From: Marek Vavrusa <marek@vavrusa.com>
Date: Mon, 18 Apr 2016 00:32:17 +0000 (-0700)
Subject: engine: clear bad scorers from RTT every 5 minutes
X-Git-Tag: v1.0.0~29
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b64d6ce7a09bd19d56a41759eba9260d6f960908;p=thirdparty%2Fknot-resolver.git

engine: clear bad scorers from RTT every 5 minutes

an internal timer walks RTT timer periodically and
clears entries with bad results every 5 minutes.
this means that a timeouted entry penalty is
capped to that interval, making sure that the
bad reputation doesn't last forever
---

diff --git a/daemon/engine.c b/daemon/engine.c
index 1f3bbed25..4c0e0c50c 100644
--- a/daemon/engine.c
+++ b/daemon/engine.c
@@ -41,6 +41,9 @@
 /** @internal Annotate for static checkers. */
 KR_NORETURN int lua_error (lua_State *L);
 
+/* Cleanup engine state every 5 minutes */
+const size_t CLEANUP_TIMER = 5*60*1000;
+
 /*
  * Global bindings.
  */
@@ -455,6 +458,22 @@ static int init_state(struct engine *engine)
 	return kr_ok();
 }
 
+static void update_state(uv_timer_t *handle)
+{
+	struct engine *engine = handle->data;
+
+	/* Walk RTT table, clearing all entries with bad score
+	 * to compensate for intermittent network issues or temporary bad behaviour. */
+	kr_nsrep_lru_t *table = engine->resolver.cache_rtt;
+	for (size_t i = 0; i < table->size; ++i) {
+		if (!table->slots[i].key)
+			continue;
+		if (table->slots[i].data > KR_NS_LONG) {
+			lru_evict(table, i);
+		}
+	}
+}
+
 int engine_init(struct engine *engine, knot_mm_t *pool)
 {
 	if (engine == NULL) {
@@ -607,11 +626,23 @@ int engine_start(struct engine *engine, const char *config_path)
 	lua_gc(engine->L, LUA_GCSETSTEPMUL, 50);
 	lua_gc(engine->L, LUA_GCSETPAUSE, 400);
 	lua_gc(engine->L, LUA_GCRESTART, 0);
+
+	/* Set up periodic update function */
+	uv_timer_t *timer = malloc(sizeof(*timer));
+	if (timer) {
+		uv_timer_init(uv_default_loop(), timer);
+		timer->data = engine;
+		engine->updater = timer;
+		uv_timer_start(timer, update_state, CLEANUP_TIMER, CLEANUP_TIMER);
+	}
+
 	return kr_ok();
 }
 
 void engine_stop(struct engine *engine)
 {
+	uv_timer_stop(engine->updater);
+	uv_close((uv_handle_t *)engine->updater, (uv_close_cb) free);
 	uv_stop(uv_default_loop());
 }
 
diff --git a/daemon/engine.h b/daemon/engine.h
index 7c9379939..1eddda633 100644
--- a/daemon/engine.h
+++ b/daemon/engine.h
@@ -59,6 +59,7 @@ struct engine {
     module_array_t modules;
     storage_registry_t storage_registry;
     knot_mm_t *pool;
+    uv_timer_t *updater;
     struct lua_State *L;
 };
 
diff --git a/lib/generic/lru.h b/lib/generic/lru.h
index 94eaa8a6d..93348326c 100644
--- a/lib/generic/lru.h
+++ b/lib/generic/lru.h
@@ -116,6 +116,9 @@ struct { \
 /** Get slot at given index. */
 static inline void *lru_slot_at(struct lru_hash_base *lru, uint32_t id)
 {
+	if (id >= lru->size) {
+		return NULL;
+	}
 	return (struct lru_slot *)(lru->slots + (id * lru->stride));
 }
 
@@ -139,6 +142,21 @@ static inline void *lru_slot_get(struct lru_hash_base *lru, const char *key, uin
 	return NULL;
 }
 
+static inline int lru_slot_evict(struct lru_hash_base *lru, uint32_t id, size_t offset)
+{
+	struct lru_slot *slot = lru_slot_at(lru, id);
+	if (!slot || !slot->key) {
+		return -1;
+	}
+	lru->evictions += 1;
+	free(slot->key);
+	if (lru->evict) {
+		lru->evict(lru->baton, lru_slot_val(slot, offset));
+	}
+	memset(slot, 0, lru->stride);
+	return 0;
+}
+
 /** @internal Slot data setter */
 static inline void *lru_slot_set(struct lru_hash_base *lru, const char *key, uint16_t len, size_t offset)
 {
@@ -155,10 +173,8 @@ static inline void *lru_slot_set(struct lru_hash_base *lru, const char *key, uin
 			if (slot->refs > 0) {
 				return NULL; /* Couldn't joust former key. */
 			}
-			lru->evictions += 1;
-			free(slot->key);
-			if (lru->evict) {
-				lru->evict(lru->baton, lru_slot_val(slot, offset));
+			if (lru_slot_evict(lru, id, offset) < 0) {
+				return NULL;
 			}
 		}
 		memset(slot, 0, lru->stride);
@@ -227,4 +243,13 @@ static inline void *lru_slot_set(struct lru_hash_base *lru, const char *key, uin
  	(__typeof__(&(table)->slots[0].data)) \
 		lru_slot_set((struct lru_hash_base *)(table), (key_), (len_), lru_slot_offset(table))
 
+/**
+ * @brief Evict element at index.
+ * @param table hash table
+ * @param pos_ element position
+ * @return 0 if successful, negative integer if failed
+ */
+#define lru_evict(table, pos_) \
+ 	lru_slot_evict((struct lru_hash_base *)(table), (pos_), lru_slot_offset(table))
+
 /** @} */