[master] increase and allow configuration of lwresd tasks/clients

3852.	[func]		Increase the default number of clients available
			for servicing lightweight resolver queries, and
			make them configurable via the "lwres-tasks" and
			"lwres-clients" options.  (Thanks to Tomas Hozza.)
			[RT #35857]

CHANGES

@@ -1,3 +1,9 @@
+3852.	[func]		Increase the default number of clients available
+			for servicing lightweight resolver queries, and
+			make them configurable via the "lwres-tasks" and
+			"lwres-clients" options.  (Thanks to Tomas Hozza.)
+			[RT #35857]
+
 3851.	[func]		Allow libseccomp based system-call filtering
 			on Linux; use "configure --enable-seccomp" to
 			turn it on.  Thanks to Loganaden Velvindron for

bin/named/include/named/lwresd.h

@@ -36,6 +36,8 @@ struct ns_lwresd {
 	dns_view_t *view;
 	ns_lwsearchlist_t *search;
 	unsigned int ndots;
+	unsigned int ntasks;
+	unsigned int nclients;
 	isc_mem_t *mctx;
 	isc_boolean_t shutting_down;
 	unsigned int refs;

bin/named/lwresd.c

@@ -60,11 +60,7 @@
 #define LWRESLISTENER_MAGIC	ISC_MAGIC('L', 'W', 'R', 'L')
 #define VALID_LWRESLISTENER(l)	ISC_MAGIC_VALID(l, LWRESLISTENER_MAGIC)
 
-/*!
- * The total number of clients we can handle will be NTASKS * NRECVS.
- */
-#define NTASKS		2	/*%< tasks to create to handle lwres queries */
-#define NRECVS		2	/*%< max clients per task */
+#define LWRESD_NCLIENTS_MAX		32768	/*%< max clients per task */
 
 typedef ISC_LIST(ns_lwreslistener_t) ns_lwreslistenerlist_t;
 
@@ -395,6 +391,24 @@ ns_lwdmanager_create(isc_mem_t *mctx, const cfg_obj_t *lwres,
 		}
 	}
 
+	obj = NULL;
+	(void)cfg_map_get(lwres, "lwres-tasks", &obj);
+	if (obj != NULL)
+		lwresd->ntasks = cfg_obj_asuint32(obj);
+	else
+		lwresd->ntasks = ns_g_cpus;
+
+	obj = NULL;
+	(void)cfg_map_get(lwres, "lwres-clients", &obj);
+	if (obj != NULL) {
+		lwresd->nclients = cfg_obj_asuint32(obj);
+		if (lwresd->nclients > LWRESD_NCLIENTS_MAX)
+			lwresd->nclients = LWRESD_NCLIENTS_MAX;
+	} else if (ns_g_lwresdonly)
+		lwresd->nclients = 1024;
+	else
+		lwresd->nclients = 256;
+
 	lwresd->magic = LWRESD_MAGIC;
 
 	*lwresdp = lwresd;
@@ -604,15 +618,24 @@ static isc_result_t
 listener_startclients(ns_lwreslistener_t *listener) {
 	ns_lwdclientmgr_t *cm;
 	unsigned int i;
-	isc_result_t result;
+	isc_result_t result = ISC_R_SUCCESS;
+
+	isc_log_write(ns_g_lctx, NS_LOGCATEGORY_GENERAL,
+		      NS_LOGMODULE_LWRESD, ISC_LOG_DEBUG(6),
+		      "listener_startclients: creating %d "
+		      "managers with %d clients each",
+		      listener->manager->ntasks, listener->manager->nclients);
 
 	/*
 	 * Create the client managers.
 	 */
-	result = ISC_R_SUCCESS;
-	for (i = 0; i < NTASKS && result == ISC_R_SUCCESS; i++)
-		result = ns_lwdclientmgr_create(listener, NRECVS,
+	for (i = 0; i < listener->manager->ntasks; i++) {
+		result = ns_lwdclientmgr_create(listener,
+						listener->manager->nclients,
 						ns_g_taskmgr);
+		if (result != ISC_R_SUCCESS)
+			break;
+	}
 
 	/*
 	 * Ensure that we have created at least one.

bin/named/named.conf.docbook

@@ -187,6 +187,8 @@ lwres {
 	view <replaceable>string</replaceable> <replaceable>optional_class</replaceable>;
 	search { <replaceable>string</replaceable>; ... };
 	ndots <replaceable>integer</replaceable>;
+	lwres-tasks <replaceable>integer</replaceable>;
+	lwres-clients <replaceable>integer</replaceable>;
 };
 </literallayout>
   </refsect1>

doc/arm/Bv9ARM-book.xml

@@ -2563,7 +2563,12 @@ $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
 	be configured to act as a lightweight resolver daemon using the
 	<command>lwres</command> statement in <filename>named.conf</filename>.
       </para>
-
+      <para>
+        The number of client queries that the <command>lwresd</command>
+        daemon is able to serve can be set using the
+        <option>lwres-tasks</option> and <option>lwres-clients</option> 
+        statements in the configuration.
+      </para>
     </sect1>
   </chapter>
 
@@ -4654,6 +4659,8 @@ badresp:1,adberr:0,findfail:0,valfail:0]
     <optional> view <replaceable>view_name</replaceable>; </optional>
     <optional> search { <replaceable>domain_name</replaceable> ; <optional> <replaceable>domain_name</replaceable> ; ... </optional> }; </optional>
     <optional> ndots <replaceable>number</replaceable>; </optional>
+    <optional> lwres-tasks <replaceable>number</replaceable>; </optional>
+    <optional> lwres-clients <replaceable>number</replaceable>; </optional>
 };
 </programlisting>
 
@@ -4711,7 +4718,32 @@ badresp:1,adberr:0,findfail:0,valfail:0]
 	  minimum
 	  number of dots in a relative domain name that should result in an
 	  exact match lookup before search path elements are appended.
-	</para>
+        </para>
+        <para>
+          The <option>lwres-tasks</option> statement specifies the number
+          of worker threads the lightweight resolver will dedicate to serving
+          clients.  By default the number is the same as the number of CPUs on
+          the system; this can be overridden using the <option>-n</option>
+          command line option when starting the server. 
+        </para>
+        <para>
+          The <option>lwres-clients</option> specifies
+          the number of client objects per thread the lightweight
+          resolver should create to serve client queries.
+          By default, if the lightweight resolver runs as a part
+          of <command>named</command>, 256 client objects are
+          created for each task; if it runs as <command>lwresd</command>,
+          1024 client objects are created for each thread. The maximum
+          value is 32768; higher values will be silently ignored and
+          the maximum will be used instead.
+          Note that setting too high a value may overconsume
+          system resources.
+        </para>
+        <para>
+          The maximum number of client queries that the lightweight
+          resolver can handle at any one time equals
+          <option>lwres-tasks</option> times <option>lwres-clients</option>.
+        </para>
       </sect2>
       <sect2>
 	<title><command>masters</command> Statement Grammar</title>

lib/isccfg/namedconf.c

@@ -2925,6 +2925,8 @@ lwres_clauses[] = {
 	{ "view", &cfg_type_lwres_view, 0 },
 	{ "search", &cfg_type_lwres_searchlist, 0 },
 	{ "ndots", &cfg_type_uint32, 0 },
+	{ "lwres-tasks", &cfg_type_uint32, 0},
+	{ "lwres-clients", &cfg_type_uint32, 0},
 	{ NULL, NULL, 0 }
 };