Add the element enum to .backend().

README.rst

@@ -720,13 +720,14 @@ Example::
 
 .. _xset.backend():
 
-BACKEND xset.backend(INT n, ENUM select)
-----------------------------------------
+BACKEND xset.backend(INT n, STRING element, ENUM select)
+--------------------------------------------------------
 
 ::
 
       BACKEND xset.backend(
             INT n=0,
+            STRING element=0,
             ENUM {UNIQUE, EXACT, FIRST, LAST, SHORTEST, LONGEST} select=UNIQUE
       )
 

src/tests/backend.vtc

@@ -48,6 +48,17 @@ varnish v1 -vcl {
 			set resp.http.Backend-Longest
 			    = s.backend(select=LONGEST);
 		}
+
+		set resp.http.Foo = s.backend(element="foo");
+		set resp.http.Bar = s.backend(element="bar");
+		set resp.http.Baz = s.backend(element="baz");
+		set resp.http.Quux = s.backend(element="quux");
+		set resp.http.Foobar = s.backend(element="foobar");
+		if (req.http.Element) {
+			set resp.http.Element
+				= s.backend(element=req.http.Element);
+		}
+
 		return (deliver);
 	}
 } -start
@@ -62,6 +73,12 @@ client c1 {
 	expect resp.http.N-4 == "b4"
 	expect resp.http.N-5 == "b5"
 
+	expect resp.http.Foo == "b1"
+	expect resp.http.Bar == "b2"
+	expect resp.http.Baz == "b3"
+	expect resp.http.Quux == "b4"
+	expect resp.http.Foobar == "b5"
+
 	txreq -hdr "Word: foo"
 	rxresp
 	expect resp.status == 200
@@ -128,6 +145,11 @@ client c1 {
 	expect_close
 } -run
 
+client c1 {
+	txreq -hdr "Element: oof"
+	expect_close
+} -run
+
 logexpect l1 -v v1 -d 1 -g vxid -q "VCL_Error" {
 	expect 0 * Begin req
 	expect * = VCL_Error {^vmod selector failure: s\.backend\(\) called without prior match$}
@@ -138,6 +160,11 @@ logexpect l1 -v v1 -d 1 -g vxid -q "VCL_Error" {
 	expect * = VCL_Error {^vmod selector failure: s\.backend\(6\): set has 5 elements$}
 	expect * = VCL_return fail
 	expect * = End
+
+	expect 0 * Begin req
+	expect * = VCL_Error {^vmod selector failure: s\.backend\(element="oof"\): no such element$}
+	expect * = VCL_return fail
+	expect * = End
 } -run
 
 varnish v1 -vcl {
@@ -185,6 +212,18 @@ varnish v1 -vcl {
 			set resp.http.Backend-Longest
 			    = s.backend(select=LONGEST);
 		}
+		if (req.http.Element) {
+			set resp.http.Element
+				= s.backend(element=req.http.Element);
+			set resp.http.Element-Unique = s.backend(select=UNIQUE);
+			set resp.http.Element-Exact = s.backend(select=EXACT);
+			set resp.http.Element-First = s.backend(select=FIRST);
+			set resp.http.Element-Last = s.backend(select=LAST);
+			set resp.http.Element-Shortest
+				= s.backend(select=SHORTEST);
+			set resp.http.Element-Longest
+				= s.backend(select=LONGEST);
+		}
 		return (deliver);
 	}
 }
@@ -244,6 +283,17 @@ client c1 {
 	expect resp.http.Backend-Last == "b4"
 	expect resp.http.Backend-Shortest == "b4"
 	expect resp.http.Backend-Longest == "b3"
+
+	txreq -hdr "Element: foo"
+	rxresp
+	expect resp.status == 200
+	expect resp.http.Element == "b4"
+	expect resp.http.Element-Unique == "b4"
+	expect resp.http.Element-Exact == "b4"
+	expect resp.http.Element-First == "b4"
+	expect resp.http.Element-Last == "b4"
+	expect resp.http.Element-Shortest == "b4"
+	expect resp.http.Element-Longest == "b4"
 } -run
 
 logexpect l1 -v v1 -d 0 -g vxid -q "VCL_Error" {

src/vmod_selector.c

@@ -696,7 +696,8 @@ vmod_set_which(VRT_CTX, struct vmod_selector_set *set, VCL_ENUM selects)
 
 static unsigned
 get_idx(VRT_CTX, VCL_INT n, const struct vmod_selector_set * const restrict set,
-	const char * const restrict method, VCL_ENUM const restrict selects)
+	const char * const restrict method, VCL_STRING const restrict element,
+	VCL_ENUM const restrict selects)
 {
 	struct match_data *match;
 
@@ -708,6 +709,12 @@ get_idx(VRT_CTX, VCL_INT n, const struct vmod_selector_set * const restrict set,
 		}
 		return (n - 1);
 	}
+	if (element != NULL)
+		if (!vmod_set_match(ctx, TRUST_ME(set), element)) {
+			VFAIL(ctx, "%s.%s(element=\"%s\"): no such element",
+			      set->vcl_name, method, element);
+			return (UINT_MAX);
+		}
 
 	match = get_existing_match_data(ctx, set, method);
 	if (match == NULL || match->n == 0)
@@ -724,7 +731,7 @@ vmod_set_element(VRT_CTX, struct vmod_selector_set *set, VCL_INT n,
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(set, VMOD_SELECTOR_SET_MAGIC);
 
-	idx = get_idx(ctx, n, set, "element", selects);
+	idx = get_idx(ctx, n, set, "element", NULL, selects);
 	if (idx == UINT_MAX)
 		return (NULL);
 	return (set->members[idx]);
@@ -746,7 +753,7 @@ check_added(VRT_CTX, const struct vmod_selector_set * const restrict set,
 
 VCL_BACKEND
 vmod_set_backend(VRT_CTX, struct vmod_selector_set *set, VCL_INT n,
-		 VCL_ENUM selects)
+		 VCL_STRING element, VCL_ENUM selects)
 {
 	unsigned idx;
 	VCL_BACKEND b;
@@ -754,7 +761,7 @@ vmod_set_backend(VRT_CTX, struct vmod_selector_set *set, VCL_INT n,
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(set, VMOD_SELECTOR_SET_MAGIC);
 
-	idx = get_idx(ctx, n, set, "backend", selects);
+	idx = get_idx(ctx, n, set, "backend", element, selects);
 	if (idx == UINT_MAX)
 		return (NULL);
 	if (!check_added(ctx, set, idx, BACKEND, "backend", "backend"))
@@ -775,7 +782,7 @@ vmod_set_string(VRT_CTX, struct vmod_selector_set * set, VCL_INT n,
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(set, VMOD_SELECTOR_SET_MAGIC);
 
-	idx = get_idx(ctx, n, set, "string", selects);
+	idx = get_idx(ctx, n, set, "string", NULL, selects);
 	if (idx == UINT_MAX)
 		return (NULL);
 	if (!check_added(ctx, set, idx, STRING, "string", "string"))
@@ -795,7 +802,7 @@ vmod_set_integer(VRT_CTX, struct vmod_selector_set * set, VCL_INT n,
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(set, VMOD_SELECTOR_SET_MAGIC);
 
-	idx = get_idx(ctx, n, set, "integer", selects);
+	idx = get_idx(ctx, n, set, "integer", NULL, selects);
 	if (idx == UINT_MAX)
 		return (0);
 	if (!check_added(ctx, set, idx, INTEGER, "integer", "integer"))
@@ -815,7 +822,7 @@ get_re(VRT_CTX, const struct vmod_selector_set * const restrict set,
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(set, VMOD_SELECTOR_SET_MAGIC);
 
-	idx = get_idx(ctx, n, set, method, selects);
+	idx = get_idx(ctx, n, set, method, NULL, selects);
 	if (idx == UINT_MAX)
 		return (NULL);
 	if (!check_added(ctx, set, idx, REGEX, method, "regex"))

src/vmod_selector.vcc

@@ -653,7 +653,7 @@ Example::
      set resp.http.Location = "http://other.com" + myset.element();
   }
 
-$Method BACKEND .backend(INT n=0,
+$Method BACKEND .backend(INT n=0, STRING element=0,
 			 ENUM {UNIQUE, EXACT, FIRST, LAST, SHORTEST, LONGEST}
 			 select=UNIQUE)