Merge branch 'ondrej-offload-statschannel' into 'main'

Offload the isc_http response processing to worker thread

Closes #4680

See merge request isc-projects/bind9!7647

CHANGES

@@ -1,3 +1,6 @@
+6373.	[func]		Offload the isc_http response processing to worker
+			thread. [GL #4680]
+
 6372.	[func]		Implement signature jitter for dnssec-policy. [GL #4554]
 
 6371.	[bug]		Access to the trust bytes in the ncache data needed to

doc/notes/notes-current.rst

@@ -33,7 +33,8 @@ Removed Features
 Feature Changes
 ~~~~~~~~~~~~~~~
 
-- None.
+- Querying the statistics channel no longer blocks the DNS communication
+  on the networking event loop. :gl:`#4680`
 
 Bug Fixes
 ~~~~~~~~~

lib/isc/httpd.c

@@ -598,6 +598,12 @@ isc__httpd_sendreq_new(isc_httpd_t *httpd) {
 
 	isc_buffer_initnull(&req->bodybuffer);
 
+	/*
+	 * We don't need to attach to httpd here because it gets only cleaned
+	 * when the last handle has been detached
+	 */
+	req->httpd = httpd;
+
 	return (req);
 }
 
@@ -749,10 +755,11 @@ httpd_compress(isc_httpd_sendreq_t *req) {
 #endif /* ifdef HAVE_ZLIB */
 
 static void
-prepare_response(isc_httpdmgr_t *mgr, isc_httpd_t *httpd,
-		 isc_httpd_sendreq_t **reqp) {
-	isc_httpd_sendreq_t *req = NULL;
-	isc_time_t now;
+prepare_response(void *arg) {
+	isc_httpd_sendreq_t *req = arg;
+	isc_httpd_t *httpd = req->httpd;
+	isc_httpdmgr_t *mgr = httpd->mgr;
+	isc_time_t now = isc_time_now();
 	char datebuf[ISC_FORMATHTTPTIMESTAMP_SIZE];
 	const char *path = "/";
 	size_t path_len = 1;
@@ -761,9 +768,8 @@ prepare_response(isc_httpdmgr_t *mgr, isc_httpd_t *httpd,
 	isc_result_t result;
 
 	REQUIRE(VALID_HTTPD(httpd));
-	REQUIRE(reqp != NULL && *reqp == NULL);
+	REQUIRE(req != NULL);
 
-	now = isc_time_now();
 	isc_time_formathttptimestamp(&now, datebuf, sizeof(datebuf));
 
 	if (httpd->up.field_set & (1 << ISC_UF_PATH)) {
@@ -779,8 +785,6 @@ prepare_response(isc_httpdmgr_t *mgr, isc_httpd_t *httpd,
 	}
 	UNLOCK(&mgr->lock);
 
-	req = isc__httpd_sendreq_new(httpd);
-
 	if (url == NULL) {
 		result = mgr->render_404(httpd, NULL, NULL, &req->retcode,
 					 &req->retmsg, &req->mimetype,
@@ -874,14 +878,20 @@ prepare_response(isc_httpdmgr_t *mgr, isc_httpd_t *httpd,
 	}
 	httpd->recvlen -= httpd->consume;
 	httpd->consume = 0;
+}
+
+static void
+prepare_response_done(void *arg) {
+	isc_region_t r;
+	isc_httpd_sendreq_t *req = arg;
+	isc_httpd_t *httpd = req->httpd;
 
 	/*
-	 * We don't need to attach to httpd here because it gets only cleaned
-	 * when the last handle has been detached
+	 * Determine total response size.
 	 */
-	req->httpd = httpd;
+	isc_buffer_usedregion(req->sendbuffer, &r);
 
-	*reqp = req;
+	isc_nm_send(httpd->handle, &r, httpd_senddone, req);
 }
 
 static void
@@ -889,8 +899,6 @@ httpd_request(isc_nmhandle_t *handle, isc_result_t eresult,
 	      isc_region_t *region, void *arg) {
 	isc_httpd_t *httpd = arg;
 	isc_httpdmgr_t *mgr = httpd->mgr;
-	isc_httpd_sendreq_t *req = NULL;
-	isc_region_t r;
 	size_t last_len = 0;
 	isc_result_t result;
 
@@ -941,15 +949,10 @@ httpd_request(isc_nmhandle_t *handle, isc_result_t eresult,
 		goto close_readhandle;
 	}
 
-	prepare_response(mgr, httpd, &req);
-
-	/*
-	 * Determine total response size.
-	 */
-	isc_buffer_usedregion(req->sendbuffer, &r);
-
+	isc_httpd_sendreq_t *req = isc__httpd_sendreq_new(httpd);
 	isc_nmhandle_ref(handle);
-	isc_nm_send(handle, &r, httpd_senddone, req);
+	isc_work_enqueue(isc_loop(), prepare_response, prepare_response_done,
+			 req);
 	return;
 
 close_readhandle:

lib/isc/xml.c

@@ -53,9 +53,8 @@ isc__xml_initialize(void) {
 	isc_mem_setname(isc__xml_mctx, "libxml2");
 	isc_mem_setdestroycheck(isc__xml_mctx, false);
 
-	RUNTIME_CHECK(xmlGcMemSetup(isc__xml_free, isc__xml_malloc,
-				    isc__xml_malloc, isc__xml_realloc,
-				    isc__xml_strdup) == 0);
+	RUNTIME_CHECK(xmlMemSetup(isc__xml_free, isc__xml_malloc,
+				  isc__xml_realloc, isc__xml_strdup) == 0);
 
 	xmlInitParser();
 #endif /* HAVE_LIBXML2 */

suppr-lsan.txt

@@ -24,3 +24,4 @@ leak:pkcs11_enumerate_slots
 leak:pkcs11_getattr_alloc
 leak:pkcs11_init_key
 leak:pkcs11_strdup
+leak:xmlGetGlobalState