metrics: Add tor_ namespace to all metrics

Closes #40063
Signed-off-by: David Goulet <dgoulet@torproject.org>

src/feature/hs/hs_metrics_entry.c

@@ -23,40 +23,40 @@ const hs_metrics_entry_t base_metrics[] =
   {
     .key = HS_METRICS_NUM_INTRODUCTIONS,
     .type = METRICS_TYPE_COUNTER,
-    .name = "hs_intro_num_total",
+    .name = METRICS_NAME(hs_intro_num_total),
     .help = "Total number of introduction received",
     .port_as_label = false,
   },
   {
     .key = HS_METRICS_APP_WRITE_BYTES,
     .type = METRICS_TYPE_COUNTER,
-    .name = "hs_app_write_bytes_total",
+    .name = METRICS_NAME(hs_app_write_bytes_total),
     .help = "Total number of bytes written to the application",
     .port_as_label = true,
   },
   {
     .key = HS_METRICS_APP_READ_BYTES,
     .type = METRICS_TYPE_COUNTER,
-    .name = "hs_app_read_bytes_total",
+    .name = METRICS_NAME(hs_app_read_bytes_total),
     .help = "Total number of bytes read from the application",
     .port_as_label = true,
   },
   {
     .key = HS_METRICS_NUM_ESTABLISHED_RDV,
     .type = METRICS_TYPE_GAUGE,
-    .name = "hs_rdv_established_count",
+    .name = METRICS_NAME(hs_rdv_established_count),
     .help = "Total number of established rendezvous circuit",
   },
   {
     .key = HS_METRICS_NUM_RDV,
     .type = METRICS_TYPE_COUNTER,
-    .name = "hs_rdv_num_total",
+    .name = METRICS_NAME(hs_rdv_num_total),
     .help = "Total number of rendezvous circuit created",
   },
   {
     .key = HS_METRICS_NUM_ESTABLISHED_INTRO,
     .type = METRICS_TYPE_GAUGE,
-    .name = "hs_intro_established_count",
+    .name = METRICS_NAME(hs_intro_established_count),
     .help = "Total number of established introduction circuit",
   },
 };

src/lib/metrics/metrics_common.h

@@ -11,6 +11,15 @@
 
 #include "lib/cc/torint.h"
 
+/** Prefix to every metrics exposed. This is insures that the metrics are
+ * always in the same namespace. */
+#define METRICS_PREFIX tor_
+
+/** Helper macro that must be used to construct the right namespaced metrics
+ * name. A name is a string so stringify the result. */
+#define METRICS_STR(val) #val
+#define METRICS_NAME(name) METRICS_STR(METRICS_PREFIX ## name)
+
 /** Format output type. */
 typedef enum {
   /** Prometheus data output format. */