better approximation of change time

src/vmod_all_healthy.c

@@ -36,6 +36,7 @@
 #include <cache/cache_director.h>
 #include <vcl.h>
 #include <vrt.h>
+#include <vtim.h>
 
 #include "vcc_all_healthy_if.h"
 
@@ -220,25 +221,53 @@ static VCL_BACKEND vmod_director_resolve(VCL_BACKEND b, struct worker *w,
 	return (d->backend);
 }
 
+/*
+ * we can only approximate the change time for the unhealthy case because we do
+ * not have the full record: consider all backends healthy, a goes down, then b,
+ * a comes back up: we would need to record the time a went down initially. We
+ * approximate by returning the time b went down, so:
+ *
+ * - unhealthy: earliest change of unhealthy backend
+ * - healthy: latest change of healthy backend
+ */
+
 static VCL_BOOL
 vmod_director_healthy(VCL_BACKEND b, const struct busyobj *bo,
 VCL_TIME *t)
 {
 	struct vmod_all_healthy_director *d;
 	int i;
-	VCL_BOOL r = 1;
-	VCL_TIME bt;
+	VCL_BOOL br, r = 1;
+	VCL_TIME bt, tt[2];
 	VCL_BACKEND be;
 
 	CAST_OBJ_NOTNULL(d, b->priv, VMOD_ALL_HEALTHY_DIRECTOR_MAGIC);
 
+	if (t) {
+		tt[0] = VTIM_real();
+		tt[1] = 0.0;
+	}
+
 	for (i = 0; i < d->nconsider; i++) {
 		be = d->consider[i];
 		CHECK_OBJ_NOTNULL(be, DIRECTOR_MAGIC);
-		r &= be->healthy(be, bo, &bt);
-		if (t && bt > *t)
-			*t = bt;
+		br = !!be->healthy(be, bo, &bt);
+		r &= br;
+
+		if (t) {
+			if (r && br) {
+				if (bt > tt[1])
+					tt[1] = bt;
+			} else if (! br) {
+				if (bt < tt[0])
+					tt[0] = bt;
+			}
+		}
 	}
 
+	assert(r == 0 || r == 1);
+	if (t)
+		*t = tt[r];
+
 	return (r);
 }