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Add Start/Stop methods to RaftServer

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Summary:
Explicitly start and stop raft server.
This way we can be sure that raft won't try to use coordination after it's
shutdown, and we can define the start of th raft protocol easier.

Reviewers: ipaljak

Reviewed By: ipaljak

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1766
This commit is contained in:
Matija Santl 2018-12-11 10:51:37 +01:00
parent 8e796e9fd1
commit 8e35d8afdc
3 changed files with 35 additions and 22 deletions
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6
src/database/single_node_ha/graph_db.cpp
View File

@ -19,6 +19,7 @@ GraphDb::GraphDb(Config config) : config_(config) {}
void GraphDb::Start() {
utils::CheckDir(config_.durability_directory);
raft_server_.Start();
CHECK(coordination_.Start()) << "Couldn't start coordination!";
// Start transaction killer.
@ -62,7 +63,10 @@ bool GraphDb::AwaitShutdown(std::function<void(void)> call_before_shutdown) {
return ret;
}
void GraphDb::Shutdown() { coordination_.Shutdown(); }
void GraphDb::Shutdown() {
raft_server_.Shutdown();
coordination_.Shutdown();
}
std::unique_ptr<GraphDbAccessor> GraphDb::Access() {
// NOTE: We are doing a heap allocation to allow polymorphism. If this poses

27
src/raft/raft_server.cpp
View File

@ -27,7 +27,9 @@ RaftServer::RaftServer(uint16_t server_id, const std::string &durability_dir,
mode_(Mode::FOLLOWER),
server_id_(server_id),
disk_storage_(fs::path(durability_dir) / kRaftDir),
reset_callback_(reset_callback) {
reset_callback_(reset_callback) {}
void RaftServer::Start() {
// Persistent storage initialization/recovery.
if (Log().empty()) {
UpdateTerm(0);
@ -36,14 +38,14 @@ RaftServer::RaftServer(uint16_t server_id, const std::string &durability_dir,
}
// Peer state
int cluster_size = coordination_->WorkerCount();
int cluster_size = coordination_->WorkerCount() + 1;
next_index_.resize(cluster_size);
match_index_.resize(cluster_size);
next_heartbeat_.resize(cluster_size);
backoff_until_.resize(cluster_size);
// RPC registration
coordination->Register<RequestVoteRpc>(
coordination_->Register<RequestVoteRpc>(
[this](const auto &req_reader, auto *res_builder) {
std::lock_guard<std::mutex> guard(lock_);
RequestVoteReq req;
@ -64,8 +66,7 @@ RaftServer::RaftServer(uint16_t server_id, const std::string &durability_dir,
// set currentTerm = T and convert to follower.
if (req.term > current_term) {
UpdateTerm(req.term);
if (mode_ != Mode::FOLLOWER)
Transition(Mode::FOLLOWER);
if (mode_ != Mode::FOLLOWER) Transition(Mode::FOLLOWER);
}
// [Raft paper 5.2, 5.4]
@ -105,8 +106,7 @@ RaftServer::RaftServer(uint16_t server_id, const std::string &durability_dir,
// set currentTerm = T and convert to follower.
if (req.term > current_term) {
UpdateTerm(req.term);
if (mode_ != Mode::FOLLOWER)
Transition(Mode::FOLLOWER);
if (mode_ != Mode::FOLLOWER) Transition(Mode::FOLLOWER);
}
// respond positively to a heartbeat.
@ -162,11 +162,14 @@ RaftServer::RaftServer(uint16_t server_id, const std::string &durability_dir,
}
}
RaftServer::~RaftServer() {
exiting_ = true;
void RaftServer::Shutdown() {
{
std::lock_guard<std::mutex> guard(lock_);
exiting_ = true;
state_changed_.notify_all();
election_change_.notify_all();
state_changed_.notify_all();
election_change_.notify_all();
}
for (auto &peer_thread : peer_threads_) {
if (peer_thread.joinable()) peer_thread.join();
@ -449,6 +452,8 @@ void RaftServer::PeerThreadMain(int peer_id) {
});
next_heartbeat_[peer_id] =
Clock::now() + config_.heartbeat_interval;
state_changed_.notify_all();
continue;
}
wait_until = next_heartbeat_[peer_id];
break;

24
src/raft/raft_server.hpp
View File

@ -18,7 +18,7 @@
namespace raft {
using Clock = std::chrono::system_clock;
using Clock = std::chrono::system_clock;
using TimePoint = std::chrono::system_clock::time_point;
enum class Mode { FOLLOWER, CANDIDATE, LEADER };
@ -55,7 +55,11 @@ class RaftServer final : public RaftInterface {
const Config &config, raft::Coordination *coordination,
std::function<void(void)> reset_callback);
~RaftServer();
/// Starts the RPC servers and starts mechanisms inside Raft protocol.
void Start();
/// Stops all threads responsible for the Raft protocol.
void Shutdown();
/// Retrieves the current term from persistent storage.
///
@ -117,7 +121,7 @@ class RaftServer final : public RaftInterface {
bool IsStateDeltaTransactionEnd(const database::StateDelta &delta);
};
mutable std::mutex lock_; ///< Guards all internal state.
mutable std::mutex lock_; ///< Guards all internal state.
//////////////////////////////////////////////////////////////////////////////
// volatile state on all servers
@ -138,13 +142,13 @@ class RaftServer final : public RaftInterface {
/// log is ready for replication it will be discarded anyway.
LogEntryBuffer log_entry_buffer_{this};
std::vector<std::thread> peer_threads_; ///< One thread per peer which
///< handles outgoing RPCs.
std::vector<std::thread> peer_threads_; ///< One thread per peer which
///< handles outgoing RPCs.
std::condition_variable state_changed_; ///< Notifies all peer threads on
///< relevant state change.
std::condition_variable state_changed_; ///< Notifies all peer threads on
///< relevant state change.
bool exiting_ = false; ///< True on server shutdown.
bool exiting_ = false; ///< True on server shutdown.
//////////////////////////////////////////////////////////////////////////////
// volatile state on followers and candidates
@ -153,8 +157,8 @@ class RaftServer final : public RaftInterface {
std::thread election_thread_; ///< Timer thread for triggering elections.
TimePoint next_election_; ///< Next election `TimePoint`.
std::condition_variable election_change_; ///> Used to notify election_thread
///> on next_election_ change.
std::condition_variable election_change_; ///> Used to notify election_thread
///> on next_election_ change.
std::mt19937_64 rng_ = std::mt19937_64(std::random_device{}());