i = 0; i < num_base_metrics; i++) {
+    if (BUG(!base_metrics[i].fill_fn)) {
+      continue;
+    }
+    base_metrics[i].fill_fn();
+  }
+}
+
 /** Return a list of all the relay metrics stores. This is the
  * function attached to the .get_metrics() member of the subsys_t. */
 const smartlist_t *
@@ -36,6 +101,13 @@ relay_metrics_get_stores(void)
    * simply update it. */
   static smartlist_t *stores_list = NULL;
 
+  /* We dynamically fill the store with all the metrics upon a request. The
+   * reason for this is because the exposed metrics of a relay are often
+   * internal counters in the fast path and thus we fetch the value when a
+   * metrics port request arrives instead of keeping a local metrics store of
+   * those values. */
+  fill_store();
+
   if (!stores_list) {
     stores_list = smartlist_new();
     smartlist_add(stores_list, the_store);