/**
* Record activity on the node.
*/
void
stable_record_activity(const knode_t *kn)
{
struct lifedata *ld;
struct lifedata new_ld;
knode_check(kn);
g_assert(kn->flags & KNODE_F_ALIVE);
ld = get_lifedata(kn->id);
if (NULL == ld) {
ld = &new_ld;
new_ld.version = LIFEDATA_STRUCT_VERSION;
new_ld.first_seen = kn->first_seen;
new_ld.last_seen = kn->last_seen;
gnet_stats_count_general(GNR_DHT_STABLE_NODES_HELD, +1);
} else {
if (kn->last_seen <= ld->last_seen)
return;
ld->last_seen = kn->last_seen;
}
dbmw_write(db_lifedata, kn->id->v, ld, sizeof *ld);
}
/**
* The KUID of the node has changed: remove its entry if it had one and make
* sure we have an entry for the new KUID.
*
* @param kn the old node
* @param rn the replacing node
*/
void
stable_replace(const knode_t *kn, const knode_t *rn)
{
struct lifedata *ld;
knode_check(kn);
knode_check(rn);
g_assert(rn->flags & KNODE_F_ALIVE);
ld = get_lifedata(kn->id);
if (NULL == ld)
return; /* Node was not recorded in the "stable" set */
if (GNET_PROPERTY(dht_stable_debug)) {
g_debug("DHT STABLE removing obsolete %s, now at %s",
knode_to_string(kn), knode_to_string2(rn));
}
/*
* Remove the old node and create an entry for the new one.
*/
dbmw_delete(db_lifedata, kn->id->v);
gnet_stats_dec_general(GNR_DHT_STABLE_NODES_HELD);
stable_record_activity(rn);
}
/**
* Estimate probability of presence for a value published to some roots in
* a given time frame.
*
* @param d how many seconds in the future?
* @param rs the STORE lookup path, giving root candidates
* @param status the array of STORE status for each entry in the path
*
* @return an estimated probability of presence of the value in the network.
*/
double
stable_store_presence(time_delta_t d,
const lookup_rs_t *rs, const guint16 *status)
{
double q = 1.0;
size_t i;
size_t count = lookup_result_path_length(rs);
/*
* We may be called by publish callbacks invoked to clean up because
* the operation was cancelled. Maybe the DHT was disabled during the
* operation, meaning our data structures have been cleaned up? In that
* case, abort immediately.
*
* NOTE: this is not an assertion, it can happen in practice and needs to
* be explicitly checked for.
*/
if (NULL == db_lifedata) /* DHT disabled dynamically */
return 0.0;
/*
* The probability of presence is (1 - q) where q is the probability
* that the value be lost by all the nodes, i.e. that all the nodes
* to which the value was published to be gone in "d" seconds.
*/
for (i = 0; i < count; i++) {
if (status[i] == STORE_SC_OK) {
const knode_t *kn = lookup_result_nth_node(rs, i);
struct lifedata *ld = get_lifedata(kn->id);
if (NULL == ld) {
return 0.0; /* Cannot compute a suitable probability */
} else {
time_delta_t alive = delta_time(ld->last_seen, ld->first_seen);
double p = stable_alive_probability(alive, d);
q *= (1.0 - p); /* (1 - p) is proba this node will be gone */
}
}
}
return 1.0 - q;
}
