Merge branch '4668-request-to-add-a-new-statistic-recursive-client-high-water-in-rndc-status-and-stats-channel' into 'main'

Add new statistics variable for recursive client high-water

Closes #4668

See merge request isc-projects/bind9!9023

CHANGES

@@ -1,3 +1,8 @@
+6387.	[func]		Added a new statistics variable "recursive high-water"
+			that reports the maximum number of simultaneous
+			recursive clients BIND has handled while running.
+			[GL #4668]
+
 6386.	[bug]		When shutting down catzs->view could point to freed
 			memory. Obtain a reference to the view to prevent this.
 			[GL #4502]

bin/named/server.c

@@ -12184,6 +12184,12 @@ named_server_status(named_server_t *server, isc_buffer_t **text) {
 		 isc_quota_getmax(&server->sctx->recursionquota));
 	CHECK(putstr(text, line));
 
+	snprintf(line, sizeof(line), "recursive high-water: %u\n",
+		 (unsigned int)ns_stats_get_counter(
+			 server->sctx->nsstats,
+			 ns_statscounter_recurshighwater));
+	CHECK(putstr(text, line));
+
 	snprintf(line, sizeof(line), "tcp clients: %u/%u\n",
 		 isc_quota_getused(&server->sctx->tcpquota),
 		 isc_quota_getmax(&server->sctx->tcpquota));

bin/named/statschannel.c

@@ -327,6 +327,8 @@ init_desc(void) {
 	SET_NSSTATDESC(updatebadprereq,
 		       "updates rejected due to prerequisite failure",
 		       "UpdateBadPrereq");
+	SET_NSSTATDESC(recurshighwater, "Recursive clients high-water",
+		       "RecursHighwater");
 	SET_NSSTATDESC(recursclients, "recursing clients", "RecursClients");
 	SET_NSSTATDESC(dns64, "queries answered by DNS64", "DNS64");
 	SET_NSSTATDESC(ratedropped, "responses dropped for rate limits",

doc/notes/notes-current.rst

@@ -20,7 +20,9 @@ Security Fixes
 New Features
 ~~~~~~~~~~~~
 
-- None.
+- Added a new statistics variable ``recursive high-water`` that reports
+  the maximum number of simultaneous recursive clients BIND has handled
+  while running. :gl:`#4668`
 
 Removed Features
 ~~~~~~~~~~~~~~~~

lib/isc/include/isc/stats.h

@@ -137,10 +137,10 @@ isc_stats_ncounters(isc_stats_t *stats);
  *
  */
 
-void
+isc_statscounter_t
 isc_stats_increment(isc_stats_t *stats, isc_statscounter_t counter);
 /*%<
- * Increment the counter-th counter of stats.
+ * Increment the counter-th counter of stats and return the old value.
  *
  * Requires:
  *\li	'stats' is a valid isc_stats_t.

lib/isc/stats.c

@@ -97,12 +97,12 @@ isc_stats_create(isc_mem_t *mctx, isc_stats_t **statsp, int ncounters) {
 	*statsp = stats;
 }
 
-void
+isc_statscounter_t
 isc_stats_increment(isc_stats_t *stats, isc_statscounter_t counter) {
 	REQUIRE(ISC_STATS_VALID(stats));
 	REQUIRE(counter < stats->ncounters);
 
-	atomic_fetch_add_relaxed(&stats->counters[counter], 1);
+	return (atomic_fetch_add_relaxed(&stats->counters[counter], 1));
 }
 
 void

lib/ns/include/ns/stats.h

@@ -112,7 +112,9 @@ enum {
 
 	ns_statscounter_updatequota = 67,
 
-	ns_statscounter_max = 68,
+	ns_statscounter_recurshighwater = 68,
+
+	ns_statscounter_max = 69,
 };
 
 void
@@ -124,7 +126,7 @@ ns_stats_detach(ns_stats_t **statsp);
 void
 ns_stats_create(isc_mem_t *mctx, int ncounters, ns_stats_t **statsp);
 
-void
+isc_statscounter_t
 ns_stats_increment(ns_stats_t *stats, isc_statscounter_t counter);
 
 void

lib/ns/query.c

@@ -2483,6 +2483,7 @@ free_fresp(ns_client_t *client, dns_fetchresponse_t **frespp) {
 
 static isc_result_t
 recursionquotatype_attach(ns_client_t *client, bool soft_limit) {
+	isc_statscounter_t recurscount;
 	isc_result_t result;
 
 	result = isc_quota_acquire(&client->manager->sctx->recursionquota);
@@ -2505,8 +2506,12 @@ recursionquotatype_attach(ns_client_t *client, bool soft_limit) {
 		return (result);
 	}
 
-	ns_stats_increment(client->manager->sctx->nsstats,
-			   ns_statscounter_recursclients);
+	recurscount = ns_stats_increment(client->manager->sctx->nsstats,
+					 ns_statscounter_recursclients);
+
+	ns_stats_update_if_greater(client->manager->sctx->nsstats,
+				   ns_statscounter_recurshighwater,
+				   recurscount + 1);
 
 	return (result);
 }

lib/ns/stats.c

@@ -78,11 +78,11 @@ ns_stats_create(isc_mem_t *mctx, int ncounters, ns_stats_t **statsp) {
 /*%
  * Increment/Decrement methods
  */
-void
+isc_statscounter_t
 ns_stats_increment(ns_stats_t *stats, isc_statscounter_t counter) {
 	REQUIRE(NS_STATS_VALID(stats));
 
-	isc_stats_increment(stats->counters, counter);
+	return (isc_stats_increment(stats->counters, counter));
 }
 
 void