Add the stats PESI.esidata_activate and .esidata_vdp.

These should *always* match. If not, then there is indeed a race
with respect to the attribute's value at activate() and VDP init times.

src/pesi.vsc

@@ -12,4 +12,16 @@
 
 	Number of times no threads were available for parallel ESI.
 
+.. varnish_vsc:: esidata_activate
+	:type:  counter
+	:oneliner:      Object attribute ESIDATA set in activate()
+
+	Number of times the ESIDATA attribute was true on actvate() calls
+
+.. varnish_vsc:: esidata_vdp
+	:type:  counter
+	:oneliner:      Object attribute ESIDATA set in VDP init
+
+	Number of times the ESIDATA attribute was true at VDP init time
+
 .. varnish_vsc_end::    pesi

src/tests/e00003.vtc

@@ -101,6 +101,8 @@ client c1 {
 client c1 -run
 varnish v1 -expect esi_errors == 0
 varnish v1 -expect MAIN.s_resp_bodybytes == 150
+varnish v1 -expect PESI.esidata_activate > 0
+varnish v1 -expect PESI.esidata_vdp > 0
 delay 1
 
 logexpect l1 -v v1 -d 1 -g vxid -q "vxid == 1001" {

src/vdp_pesi.c

@@ -52,6 +52,7 @@
 
 #include "debug.h"
 #include "vdp_pesi.h"
+#include "VSC_pesi.h"
 #include "node.h"
 #include "node_assert.h"
 #include "pesi.h"
@@ -60,6 +61,9 @@
 
 #include "misc.h"
 
+/* in pesi.c */
+extern struct VSC_pesi *stats;
+
 /*lint -esym(843, block_final, front_push)
  * we want to keep the option to tune these at runtime in a debugger
  */
@@ -659,10 +663,14 @@ vdp_pesi_init(struct vdp_ctx *vdc, void **priv, struct objcore *oc)
 	struct pecx *pecx;
 	struct pesi_tree *pesi_tree;
 	struct node *root_node;
+	int activated;
 
 	CHECK_OBJ_NOTNULL(vdc, VDP_CTX_MAGIC);
 	CHECK_OBJ_ORNULL(oc, OBJCORE_MAGIC);
-	if (oc == NULL || !ObjHasAttr(vdc->wrk, oc, OA_ESIDATA))
+	activated = (oc != NULL && ObjHasAttr(vdc->wrk, oc, OA_ESIDATA));
+	if (activated)
+		stats->esidata_vdp++;
+	else
 		return (1);
 
 	req = vdc->req;

src/vmod_pesi.c

@@ -221,6 +221,9 @@ pesi_resp_default_filter_list(void *arg, struct vsb *vsb)
 		ObjHasAttr(req->wrk, req->objcore, OA_ESIDATA) */)
 		VSB_cat(vsb, " pesi");
 
+	if (ObjHasAttr(req->wrk, req->objcore, OA_ESIDATA))
+		stats->esidata_activate++;
+
 	if (cache_param->http_gzip_support &&
 	    ObjCheckFlag(req->wrk, req->objcore, OF_GZIPED) &&
 	    !RFC2616_Req_Gzip(req->http))