[master] 5b79a6580 Diffentiate "no backend" from "none resolved" in VDI_Resolve()

[Nils Goroll]

commit 5b79a65807d63668dd00f0bca9151dd9651d6271
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed May 13 18:16:59 2020 +0200

    Diffentiate "no backend" from "none resolved" in VDI_Resolve()
    
    recover a minor improvement from #2680:
    
    This commit is to emit slightly different error messages to
    differentiate between the cases "no backend set in vcl" and
    "none returned from the director".
    
    Includes minor polishing
    
    Ref #2860 #3311

diff --git a/bin/varnishd/cache/cache_director.c b/bin/varnishd/cache/cache_director.c
index 3e6902031..1aa4388d5 100644
--- a/bin/varnishd/cache/cache_director.c
+++ b/bin/varnishd/cache/cache_director.c
@@ -103,24 +103,26 @@ VRT_VDI_Resolve(VRT_CTX, VCL_BACKEND d)
 static VCL_BACKEND
 VDI_Resolve(VRT_CTX)
 {
-	const struct director *d;
+	VCL_BACKEND d;
 	struct busyobj *bo;
 
+	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	bo = ctx->bo;
 	CHECK_OBJ_NOTNULL(bo, BUSYOBJ_MAGIC);
-	CHECK_OBJ_ORNULL(bo->director_req, DIRECTOR_MAGIC);
-	d = VRT_VDI_Resolve(ctx, bo->director_req);
-	CHECK_OBJ_ORNULL(d, DIRECTOR_MAGIC);
-	if (d == NULL) {
-		VSLb(bo->vsl, SLT_FetchError, "No backend");
-	} else {
-		AN(d->vdir);
 
-		if (d->vdir->admin_health->health == 0)
-			d = NULL;
+	if (bo->director_req == NULL) {
+		VSLb(bo->vsl, SLT_FetchError, "No backend");
+		return (NULL);
 	}
 
-	return (d);
+	CHECK_OBJ(bo->director_req, DIRECTOR_MAGIC);
+	d = VRT_VDI_Resolve(ctx, bo->director_req);
+	if (d != NULL)
+		return (d);
+
+	VSLb(bo->vsl, SLT_FetchError,
+	    "Director %s returned no backend", bo->director_req->vcl_name);
+	return (NULL);
 }
 
 /* Get a set of response headers -------------------------------------*/