Ditch the director cooling list and trust the refcounts.

(4th part of #3599)

bin/varnishd/cache/cache_backend.c

@@ -54,9 +54,6 @@
 
 static const char * const vbe_proto_ident = "HTTP Backend";
 
-static VTAILQ_HEAD(, backend) backends = VTAILQ_HEAD_INITIALIZER(backends);
-static VTAILQ_HEAD(, backend) cool_backends =
-    VTAILQ_HEAD_INITIALIZER(cool_backends);
 static struct lock backends_mtx;
 
 /*--------------------------------------------------------------------*/
@@ -426,13 +423,9 @@ vbe_free(struct backend *be)
 
 	VSC_vbe_Destroy(&be->vsc_seg);
 	Lck_Lock(&backends_mtx);
-	if (be->cooled > 0)
-		VTAILQ_REMOVE(&cool_backends, be, list);
-	else
-		VTAILQ_REMOVE(&backends, be, list);
 	VSC_C_main->n_backend--;
-	VCP_Rel(&be->conn_pool);
 	Lck_Unlock(&backends_mtx);
+	VCP_Rel(&be->conn_pool);
 
 #define DA(x)	do { if (be->x != NULL) free(be->x); } while (0)
 #define DN(x)	/**/
@@ -630,21 +623,19 @@ VRT_new_backend_clustered(VRT_CTX, struct vsmw_cluster *vc,
 	}
 
 	Lck_Lock(&backends_mtx);
-	VTAILQ_INSERT_TAIL(&backends, be, list);
 	VSC_C_main->n_backend++;
 	Lck_Unlock(&backends_mtx);
 
 	be->director = VRT_AddDirector(ctx, m, be, "%s", vrt->vcl_name);
 
-	if (be->director != NULL) {
-		/* for cold VCL, update initial director state */
-		if (be->probe != NULL && ! vcl->temp->is_warm)
-			VBP_Update_Backend(be->probe);
-		return (be->director);
+	if (be->director == NULL) {
+		vbe_free(be);
+		return (NULL);
 	}
-
-	vbe_free(be);
-	return (NULL);
+	/* for cold VCL, update initial director state */
+	if (be->probe != NULL)
+		VBP_Update_Backend(be->probe);
+	return (be->director);
 }
 
 VCL_BACKEND
@@ -664,47 +655,11 @@ VRT_new_backend(VRT_CTX, const struct vrt_backend *vrt)
 void
 VRT_delete_backend(VRT_CTX, VCL_BACKEND *dp)
 {
-	VCL_BACKEND d;
-	struct backend *be;
-
-	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
-	TAKE_OBJ_NOTNULL(d, dp, DIRECTOR_MAGIC);
-	CAST_OBJ_NOTNULL(be, d->priv, BACKEND_MAGIC);
-	Lck_Lock(be->director->mtx);
-	VRT_DisableDirector(be->director);
-	Lck_Unlock(be->director->mtx);
-	Lck_Lock(&backends_mtx);
-	AZ(be->cooled);
-	be->cooled = VTIM_real() + 60.;
-	VTAILQ_REMOVE(&backends, be, list);
-	VTAILQ_INSERT_TAIL(&cool_backends, be, list);
-	Lck_Unlock(&backends_mtx);
 
-	// NB. The backend is still usable for the ongoing transactions,
-	// this is why we don't bust the director's magic number.
-}
-
-/*---------------------------------------------------------------------*/
-
-void
-VBE_Poll(void)
-{
-	struct backend *be, *be2;
-	vtim_real now = VTIM_real();
-
-	ASSERT_CLI();
-	Lck_Lock(&backends_mtx);
-	VTAILQ_FOREACH_SAFE(be, &cool_backends, list, be2) {
-		CHECK_OBJ_NOTNULL(be, BACKEND_MAGIC);
-		if (be->cooled > now)
-			break;
-		if (be->n_conn > 0)
-			continue;
-		Lck_Unlock(&backends_mtx);
-		VRT_DelDirector(&be->director);
-		Lck_Lock(&backends_mtx);
-	}
-	Lck_Unlock(&backends_mtx);
+	(void)ctx;
+	CHECK_OBJ_NOTNULL(*dp, DIRECTOR_MAGIC);
+	VRT_DisableDirector(*dp);
+	VRT_Assign_Backend(dp, NULL);
 }
 
 /*---------------------------------------------------------------------*/

bin/varnishd/cache/cache_backend.h

@@ -54,8 +54,6 @@ struct backend {
 
 	unsigned		n_conn;
 
-	VTAILQ_ENTRY(backend)	list;
-
 	struct vrt_endpoint	*endpoint;
 
 	VRT_BACKEND_FIELDS()
@@ -71,8 +69,6 @@ struct backend {
 	struct conn_pool	*conn_pool;
 
 	VCL_BACKEND		director;
-
-	vtim_real		cooled;
 };
 
 /*---------------------------------------------------------------------

bin/varnishd/cache/cache_cli.c

@@ -77,7 +77,6 @@ cli_cb_before(const struct cli *cli)
 	ASSERT_CLI();
 	VSL(SLT_CLI, 0, "Rd %s", VSB_data(cli->cmd));
 	VCL_Poll();
-	VBE_Poll();
 	Lck_Lock(&cli_mtx);
 }
 

bin/varnishd/cache/cache_req.c

@@ -256,7 +256,7 @@ Req_Cleanup(struct sess *sp, struct worker *wrk, struct req *req)
 	if (IS_TOPREQ(req))
 		AZ(req->top->vcl0);
 
-	req->director_hint = NULL;
+	AZ(req->director_hint);
 	req->restarts = 0;
 
 	if (req->vcl != NULL)

bin/varnishd/cache/cache_varnishd.h

@@ -162,7 +162,6 @@ void VCA_Shutdown(void);
 
 /* cache_backend_cfg.c */
 void VBE_InitCfg(void);
-void VBE_Poll(void);
 
 void VBP_Init(void);
 

bin/varnishd/cache/cache_vcl.h

@@ -71,7 +71,6 @@ extern struct lock		vcl_mtx;
 extern struct vcl		*vcl_active; /* protected by vcl_mtx */
 struct vcl *vcl_find(const char *);
 void VCL_Update(struct vcl **, struct vcl *);
-void vcldir_free(struct vcldir *);
 
 struct vcltemp {
 	const char * const	name;

bin/varnishd/cache/cache_vrt_vcl.c

@@ -140,7 +140,7 @@ VCL_Rel(struct vcl **vcc)
 
 /*--------------------------------------------------------------------*/
 
-void
+static void
 vcldir_free(struct vcldir *vdir)
 {