relay: Add the OOM invocation metrics

With this commit, a relay now emits metrics event on the MetricsPort
related to the OOM invocation for:

  - DNS cache
  - GeoIP database
  - Cell queues
  - HSDir caches

Everytime the OOM is invoked, the number of bytes is added to the
metrics counter for that specific type of invocation.

Related to #40367

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

1 files changed, 4 insertions, 6 deletions

diff --git a/src/feature/relay/relay_metrics.h b/src/feature/relay/relay_metrics.h
index 7bc4760916..7d644badd3 100644
--- a/src/feature/relay/relay_metrics.h
+++ b/src/feature/relay/relay_metrics.h
@@ -12,13 +12,11 @@
 #include "lib/container/smartlist.h"
 #include "lib/metrics/metrics_common.h"
 
-#ifdef RELAY_METRICS_ENTRY_PRIVATE
-
 /** Metrics key for each reported metrics. This key is also used as an index in
  * the base_metrics array. */
 typedef enum {
-  /* XXX So code compiles. */
-  PLACEHOLDER = 0,
+  /** Number of OOM invocation. */
+  RELAY_METRICS_NUM_OOM_BYTES = 0,
 } relay_metrics_key_t;
 
 /** The metadata of a relay metric. */
@@ -31,10 +29,10 @@ typedef struct relay_metrics_entry_t {
   const char *name;
   /* Metrics output help comment. */
   const char *help;
+  /* Update value function. */
+  void (*fill_fn)(void);
 } relay_metrics_entry_t;
 
-#endif /* RELAY_METRICS_ENTRY_PRIVATE */
-
 /* Init. */
 void relay_metrics_init(void);
 void relay_metrics_free(void);