lib/nsrep: some changes in NS selection algorithm

diff --git a/lib/nsrep.c b/lib/nsrep.c
index 30101a3db61234fb9baaf4df92060336558609a4..c751aec341d756a6672a3b2154bccd4e3cacde03 100644 (file)
--- a/lib/nsrep.c
+++ b/lib/nsrep.c
@@ -161,21 +161,27 @@ static int eval_nsrep(const char *k, void *v, void *baton)
        /* Probabilistic bee foraging strategy (naive).
         * The fastest NS is preferred by workers until it is depleted (timeouts or degrades),
         * at the same time long distance scouts probe other sources (low probability).
-        * Servers on TIMEOUT (depleted) can be probed by the dice roll only */
-       if (score <= ns->score && (score < KR_NS_LONG  || (qry->flags.NO_THROTTLE && (score < KR_NS_TIMEOUT)))) {
+        * Servers on TIMEOUT will not have probed at all.
+        * Servers with score above KR_NS_LONG will have periodically removed from
+        * reputation cache, so that kresd can reprobe them. */
+       if (score >= KR_NS_TIMEOUT) {
+               return kr_ok();
+       } else if (score <= ns->score &&
+                  (score < KR_NS_LONG  || qry->flags.NO_THROTTLE)) {
+               update_nsrep_set(ns, (const knot_dname_t *)k, addr_choice, score);
+               ns->reputation = reputation;
+       } else if ((kr_rand_uint(100) < 10) &&
+                  (kr_rand_uint(KR_NS_MAX_SCORE) >= score)) {
+               /* With 10% chance probe server with a probability
+                * given by its RTT / MAX_RTT. */
+               update_nsrep_set(ns, (const knot_dname_t *)k, addr_choice, score);
+               ns->reputation = reputation;
+               return 1; /* Stop evaluation */
+       } else if (ns->score > KR_NS_MAX_SCORE) {
+               /* Check if any server was already selected.
+                * If no, pick current server and continue evaluation. */
                update_nsrep_set(ns, (const knot_dname_t *)k, addr_choice, score);
                ns->reputation = reputation;
-       } else if (score < KR_NS_TIMEOUT) {
-               /* With 10% chance, probe server with a probability given by its RTT / MAX_RTT */
-               if ((kr_rand_uint(100) < 10) && (kr_rand_uint(KR_NS_MAX_SCORE) >= score)) {
-                       /* If this is a low-reliability probe, go with TCP to get ICMP reachability check. */
-                       if (score >= KR_NS_LONG) {
-                               qry->flags.TCP = true;
-                       }
-                       update_nsrep_set(ns, (const knot_dname_t *)k, addr_choice, score);
-                       ns->reputation = reputation;
-                       return 1; /* Stop evaluation */
-               }
        }
 
        return kr_ok();
@@ -240,7 +246,13 @@ int kr_nsrep_elect(struct kr_query *qry, struct kr_context *ctx)
 
        struct kr_nsrep *ns = &qry->ns;
        ELECT_INIT(ns, ctx);
-       return map_walk(&qry->zone_cut.nsset, eval_nsrep, qry);
+       int ret = map_walk(&qry->zone_cut.nsset, eval_nsrep, qry);
+       if (qry->ns.score <= KR_NS_MAX_SCORE && qry->ns.score >= KR_NS_LONG) {
+               /* This is a low-reliability probe,
+                * go with TCP to get ICMP reachability check. */
+               qry->flags.TCP = true;
+       }
+       return ret;
 }
 
 int kr_nsrep_elect_addr(struct kr_query *qry, struct kr_context *ctx)