lib/nsrep: lower bound on rtt, optional throttling

when a NS is in the TIMEOUT, it can’t be autoselected by default but only probed after a successful dice roll - however in some scenarios we’d like to probe timeouting servers more thoroughly

diff --git a/lib/nsrep.c b/lib/nsrep.c
index 9e7e990905882b241acc7283e00ac7c9ff1fa889..967c5c89bdb7eef371f73abbe507eb71dae8c2ae 100644 (file)
--- a/lib/nsrep.c
+++ b/lib/nsrep.c
@@ -21,6 +21,7 @@
 #include <libknot/internal/sockaddr.h>
 
 #include "lib/nsrep.h"
+#include "lib/rplan.h"
 #include "lib/defines.h"
 #include "lib/generic/pack.h"
 
@@ -97,7 +98,7 @@ static int eval_nsrep(const char *k, void *v, void *baton)
         * 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_TIMEOUT) {
+       if (score < ns->score && (ns->flags & QUERY_NO_THROTTLE || score < KR_NS_TIMEOUT)) {
                update_nsrep(ns, (const knot_dname_t *)k, addr, score);
        } else {
                /* With 5% chance, probe server with a probability given by its RTT / MAX_RTT */
@@ -135,6 +136,9 @@ int kr_nsrep_update(struct kr_nsrep *ns, unsigned score, kr_nsrep_lru_t *repcach
        if (score > KR_NS_MAX_SCORE) {
                score = KR_NS_MAX_SCORE;
        }
+       if (score <= KR_NS_UNKNOWN) {
+               score = KR_NS_UNKNOWN + 1;
+       }
        /* Set initial value or smooth over last two measurements */
        if (*cur != 0) {
                *cur = (*cur + score) / 2;

diff --git a/lib/nsrep.h b/lib/nsrep.h
index 4d2ad8a4bce9af53a829d65844c74e56be73914e..7df5493d08d778c13a0867860fbf292782f7e4be 100644 (file)
--- a/lib/nsrep.h
+++ b/lib/nsrep.h
@@ -46,6 +46,7 @@ typedef lru_hash(unsigned) kr_nsrep_lru_t;
 struct kr_nsrep
 {
        unsigned score;                  /**< Server score */
+       unsigned flags;                  /**< Server flags */
        const knot_dname_t *name;        /**< Server name */
        kr_nsrep_lru_t *repcache;        /**< Reputation cache pointer */
        union {

diff --git a/lib/resolve.c b/lib/resolve.c
index 9adb019ff713cd7f1d9836008d945168ef2af6b3..e447b9a5d7229d224ae577ea4d480c2291dbe854 100644 (file)
--- a/lib/resolve.c
+++ b/lib/resolve.c
@@ -431,6 +431,11 @@ int kr_resolve_produce(struct kr_request *request, struct sockaddr **dst, int *t
 ns_election:
        /* Elect best nameserver candidate */
        assert(++ns_election_iter < KR_ITER_LIMIT);
+       /* Set slow NS throttling mode */
+       qry->ns.flags = 0;
+       if (qry->flags & QUERY_NO_THROTTLE) {
+               qry->ns.flags = QUERY_NO_THROTTLE;
+       }
        kr_nsrep_elect(&qry->ns, &qry->zone_cut.nsset, request->ctx->nsrep);
        if (qry->ns.score > KR_NS_MAX_SCORE) {
                DEBUG_MSG("=> no valid NS left\n");

diff --git a/lib/rplan.h b/lib/rplan.h
index e5afd9bbae7aacdf507d62d2e7748ee2e70b78e6..f47bd28ce47acc491fa473abdac113c183397216 100644 (file)
--- a/lib/rplan.h
+++ b/lib/rplan.h
@@ -29,13 +29,14 @@
 /** Query flags */
 enum kr_query_flag {
        QUERY_NO_MINIMIZE = 1 << 0, /**< Don't minimize QNAME. */
-       QUERY_TCP         = 1 << 1, /**< Use TCP for this query. */
-       QUERY_RESOLVED    = 1 << 2, /**< Query is resolved. */
-       QUERY_AWAIT_IPV4  = 1 << 3, /**< Query is waiting for A address. */
-       QUERY_AWAIT_IPV6  = 1 << 4, /**< Query is waiting for AAAA address. */
-       QUERY_AWAIT_CUT   = 1 << 5, /**< Query is waiting for zone cut lookup */
-       QUERY_SAFEMODE    = 1 << 6, /**< Don't use fancy stuff (EDNS...) */
-       QUERY_CACHED      = 1 << 7  /**< Query response is cached. */
+       QUERY_NO_THROTTLE = 1 << 1, /**< No query/slow NS throttling. */
+       QUERY_TCP         = 1 << 2, /**< Use TCP for this query. */
+       QUERY_RESOLVED    = 1 << 3, /**< Query is resolved. */
+       QUERY_AWAIT_IPV4  = 1 << 4, /**< Query is waiting for A address. */
+       QUERY_AWAIT_IPV6  = 1 << 5, /**< Query is waiting for AAAA address. */
+       QUERY_AWAIT_CUT   = 1 << 6, /**< Query is waiting for zone cut lookup */
+       QUERY_SAFEMODE    = 1 << 7, /**< Don't use fancy stuff (EDNS...) */
+       QUERY_CACHED      = 1 << 8  /**< Query response is cached. */
 };
 
 /**