static int process_REVOKE (
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
int rv;
if (tk->state == ST_INIT && tk->leader == no_leader) {
/* assume that our ack got lost */
rv = send_msg(OP_ACK, tk, sender, msg);
} else if (tk->leader != sender) {
tk_log_error("%s wants to revoke ticket, "
"but it is not granted there (ignoring)",
site_string(sender));
return 1;
} else if (tk->state != ST_FOLLOWER) {
tk_log_error("unexpected ticket revoke from %s "
"(in state %s) (ignoring)",
site_string(sender),
state_to_string(tk->state));
return 1;
} else {
tk_log_info("%s revokes ticket",
site_string(tk->leader));
save_committed_tkt(tk);
reset_ticket(tk);
set_leader(tk, no_leader);
ticket_write(tk);
rv = send_msg(OP_ACK, tk, sender, msg);
}
return rv;
}
static int test_reason(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
int reason;
reason = ntohl(msg->header.reason);
if (reason == OR_TKT_LOST) {
if (tk->state == ST_INIT &&
tk->leader == no_leader) {
tk_log_warn("%s claims that the ticket is lost, "
"but it's in %s state (reject sent)",
site_string(sender),
state_to_string(tk->state)
);
return RLT_YOU_OUTDATED;
}
if (ticket_seems_ok(tk)) {
tk_log_warn("%s claims that the ticket is lost, "
"but it is ok here (reject sent)",
site_string(sender));
return RLT_TERM_STILL_VALID;
}
}
return 0;
}
static int process_UPDATE (
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
if (is_owned(tk) && sender != tk->leader) {
tk_log_warn("different leader %s wants to update "
"our ticket, sending reject",
site_string(leader));
return send_reject(sender, tk, RLT_TERM_OUTDATED, msg);
}
tk_log_debug("leader %s wants to update our ticket",
site_string(leader));
become_follower(tk, msg);
set_leader(tk, leader);
ticket_write(tk);
/* run ticket_cron if the ticket expires */
set_ticket_wakeup(tk);
return send_msg(OP_ACK, tk, sender, msg);
}
/* we were a leader and somebody says that they have a more up
* to date ticket
* there was probably connectivity loss
* tricky
*/
static int leader_handle_newer_ticket(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
update_term_from_msg(tk, msg);
if (leader != no_leader && leader && leader != local) {
/* eek, two leaders, split brain */
/* normally shouldn't happen; run election */
tk_log_error("from %s: ticket granted to %s! (revoking locally)",
site_string(sender),
site_string(leader)
);
} else if (term_time_left(tk)) {
/* eek, two leaders, split brain */
/* normally shouldn't happen; run election */
tk_log_error("from %s: ticket granted to %s! (revoking locally)",
site_string(sender),
site_string(leader)
);
}
set_next_state(tk, ST_LEADER);
return 0;
}
/* §5.2 */
static int answer_REQ_VOTE(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
int valid;
struct boothc_ticket_msg omsg;
cmd_result_t inappr_reason;
int reason;
inappr_reason = test_reason(tk, sender, leader, msg);
if (inappr_reason)
return send_reject(sender, tk, inappr_reason, msg);
valid = term_time_left(tk);
reason = ntohl(msg->header.reason);
/* valid tickets are not allowed only if the sender thinks
* the ticket got lost */
if (sender != tk->leader && valid && reason != OR_STEPDOWN) {
tk_log_warn("election from %s with reason %s rejected "
"(we have %s as ticket owner), ticket still valid for %ds",
site_string(sender), state_to_string(reason),
site_string(tk->leader), valid);
return send_reject(sender, tk, RLT_TERM_STILL_VALID, msg);
}
if (term_too_low(tk, sender, leader, msg))
return 0;
/* set this, so that we know not to send status for the
* ticket */
tk->in_election = 1;
/* reset ticket's leader on not valid tickets */
if (!valid)
set_leader(tk, NULL);
/* if it's a newer term or ... */
if (newer_term(tk, sender, leader, msg, 1)) {
clear_election(tk);
goto vote_for_sender;
}
/* ... we didn't vote yet, then vote for the sender */
/* §5.2, §5.4 */
if (!tk->voted_for) {
vote_for_sender:
tk->voted_for = sender;
record_vote(tk, sender, leader);
}
init_ticket_msg(&omsg, OP_VOTE_FOR, OP_REQ_VOTE, RLT_SUCCESS, 0, tk);
omsg.ticket.leader = htonl(get_node_id(tk->voted_for));
return booth_udp_send_auth(sender, &omsg, sendmsglen(&omsg));
}
static int newer_term(struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg,
int in_election)
{
uint32_t term;
/* it may happen that we hear about our newer term */
if (leader == local)
return 0;
term = ntohl(msg->ticket.term);
/* §5.1 */
if (term > tk->current_term) {
set_state(tk, ST_FOLLOWER);
if (!in_election) {
set_leader(tk, leader);
tk_log_info("from %s: higher term %d vs. %d, following %s",
site_string(sender),
term, tk->current_term,
ticket_leader_string(tk));
} else {
tk_log_debug("from %s: higher term %d vs. %d (election)",
site_string(sender),
term, tk->current_term);
}
tk->current_term = term;
return 1;
}
return 0;
}
static struct booth_site *majority_votes(struct ticket_config *tk)
{
int i, n;
struct booth_site *v;
int count[MAX_NODES] = { 0, };
for(i=0; i<booth_conf->site_count; i++) {
v = tk->votes_for[i];
if (!v || v == no_leader)
continue;
n = v->index;
count[n]++;
tk_log_debug("Majority: %d %s wants %d %s => %d",
i, site_string(&booth_conf->site[i]),
n, site_string(v),
count[n]);
if (count[n]*2 <= booth_conf->site_count)
continue;
tk_log_debug("Majority reached: %d of %d for %s",
count[n], booth_conf->site_count,
site_string(v));
return v;
}
return NULL;
}
static int process_VOTE_FOR(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
if (leader == no_leader) {
/* leader wants to step down? */
if (sender == tk->leader &&
(tk->state == ST_FOLLOWER || tk->state == ST_CANDIDATE)) {
tk_log_info("%s wants to give the ticket away (ticket release)",
site_string(tk->leader));
save_committed_tkt(tk);
reset_ticket(tk);
set_state(tk, ST_FOLLOWER);
if (local->type == SITE) {
ticket_write(tk);
schedule_election(tk, OR_STEPDOWN);
}
} else {
tk_log_info("%s votes for none, ignoring (duplicate ticket release?)",
site_string(sender));
}
return 0;
}
if (tk->state != ST_CANDIDATE) {
/* lost candidate status, somebody rejected our proposal */
tk_log_info("candidate status lost, ignoring VtFr from %s",
site_string(sender));
return 0;
}
if (term_too_low(tk, sender, leader, msg))
return 0;
if (newer_term(tk, sender, leader, msg, 0)) {
clear_election(tk);
}
record_vote(tk, sender, leader);
/* only if all voted can we take the ticket now, otherwise
* wait for timeout in ticket_cron */
if (!tk->acks_expected) {
/* §5.2 */
elections_end(tk);
}
return 0;
}
/* For leader. */
static int process_ACK(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
uint32_t term;
int req;
term = ntohl(msg->ticket.term);
if (newer_term(tk, sender, leader, msg, 0)) {
/* unexpected higher term */
tk_log_warn("got higher term from %s (%d vs. %d)",
site_string(sender),
term, tk->current_term);
return 0;
}
/* Don't send a reject. */
if (term < tk->current_term) {
/* Doesn't know what he's talking about - perhaps
* doesn't receive our packets? */
tk_log_warn("unexpected term "
"from %s (%d vs. %d) (ignoring)",
site_string(sender),
term, tk->current_term);
return 0;
}
/* if the ticket is to be revoked, further processing is not
* interesting (and dangerous) */
if (tk->next_state == ST_INIT || tk->state == ST_INIT)
return 0;
req = ntohl(msg->header.request);
if ((req == OP_UPDATE || req == OP_HEARTBEAT) &&
term == tk->current_term &&
leader == tk->leader) {
if (majority_of_bits(tk, tk->acks_received)) {
/* OK, at least half of the nodes are reachable;
* Update the ticket and send update messages out
*/
return leader_update_ticket(tk);
}
}
return 0;
}
void elections_end(struct ticket_config *tk)
{
struct booth_site *new_leader;
if (is_past(&tk->election_end)) {
/* This is previous election timed out */
tk_log_info("elections finished");
}
tk->in_election = 0;
new_leader = majority_votes(tk);
if (new_leader == local) {
won_elections(tk);
tk_log_info("granted successfully here");
} else if (new_leader) {
tk_log_info("ticket granted at %s",
site_string(new_leader));
} else {
tk_log_info("nobody won elections, new elections");
tk->outcome = RLT_MORE;
foreach_tkt_req(tk, notify_client);
if (!new_election(tk, NULL, is_tie(tk) ? 2 : 0, OR_AGAIN)) {
ticket_activate_timeout(tk);
}
}
}
static void log_reacquire_reason(struct ticket_config *tk)
{
int valid;
const char *where_granted = "\0";
char buff[64];
valid = is_time_set(&tk->term_expires) && !is_past(&tk->term_expires);
if (tk->leader == local) {
where_granted = "granted here";
} else {
snprintf(buff, sizeof(buff), "granted to %s",
site_string(tk->leader));
where_granted = buff;
}
if (!valid) {
tk_log_warn("%s, but not valid "
"anymore (will try to reacquire)", where_granted);
}
if (tk->is_granted && tk->leader != local) {
if (tk->leader && tk->leader != no_leader) {
tk_log_error("granted here, but also %s, "
"that's really too bad (will try to reacquire)",
where_granted);
} else {
tk_log_warn("granted here, but we're "
"not recorded as the grantee (will try to reacquire)");
}
}
}
inline static void record_vote(struct ticket_config *tk,
struct booth_site *who,
struct booth_site *vote)
{
tk_log_debug("site %s votes for %s",
site_string(who),
site_string(vote));
if (!tk->votes_for[who->index]) {
tk->votes_for[who->index] = vote;
tk->votes_received |= who->bitmask;
} else {
if (tk->votes_for[who->index] != vote)
tk_log_warn("%s voted previously "
"for %s and now wants to vote for %s (ignored)",
site_string(who),
site_string(tk->votes_for[who->index]),
site_string(vote));
}
}
/* For follower. */
static int answer_HEARTBEAT (
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
uint32_t term;
term = ntohl(msg->ticket.term);
tk_log_debug("heartbeat from leader: %s, have %s; term %d vs %d",
site_string(leader), ticket_leader_string(tk),
term, tk->current_term);
if (term < tk->current_term) {
if (sender == tk->leader) {
tk_log_info("trusting leader %s with a lower term (%d vs %d)",
site_string(leader), term, tk->current_term);
} else if (is_owned(tk)) {
tk_log_warn("different leader %s with a lower term "
"(%d vs %d), sending reject",
site_string(leader), term, tk->current_term);
return send_reject(sender, tk, RLT_TERM_OUTDATED, msg);
}
}
/* got heartbeat, no rejects expected anymore */
tk->expect_more_rejects = 0;
/* Needed? */
newer_term(tk, sender, leader, msg, 0);
become_follower(tk, msg);
/* Racy??? */
assert(sender == leader || !leader);
set_leader(tk, leader);
/* Ack the heartbeat (we comply). */
return send_msg(OP_ACK, tk, sender, msg);
}
static void update_ticket_from_msg(struct ticket_config *tk,
struct booth_site *sender,
struct boothc_ticket_msg *msg)
{
int duration;
tk_log_info("updating from %s (%d/%d)",
site_string(sender),
ntohl(msg->ticket.term), msg_term_time(msg));
duration = min(tk->term_duration, msg_term_time(msg));
set_ticket_expiry(tk, duration);
update_term_from_msg(tk, msg);
}
static int msg_term_invalid(struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg)
{
uint32_t term;
term = ntohl(msg->ticket.term);
/* §5.1 */
if (is_term_invalid(tk, term)) {
tk_log_info("got invalid term from %s "
"(%d), ignoring", site_string(sender), term);
return 1;
}
return 0;
}
void update_ticket_state(struct ticket_config *tk, struct booth_site *sender)
{
if (tk->state == ST_CANDIDATE) {
tk_log_info("learned from %s about "
"newer ticket, stopping elections",
site_string(sender));
/* there could be rejects coming from others; don't log
* warnings unnecessarily */
tk->expect_more_rejects = 1;
}
if (tk->leader == local || tk->is_granted) {
/* message from a live leader with valid ticket? */
if (sender == tk->leader && term_time_left(tk)) {
if (tk->is_granted) {
tk_log_warn("ticket was granted here, "
"but it's live at %s (revoking here)",
site_string(sender));
} else {
tk_log_info("ticket live at %s",
site_string(sender));
}
disown_ticket(tk);
ticket_write(tk);
set_state(tk, ST_FOLLOWER);
set_next_state(tk, ST_FOLLOWER);
} else {
if (tk->state == ST_CANDIDATE) {
set_state(tk, ST_FOLLOWER);
}
set_next_state(tk, ST_LEADER);
}
} else {
if (!tk->leader || tk->leader == no_leader) {
if (sender)
tk_log_info("ticket is not granted");
else
tk_log_info("ticket is not granted (from CIB)");
set_state(tk, ST_INIT);
} else {
if (sender)
tk_log_info("ticket granted to %s (says %s)",
site_string(tk->leader),
tk->leader == sender ? "they" : site_string(sender));
else
tk_log_info("ticket granted to %s (from CIB)",
site_string(tk->leader));
set_state(tk, ST_FOLLOWER);
/* just make sure that we check the ticket soon */
set_next_state(tk, ST_FOLLOWER);
}
}
}
static int term_too_low(struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg)
{
uint32_t term;
term = ntohl(msg->ticket.term);
/* §5.1 */
if (term < tk->current_term) {
tk_log_info("sending reject to %s, its term too low "
"(%d vs. %d)", site_string(sender),
term, tk->current_term
);
send_reject(sender, tk, RLT_TERM_OUTDATED, msg);
return 1;
}
return 0;
}
int raft_answer(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
int cmd, req;
int rv;
rv = 0;
cmd = ntohl(msg->header.cmd);
req = ntohl(msg->header.request);
if (req)
tk_log_debug("got %s (req %s) from %s",
state_to_string(cmd),
state_to_string(req),
site_string(sender));
else
tk_log_debug("got %s from %s",
state_to_string(cmd),
site_string(sender));
/* don't process tickets with invalid term
*/
if (cmd != OP_STATUS &&
msg_term_invalid(tk, sender, leader, msg))
return 0;
switch (cmd) {
case OP_REQ_VOTE:
rv = answer_REQ_VOTE(tk, sender, leader, msg);
break;
case OP_VOTE_FOR:
rv = process_VOTE_FOR(tk, sender, leader, msg);
break;
case OP_ACK:
if (tk->leader == local &&
tk->state == ST_LEADER)
rv = process_ACK(tk, sender, leader, msg);
break;
case OP_HEARTBEAT:
if ((tk->leader != local || !term_time_left(tk)) &&
(tk->state == ST_INIT || tk->state == ST_FOLLOWER ||
tk->state == ST_CANDIDATE))
rv = answer_HEARTBEAT(tk, sender, leader, msg);
else {
tk_log_warn("unexpected message %s, from %s",
state_to_string(cmd),
site_string(sender));
if (ticket_seems_ok(tk))
send_reject(sender, tk, RLT_TERM_STILL_VALID, msg);
rv = -EINVAL;
}
break;
case OP_UPDATE:
if (((tk->leader != local && tk->leader == leader) || !is_owned(tk)) &&
(tk->state == ST_INIT || tk->state == ST_FOLLOWER ||
tk->state == ST_CANDIDATE)) {
rv = process_UPDATE(tk, sender, leader, msg);
} else {
tk_log_warn("unexpected message %s, from %s",
state_to_string(cmd),
site_string(sender));
if (ticket_seems_ok(tk))
send_reject(sender, tk, RLT_TERM_STILL_VALID, msg);
rv = -EINVAL;
}
break;
case OP_REJECTED:
rv = process_REJECTED(tk, sender, leader, msg);
break;
case OP_REVOKE:
rv = process_REVOKE(tk, sender, leader, msg);
break;
case OP_MY_INDEX:
rv = process_MY_INDEX(tk, sender, leader, msg);
break;
case OP_STATUS:
if (!tk->in_election)
rv = send_msg(OP_MY_INDEX, tk, sender, msg);
break;
default:
tk_log_error("unknown message %s, from %s",
state_to_string(cmd), site_string(sender));
rv = -EINVAL;
}
return rv;
}
/* reply to STATUS */
static int process_MY_INDEX (
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
int i;
int expired;
expired = !msg_term_time(msg);
/* test against the last valid(!) ticket we have */
i = my_last_term(tk) - ntohl(msg->ticket.term);
if (i > 0) {
/* let them know about our newer ticket */
send_msg(OP_MY_INDEX, tk, sender, msg);
if (tk->state == ST_LEADER) {
tk_log_info("sending ticket update to %s",
site_string(sender));
return send_msg(OP_UPDATE, tk, sender, msg);
}
}
/* we have a newer or equal ticket and theirs is expired,
* nothing more to do here */
if (i >= 0 && expired) {
return 0;
}
if (tk->state == ST_LEADER) {
/* we're the leader, thread carefully */
if (expired) {
/* if their ticket is expired,
* nothing more to do */
return 0;
}
if (i < 0) {
/* they have a newer ticket, trouble if we're already leader
* for it */
tk_log_warn("from %s: more up to date ticket at %s",
site_string(sender),
site_string(leader)
);
return leader_handle_newer_ticket(tk, sender, leader, msg);
} else {
/* we have the ticket and we don't care */
return 0;
}
} else if (tk->state == ST_CANDIDATE) {
if (leader == local) {
/* a belated MY_INDEX, we're already trying to get the
* ticket */
return 0;
}
}
/* their ticket is either newer or not expired, don't
* ignore it */
update_ticket_from_msg(tk, sender, msg);
set_leader(tk, leader);
update_ticket_state(tk, sender);
save_committed_tkt(tk);
set_ticket_wakeup(tk);
return 0;
}
static int process_REJECTED(
struct ticket_config *tk,
struct booth_site *sender,
struct booth_site *leader,
struct boothc_ticket_msg *msg
)
{
uint32_t rv;
rv = ntohl(msg->header.result);
if (tk->state == ST_CANDIDATE &&
leader == local) {
/* the sender has us as the leader (!)
* the elections will time out, then we can try again
*/
tk_log_warn("ticket was granted to us "
"(and we didn't know)");
tk->expect_more_rejects = 1;
return 0;
}
if (tk->state == ST_CANDIDATE &&
rv == RLT_TERM_OUTDATED) {
tk_log_warn("ticket outdated (term %d), granted to %s",
ntohl(msg->ticket.term),
site_string(leader)
);
set_leader(tk, leader);
tk->expect_more_rejects = 1;
become_follower(tk, msg);
return 0;
}
if (tk->state == ST_CANDIDATE &&
rv == RLT_TERM_STILL_VALID) {
if (tk->lost_leader == leader) {
if (tk->election_reason == OR_TKT_LOST) {
tk_log_warn("%s still has the ticket valid, "
"we'll backup a bit",
site_string(sender));
} else {
tk_log_warn("%s unexpectedly rejects elections",
site_string(sender));
}
} else {
tk_log_warn("ticket was granted to %s "
"(and we didn't know)",
site_string(leader));
}
set_leader(tk, leader);
become_follower(tk, msg);
tk->expect_more_rejects = 1;
return 0;
}
if (tk->state == ST_CANDIDATE &&
rv == RLT_YOU_OUTDATED) {
set_leader(tk, leader);
tk->expect_more_rejects = 1;
if (leader && leader != no_leader) {
tk_log_warn("our ticket is outdated, granted to %s",
site_string(leader));
become_follower(tk, msg);
} else {
tk_log_warn("our ticket is outdated and revoked");
update_ticket_from_msg(tk, sender, msg);
set_state(tk, ST_INIT);
}
return 0;
}
if (!tk->expect_more_rejects) {
tk_log_warn("from %s: in state %s, got %s (unexpected reject)",
site_string(sender),
state_to_string(tk->state),
state_to_string(rv));
}
return 0;
}
