add a stats counter for clients dropped due to recursive-clients limit

(cherry picked from commit 715afa9c57)

CHANGES

@@ -1,3 +1,7 @@
+5327.	[func]		Added a statistics counter to track queries
+			dropped because the recursive-clients quota was
+			exceeded. [GL #1399]
+
 5326.	[bug]		Add python dependancy on 'distutils.core' to configure.
 			'distutils.core' is required for installation.
 			[GL #1397]

bin/named/statschannel.c

@@ -317,6 +317,9 @@ init_desc(void) {
 		       "QryUsedStale");
 	SET_NSSTATDESC(prefetch, "queries triggered prefetch", "Prefetch");
 	SET_NSSTATDESC(keytagopt, "Keytag option received", "KeyTagOpt");
+	SET_NSSTATDESC(reclimitdropped,
+		       "queries dropped due to recursive client limit",
+		       "RecLimitDropped");
 
 	INSIST(i == ns_statscounter_max);
 

bin/tests/system/fetchlimit/tests.sh

@@ -179,5 +179,17 @@ echo_i "clients count exceeded 380 on $exceeded trials (expected 0)"
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=`expr $status + $ret`
 
+echo_i "checking drop statistics"
+rm -f ns3/named.stats
+$RNDCCMD stats
+for try in 1 2 3 4 5; do
+    [ -f ns3/named.stats ] && break
+    sleep 1
+done
+drops=`grep 'queries dropped due to recursive client limit' ns3/named.stats | sed 's/\([0-9][0-9]*\) queries.*/\1/'`
+[ "${drops:-0}" -ne 0 ] || ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=`expr $status + $ret`
+
 echo_i "exit status: $status"
 [ $status -eq 0 ] || exit 1

lib/ns/client.c

@@ -278,8 +278,11 @@ ns_client_killoldestquery(ns_client_t *client) {
 		ISC_LIST_UNLINK(client->manager->recursing, oldest, rlink);
 		UNLOCK(&client->manager->reclock);
 		ns_query_cancel(oldest);
-	} else
+		ns_stats_increment(client->sctx->nsstats,
+				   ns_statscounter_reclimitdropped);
+	} else {
 		UNLOCK(&client->manager->reclock);
+	}
 }
 
 void

lib/ns/include/ns/stats.h

@@ -104,7 +104,9 @@ enum {
 
 	ns_statscounter_tcphighwater = 65,
 
-	ns_statscounter_max = 66,
+	ns_statscounter_reclimitdropped = 66,
+
+	ns_statscounter_max = 67,
 };
 
 void