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Elector.cc
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Elector.cc
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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#include "Elector.h"
#include "Monitor.h"
#include "common/Timer.h"
#include "MonitorDBStore.h"
#include "messages/MMonElection.h"
#include "common/config.h"
#include "include/ceph_assert.h"
#define dout_subsys ceph_subsys_mon
#undef dout_prefix
#define dout_prefix _prefix(_dout, mon, get_epoch())
static ostream& _prefix(std::ostream *_dout, Monitor *mon, epoch_t epoch) {
return *_dout << "mon." << mon->name << "@" << mon->rank
<< "(" << mon->get_state_name()
<< ").elector(" << epoch << ") ";
}
Elector::Elector(Monitor *m) : logic(this, m->cct),
mon(m), elector(this) {}
void Elector::persist_epoch(epoch_t e)
{
auto t(std::make_shared<MonitorDBStore::Transaction>());
t->put(Monitor::MONITOR_NAME, "election_epoch", e);
mon->store->apply_transaction(t);
}
epoch_t Elector::read_persisted_epoch() const
{
return mon->store->get(Monitor::MONITOR_NAME, "election_epoch");
}
void Elector::validate_store()
{
auto t(std::make_shared<MonitorDBStore::Transaction>());
t->put(Monitor::MONITOR_NAME, "election_writeable_test", rand());
int r = mon->store->apply_transaction(t);
ceph_assert(r >= 0);
}
bool Elector::is_current_member(int rank) const
{
return mon->quorum.count(rank);
}
void Elector::trigger_new_election()
{
mon->start_election();
}
int Elector::get_my_rank() const
{
return mon->rank;
}
void Elector::reset_election()
{
mon->bootstrap();
}
bool Elector::ever_participated() const
{
return mon->has_ever_joined;
}
unsigned Elector::paxos_size() const
{
return (unsigned)mon->monmap->size();
}
void Elector::shutdown()
{
cancel_timer();
}
void Elector::notify_bump_epoch()
{
mon->join_election();
}
void Elector::propose_to_peers(epoch_t e)
{
// bcast to everyone else
for (unsigned i=0; i<mon->monmap->size(); ++i) {
if ((int)i == mon->rank) continue;
MMonElection *m =
new MMonElection(MMonElection::OP_PROPOSE, e, mon->monmap);
m->mon_features = ceph::features::mon::get_supported();
m->mon_release = ceph_release();
mon->send_mon_message(m, i);
}
}
void Elector::_start()
{
peer_info.clear();
peer_info[mon->rank].cluster_features = CEPH_FEATURES_ALL;
peer_info[mon->rank].mon_release = ceph_release();
peer_info[mon->rank].mon_features = ceph::features::mon::get_supported();
mon->collect_metadata(&peer_info[mon->rank].metadata);
reset_timer();
}
void Elector::_defer_to(int who)
{
MMonElection *m = new MMonElection(MMonElection::OP_ACK, get_epoch(), mon->monmap);
m->mon_features = ceph::features::mon::get_supported();
m->mon_release = ceph_release();
mon->collect_metadata(&m->metadata);
mon->send_mon_message(m, who);
// set a timer
reset_timer(1.0); // give the leader some extra time to declare victory
}
void Elector::reset_timer(double plus)
{
// set the timer
cancel_timer();
/**
* This class is used as the callback when the expire_event timer fires up.
*
* If the expire_event is fired, then it means that we had an election going,
* either started by us or by some other participant, but it took too long,
* thus expiring.
*
* When the election expires, we will check if we were the ones who won, and
* if so we will declare victory. If that is not the case, then we assume
* that the one we defered to didn't declare victory quickly enough (in fact,
* as far as we know, we may even be dead); so, just propose ourselves as the
* Leader.
*/
expire_event = mon->timer.add_event_after(
g_conf()->mon_election_timeout + plus,
new C_MonContext(mon, [this](int) {
logic.end_election_period();
}));
}
void Elector::cancel_timer()
{
if (expire_event) {
mon->timer.cancel_event(expire_event);
expire_event = 0;
}
}
void Elector::message_victory(const std::set<int>& quorum)
{
uint64_t cluster_features = CEPH_FEATURES_ALL;
mon_feature_t mon_features = ceph::features::mon::get_supported();
map<int,Metadata> metadata;
ceph_release_t min_mon_release{ceph_release_t::unknown};
for (auto id : quorum) {
auto i = peer_info.find(id);
ceph_assert(i != peer_info.end());
auto& info = i->second;
cluster_features &= info.cluster_features;
mon_features &= info.mon_features;
metadata[id] = info.metadata;
if (min_mon_release == ceph_release_t::unknown ||
info.mon_release < min_mon_release) {
min_mon_release = info.mon_release;
}
}
cancel_timer();
// tell everyone!
for (set<int>::iterator p = quorum.begin();
p != quorum.end();
++p) {
if (*p == mon->rank) continue;
MMonElection *m = new MMonElection(MMonElection::OP_VICTORY, get_epoch(),
mon->monmap);
m->quorum = quorum;
m->quorum_features = cluster_features;
m->mon_features = mon_features;
m->sharing_bl = mon->get_local_commands_bl(mon_features);
m->mon_release = min_mon_release;
mon->send_mon_message(m, *p);
}
// tell monitor
mon->win_election(get_epoch(), quorum,
cluster_features, mon_features, min_mon_release,
metadata);
}
void Elector::handle_propose(MonOpRequestRef op)
{
op->mark_event("elector:handle_propose");
MMonElection *m = static_cast<MMonElection*>(op->get_req());
dout(5) << "handle_propose from " << m->get_source() << dendl;
int from = m->get_source().num();
ceph_assert(m->epoch % 2 == 1); // election
uint64_t required_features = mon->get_required_features();
mon_feature_t required_mon_features = mon->get_required_mon_features();
dout(10) << __func__ << " required features " << required_features
<< " " << required_mon_features
<< ", peer features " << m->get_connection()->get_features()
<< " " << m->mon_features
<< dendl;
if ((required_features ^ m->get_connection()->get_features()) &
required_features) {
dout(5) << " ignoring propose from mon" << from
<< " without required features" << dendl;
nak_old_peer(op);
return;
} else if (mon->monmap->min_mon_release > m->mon_release) {
dout(5) << " ignoring propose from mon" << from
<< " release " << (int)m->mon_release
<< " < min_mon_release " << (int)mon->monmap->min_mon_release
<< dendl;
nak_old_peer(op);
return;
} else if (!m->mon_features.contains_all(required_mon_features)) {
// all the features in 'required_mon_features' not in 'm->mon_features'
mon_feature_t missing = required_mon_features.diff(m->mon_features);
dout(5) << " ignoring propose from mon." << from
<< " without required mon_features " << missing
<< dendl;
nak_old_peer(op);
}
logic.receive_propose(from, m->epoch);
}
void Elector::handle_ack(MonOpRequestRef op)
{
op->mark_event("elector:handle_ack");
MMonElection *m = static_cast<MMonElection*>(op->get_req());
dout(5) << "handle_ack from " << m->get_source() << dendl;
int from = m->get_source().num();
ceph_assert(m->epoch == get_epoch());
uint64_t required_features = mon->get_required_features();
if ((required_features ^ m->get_connection()->get_features()) &
required_features) {
dout(5) << " ignoring ack from mon" << from
<< " without required features" << dendl;
return;
}
mon_feature_t required_mon_features = mon->get_required_mon_features();
if (!m->mon_features.contains_all(required_mon_features)) {
mon_feature_t missing = required_mon_features.diff(m->mon_features);
dout(5) << " ignoring ack from mon." << from
<< " without required mon_features " << missing
<< dendl;
return;
}
if (logic.electing_me) {
// thanks
peer_info[from].cluster_features = m->get_connection()->get_features();
peer_info[from].mon_features = m->mon_features;
peer_info[from].mon_release = m->mon_release;
peer_info[from].metadata = m->metadata;
dout(5) << " so far i have {";
for (auto q = logic.acked_me.begin();
q != logic.acked_me.end();
++q) {
auto p = peer_info.find(*q);
ceph_assert(p != peer_info.end());
if (q != logic.acked_me.begin())
*_dout << ",";
*_dout << " mon." << p->first << ":"
<< " features " << p->second.cluster_features
<< " " << p->second.mon_features;
}
*_dout << " }" << dendl;
}
logic.receive_ack(from, m->epoch);
}
void Elector::handle_victory(MonOpRequestRef op)
{
op->mark_event("elector:handle_victory");
MMonElection *m = static_cast<MMonElection*>(op->get_req());
dout(5) << "handle_victory from " << m->get_source()
<< " quorum_features " << m->quorum_features
<< " " << m->mon_features
<< dendl;
int from = m->get_source().num();
bool accept_victory = logic.receive_victory_claim(from, m->epoch);
if (!accept_victory) {
return;
}
mon->lose_election(get_epoch(), m->quorum, from,
m->quorum_features, m->mon_features, m->mon_release);
// cancel my timer
cancel_timer();
// stash leader's commands
ceph_assert(m->sharing_bl.length());
vector<MonCommand> new_cmds;
auto bi = m->sharing_bl.cbegin();
MonCommand::decode_vector(new_cmds, bi);
mon->set_leader_commands(new_cmds);
}
void Elector::nak_old_peer(MonOpRequestRef op)
{
op->mark_event("elector:nak_old_peer");
MMonElection *m = static_cast<MMonElection*>(op->get_req());
uint64_t supported_features = m->get_connection()->get_features();
uint64_t required_features = mon->get_required_features();
mon_feature_t required_mon_features = mon->get_required_mon_features();
dout(10) << "sending nak to peer " << m->get_source()
<< " supports " << supported_features << " " << m->mon_features
<< ", required " << required_features << " " << required_mon_features
<< ", release " << (int)m->mon_release
<< " vs required " << (int)mon->monmap->min_mon_release
<< dendl;
MMonElection *reply = new MMonElection(MMonElection::OP_NAK, m->epoch,
mon->monmap);
reply->quorum_features = required_features;
reply->mon_features = required_mon_features;
reply->mon_release = mon->monmap->min_mon_release;
mon->features.encode(reply->sharing_bl);
m->get_connection()->send_message(reply);
}
void Elector::handle_nak(MonOpRequestRef op)
{
op->mark_event("elector:handle_nak");
MMonElection *m = static_cast<MMonElection*>(op->get_req());
dout(1) << "handle_nak from " << m->get_source()
<< " quorum_features " << m->quorum_features
<< " " << m->mon_features
<< " min_mon_release " << (int)m->mon_release
<< dendl;
if (m->mon_release > ceph_release()) {
derr << "Shutting down because I am release " << (int)ceph_release()
<< " < min_mon_release " << (int)m->mon_release << dendl;
} else {
CompatSet other;
auto bi = m->sharing_bl.cbegin();
other.decode(bi);
CompatSet diff = Monitor::get_supported_features().unsupported(other);
mon_feature_t mon_supported = ceph::features::mon::get_supported();
// all features in 'm->mon_features' not in 'mon_supported'
mon_feature_t mon_diff = m->mon_features.diff(mon_supported);
derr << "Shutting down because I lack required monitor features: { "
<< diff << " } " << mon_diff << dendl;
}
exit(0);
// the end!
}
void Elector::dispatch(MonOpRequestRef op)
{
op->mark_event("elector:dispatch");
ceph_assert(op->is_type_election());
switch (op->get_req()->get_type()) {
case MSG_MON_ELECTION:
{
if (!logic.participating) {
return;
}
if (op->get_req()->get_source().num() >= mon->monmap->size()) {
dout(5) << " ignoring bogus election message with bad mon rank "
<< op->get_req()->get_source() << dendl;
return;
}
MMonElection *em = static_cast<MMonElection*>(op->get_req());
// assume an old message encoding would have matched
if (em->fsid != mon->monmap->fsid) {
dout(0) << " ignoring election msg fsid "
<< em->fsid << " != " << mon->monmap->fsid << dendl;
return;
}
if (!mon->monmap->contains(em->get_source_addr())) {
dout(1) << "discarding election message: " << em->get_source_addr()
<< " not in my monmap " << *mon->monmap << dendl;
return;
}
MonMap peermap;
peermap.decode(em->monmap_bl);
if (peermap.epoch > mon->monmap->epoch) {
dout(0) << em->get_source_inst() << " has newer monmap epoch " << peermap.epoch
<< " > my epoch " << mon->monmap->epoch
<< ", taking it"
<< dendl;
mon->monmap->decode(em->monmap_bl);
auto t(std::make_shared<MonitorDBStore::Transaction>());
t->put("monmap", mon->monmap->epoch, em->monmap_bl);
t->put("monmap", "last_committed", mon->monmap->epoch);
mon->store->apply_transaction(t);
//mon->monmon()->paxos->stash_latest(mon->monmap->epoch, em->monmap_bl);
cancel_timer();
mon->bootstrap();
return;
}
if (peermap.epoch < mon->monmap->epoch) {
dout(0) << em->get_source_inst() << " has older monmap epoch " << peermap.epoch
<< " < my epoch " << mon->monmap->epoch
<< dendl;
}
switch (em->op) {
case MMonElection::OP_PROPOSE:
handle_propose(op);
return;
}
if (em->epoch < get_epoch()) {
dout(5) << "old epoch, dropping" << dendl;
break;
}
switch (em->op) {
case MMonElection::OP_ACK:
handle_ack(op);
return;
case MMonElection::OP_VICTORY:
handle_victory(op);
return;
case MMonElection::OP_NAK:
handle_nak(op);
return;
default:
ceph_abort();
}
}
break;
default:
ceph_abort();
}
}
void Elector::start_participating()
{
logic.participating = true;
}