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support arbiter in a new way #404

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support arbiter in a new way #404

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4 changes: 4 additions & 0 deletions src/braft/errno.proto
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Original file line number Diff line number Diff line change
Expand Up @@ -32,5 +32,9 @@ enum RaftError {
ENOMOREUSERLOG = 10015;
// Raft node in readonly mode
EREADONLY = 10016;
// Raft group not in degraded mode
ENOTDEGRADED = 10017;
// Arbiter node receives non virtual snapshot
ESNAPSHOTNOTVIRTUAL = 10018;
};

19 changes: 15 additions & 4 deletions src/braft/fsm_caller.cpp
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Expand Up @@ -298,7 +298,13 @@ void FSMCaller::do_committed(int64_t committed_index) {
continue;
}
Iterator iter(&iter_impl);
_fsm->on_apply(iter);
if (!_node->arbiter()) {
_fsm->on_apply(iter);
} else {
while(iter.valid()) {
iter.next();
}
}
LOG_IF(ERROR, iter.valid())
<< "Node " << _node->node_id()
<< " Iterator is still valid, did you return before iterator "
Expand Down Expand Up @@ -352,8 +358,11 @@ void FSMCaller::do_snapshot_save(SaveSnapshotClosure* done) {
done->Run();
return;
}

_fsm->on_snapshot_save(writer, done);
if (!_node->arbiter()) {
_fsm->on_snapshot_save(writer, done);
} else {
done->Run();
}
return;
}

Expand Down Expand Up @@ -402,7 +411,9 @@ void FSMCaller::do_snapshot_load(LoadSnapshotClosure* done) {
return done->Run();
}

ret = _fsm->on_snapshot_load(reader);
if (!_node->arbiter()) {
ret = _fsm->on_snapshot_load(reader);
}
if (ret != 0) {
done->status().set_error(ret, "StateMachine on_snapshot_load failed");
done->Run();
Expand Down
27 changes: 27 additions & 0 deletions src/braft/log_manager.cpp
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Expand Up @@ -24,6 +24,7 @@
#include <brpc/reloadable_flags.h> // BRPC_VALIDATE_GFLAG
#include "braft/storage.h" // LogStorage
#include "braft/fsm_caller.h" // FSMCaller
#include "braft/snapshot.h" // VirtualSnapshotReader

namespace braft {

Expand Down Expand Up @@ -967,4 +968,30 @@ butil::Status LogManager::check_consistency() {
return butil::Status(-1, "Impossible condition");
}

SnapshotReader* LogManager::get_virtual_snapshot() {
BAIDU_SCOPED_LOCK(_mutex);
LogId last_id;
if (_last_log_index >= _first_log_index) {
last_id = LogId(_last_log_index, unsafe_get_term(_last_log_index));
} else {
last_id = _last_snapshot_id;
}
ConfigurationEntry conf_entry;
_config_manager->get(last_id.index, &conf_entry);
SnapshotMeta meta;
meta.set_last_included_index(last_id.index);
meta.set_last_included_term(last_id.term);
for (Configuration::const_iterator
iter = conf_entry.conf.begin();
iter != conf_entry.conf.end(); ++iter) {
*meta.add_peers() = iter->to_string();
}
for (Configuration::const_iterator
iter = conf_entry.old_conf.begin();
iter != conf_entry.old_conf.end(); ++iter) {
*meta.add_old_peers() = iter->to_string();
}
return new VirtualSnapshotReader(meta);
}

} // namespace braft
2 changes: 2 additions & 0 deletions src/braft/log_manager.h
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Expand Up @@ -149,6 +149,8 @@ class BAIDU_CACHELINE_ALIGNMENT LogManager {
// Get the internal status of LogManager.
void get_status(LogManagerStatus* status);

SnapshotReader* get_virtual_snapshot();

private:
friend class AppendBatcher;
struct WaitMeta {
Expand Down
140 changes: 131 additions & 9 deletions src/braft/node.cpp
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Expand Up @@ -157,7 +157,8 @@ NodeImpl::NodeImpl(const GroupId& group_id, const PeerId& peer_id)
, _append_entries_cache(NULL)
, _append_entries_cache_version(0)
, _node_readonly(false)
, _majority_nodes_readonly(false) {
, _majority_nodes_readonly(false)
, _degraded(false) {
butil::string_printf(&_v_group_id, "%s_%d", _group_id.c_str(), _server_id.idx);
AddRef();
g_num_nodes << 1;
Expand Down Expand Up @@ -606,6 +607,7 @@ int NodeImpl::init(const NodeOptions& options) {
_state = STATE_FOLLOWER;

LOG(INFO) << "node " << _group_id << ":" << _server_id << " init,"
<< " arbiter: " << arbiter()
<< " term: " << _current_term
<< " last_log_id: " << _log_manager->last_log_id()
<< " conf: " << _conf.conf
Expand Down Expand Up @@ -771,25 +773,26 @@ void NodeImpl::on_caughtup(const PeerId& peer, int64_t term,
_conf_ctx.on_caughtup(version, peer, false);
}

void NodeImpl::check_dead_nodes(const Configuration& conf, int64_t now_ms) {
void NodeImpl::check_dead_nodes(const Configuration& conf, int64_t now_ms,
Configuration &alive_nodes) {
std::vector<PeerId> peers;
conf.list_peers(&peers);
size_t alive_count = 0;
alive_nodes.reset();
Configuration dead_nodes; // for easily print
for (size_t i = 0; i < peers.size(); i++) {
if (peers[i] == _server_id) {
++alive_count;
alive_nodes.add_peer(peers[i]);
continue;
}

if (now_ms - _replicator_group.last_rpc_send_timestamp(peers[i])
<= _options.election_timeout_ms) {
++alive_count;
alive_nodes.add_peer(peers[i]);
continue;
}
dead_nodes.add_peer(peers[i]);
}
if (alive_count >= peers.size() / 2 + 1) {
if (alive_nodes.size() >= peers.size() / 2 + 1) {
return;
}
LOG(WARNING) << "node " << node_id()
Expand All @@ -802,6 +805,71 @@ void NodeImpl::check_dead_nodes(const Configuration& conf, int64_t now_ms) {
step_down(_current_term, false, status);
}

bool NodeImpl::check_degraded(const Configuration &conf,
const Configuration &alive_nodes) {
std::vector<PeerId> peers;
alive_nodes.list_peers(&peers);
std::vector<PeerId> alive_non_arbiters;
for (size_t i = 0; i < peers.size(); i++) {
if (peers[i] == _server_id || !_replicator_group.arbiter(peers[i])) {
alive_non_arbiters.push_back(peers[i]);
}
}

if (alive_non_arbiters.size() < conf.size() / 2 + 1) {
LOG(WARNING) << "node " << node_id()
<< " term " << _current_term
<< " alive non-arbiter node don't satisfy quorm"
<< " for conf: " << conf
<< " alive nodes: " << alive_nodes
<< " alive non-arbiter nodes: " << Configuration(alive_non_arbiters);
return true;
}

// not in degraded mode, skip further check
if (!_degraded) {
return false;
}

// exit degraded mode if majority already caught up
Configuration caughtup_nodes;
for (size_t i = 0 ; i < alive_non_arbiters.size(); i++) {
if (alive_non_arbiters[i] == _server_id ||
_replicator_group.is_caughtup(alive_non_arbiters[i], _options.catchup_margin)) {
caughtup_nodes.add_peer(alive_non_arbiters[i]);
}
}
LOG(WARNING) << "node " << node_id()
<< " term " << _current_term
<< " in degraded mode and alive non-arbiter node satisfy quorm"
<< " for conf: " << conf
<< " alive nodes: " << alive_nodes
<< " alive non-arbiter nodes: " << Configuration(alive_non_arbiters)
<< " alive non-arbiter caught up nodes: " << caughtup_nodes;
return caughtup_nodes.size() < conf.size() / 2 + 1;
}

void NodeImpl::enter_degraded_mode() {
if (!_degraded) {
LOG(WARNING) << "node " << node_id()
<< " term " << _current_term
<< " enter degraded mode"
<< " last_committed_index " << _ballot_box->last_committed_index();
_degraded = true;
_replicator_group.enter_degraded_mode();
}
}

void NodeImpl::exit_degraded_mode() {
if (_degraded) {
LOG(WARNING) << "node " << node_id()
<< " term " << _current_term
<< " exit degraded mode";
_degraded = false;
_replicator_group.exit_degraded_mode();
}
}

void NodeImpl::handle_stepdown_timeout() {
BAIDU_SCOPED_LOCK(_mutex);

Expand All @@ -814,9 +882,25 @@ void NodeImpl::handle_stepdown_timeout() {
}

int64_t now = butil::monotonic_time_ms();
check_dead_nodes(_conf.conf, now);
Configuration alive_nodes, old_alive_nodes;
check_dead_nodes(_conf.conf, now, alive_nodes);
if (!_conf.old_conf.empty()) {
check_dead_nodes(_conf.old_conf, now, old_alive_nodes);
}

if (_state != STATE_LEADER) {
return;
}

bool degraded = check_degraded(_conf.conf, alive_nodes);
if (!_conf.old_conf.empty()) {
check_dead_nodes(_conf.old_conf, now);
degraded |= check_degraded(_conf.old_conf, old_alive_nodes);
}

if (!degraded) {
exit_degraded_mode();
} else {
enter_degraded_mode();
}
}

Expand Down Expand Up @@ -1053,6 +1137,12 @@ void NodeImpl::handle_election_timeout() {
_leader_id.to_string().c_str());
reset_leader_id(empty_id, status);

if (arbiter()) {
BRAFT_VLOG << "arbiter node " << _group_id << ":" << _server_id
<< " lost connection from leader";
return;
}

return pre_vote(&lck, triggered);
// Don't touch any thing of *this ever after
}
Expand Down Expand Up @@ -1090,6 +1180,16 @@ void NodeImpl::handle_timeout_now_request(brpc::Controller* controller,
<< state2str(saved_state) << " at term=" << saved_term;
return;
}
if (arbiter()) {
const int64_t saved_term = _current_term;
response->set_term(_current_term);
response->set_success(false);
lck.unlock();
LOG(WARNING) << "arbiter node " << _group_id << ":" << _server_id
<< " received handle_timeout_now_request "
<< " at term=" << saved_term;
return;
}
const butil::EndPoint remote_side = controller->remote_side();
const int64_t saved_term = _current_term;
if (FLAGS_raft_enable_leader_lease) {
Expand Down Expand Up @@ -1201,6 +1301,12 @@ int NodeImpl::transfer_leadership_to(const PeerId& peer) {
<< " which doesn't belong to " << _conf.conf;
return EINVAL;
}
if (_replicator_group.arbiter(peer_id)) {
LOG(INFO) << "node " << _group_id << ":" << _server_id
<< " refused to transfer leadership to peer "
<< peer_id << " which is arbiter";
return EINVAL;
}
const int64_t last_log_index = _log_manager->last_log_index();
const int rc = _replicator_group.transfer_leadership_to(peer_id, last_log_index);
if (rc != 0) {
Expand All @@ -1211,6 +1317,9 @@ int NodeImpl::transfer_leadership_to(const PeerId& peer) {
LOG(WARNING) << "node " << _group_id << ":" << _server_id
<< " fail to transfer leadership, peer=" << peer_id
<< " whose consecutive_error_times not 0.";
} else if (rc == ENODATA) {
LOG(WARNING) << "node " << _group_id << ":" << _server_id
<< " fail to transfer leadership, peer " << peer_id << " is arbiter";
} else {
LOG(WARNING) << "node " << _group_id << ":" << _server_id
<< " fail to transfer leadership, peer=" << peer_id
Expand Down Expand Up @@ -1243,6 +1352,9 @@ butil::Status NodeImpl::vote(int election_timeout_ms) {
if (_state != STATE_FOLLOWER) {
return butil::Status(EPERM, "is not follower");
}
if (arbiter()) {
return butil::Status(EPERM, "is arbiter");
}
int max_election_timeout_ms = _options.max_clock_drift_ms + _options.election_timeout_ms;
if (election_timeout_ms > max_election_timeout_ms) {
return butil::Status(EINVAL, "election_timeout_ms larger than safety threshold");
Expand Down Expand Up @@ -1789,6 +1901,7 @@ void NodeImpl::step_down(const int64_t term, bool wakeup_a_candidate,
// _conf_ctx.reset() will stop replicators of catching up nodes
_conf_ctx.reset();
_majority_nodes_readonly = false;
_degraded = false;

clear_append_entries_cache();

Expand Down Expand Up @@ -2478,6 +2591,7 @@ void NodeImpl::handle_append_entries_request(brpc::Controller* cntl,
response->set_term(_current_term);
response->set_last_log_index(_log_manager->last_log_index());
response->set_readonly(_node_readonly);
response->set_arbiter(arbiter());
lck.unlock();
// see the comments at FollowerStableClosure::run()
_ballot_box->set_last_committed_index(
Expand Down Expand Up @@ -2701,10 +2815,12 @@ void NodeImpl::describe(std::ostream& os, bool use_html) {
_replicator_group.list_replicators(&replicators);
const int64_t leader_timestamp = _follower_lease.last_leader_timestamp();
const bool readonly = (_node_readonly || _majority_nodes_readonly);
const bool degraded = _degraded;
lck.unlock();
const char *newline = use_html ? "<br>" : "\r\n";
os << "peer_id: " << _server_id << newline;
os << "state: " << state2str(st) << newline;
os << "arbiter: " << arbiter() << newline;
os << "readonly: " << readonly << newline;
os << "term: " << term << newline;
os << "conf_index: " << conf_index << newline;
Expand All @@ -2725,7 +2841,8 @@ void NodeImpl::describe(std::ostream& os, bool use_html) {
// info of configuration change
if (st == STATE_LEADER) {
os << "changing_conf: " << is_changing_conf
<< " stage: " << conf_statge << newline;
<< " stage: " << conf_statge << newline
<< "degraded: " << degraded << newline;
}
if (!new_peers.empty()) {
os << "new_peers:";
Expand Down Expand Up @@ -3578,6 +3695,11 @@ int64_t NodeImpl::last_leader_active_timestamp() {
return timestamp;
}

bool NodeImpl::degraded() {
BAIDU_SCOPED_LOCK(_mutex);
return _degraded;
}

struct LastActiveTimestampCompare {
bool operator()(const int64_t& a, const int64_t& b) {
return a > b;
Expand Down
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