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Keep last raft log entry metadata in memory

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Reviewers: msantl, mferencevic

Reviewed By: msantl

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D2096
This commit is contained in:
Ivan Paljak 2019-05-28 17:27:06 +02:00
parent f6264ab2ae
commit c21d04ce8d
2 changed files with 15 additions and 16 deletions

25
src/raft/raft_server.cpp
View File

@ -48,6 +48,7 @@ RaftServer::RaftServer(uint16_t server_id, const std::string &durability_dir,
db_recover_on_startup_(db_recover_on_startup),
commit_index_(0),
last_applied_(0),
last_entry_term_(0),
issue_hb_(false),
replication_timeout_(config.replication_timeout),
disk_storage_(fs::path(durability_dir) / kRaftDir) {}
@ -59,6 +60,7 @@ void RaftServer::Start() {
RecoverSnapshot(snapshot_metadata_->snapshot_filename);
last_applied_ = snapshot_metadata_->last_included_index;
commit_index_ = snapshot_metadata_->last_included_index;
last_entry_term_ = snapshot_metadata_->last_included_term;
}
} else {
// We need to clear persisted data if we don't want any recovery.
@ -439,6 +441,7 @@ void RaftServer::AppendToLog(const tx::TransactionId &tx_id,
log_[log_size_] = new_entry;
disk_storage_.Put(LogEntryKey(log_size_), SerializeLogEntry(new_entry));
last_entry_term_ = new_entry.term;
SetLogSize(log_size_ + 1);
// Force replication
@ -560,6 +563,14 @@ void RaftServer::RecoverPersistentData() {
auto opt_log_size = disk_storage_.Get(kLogSizeKey);
if (opt_log_size) log_size_ = std::stoull(opt_log_size.value());
if (log_size_ != 0) {
auto opt_last_log_entry = disk_storage_.Get(LogEntryKey(log_size_ - 1));
DCHECK(opt_last_log_entry != std::nullopt)
<< "Log size is equal to " << log_size_
<< ", but there is no log entry on index: " << log_size_ - 1;
last_entry_term_ = DeserializeLogEntry(opt_last_log_entry.value()).term;
}
}
void RaftServer::Transition(const Mode &new_mode) {
@ -1159,7 +1170,7 @@ std::pair<uint64_t, uint64_t> RaftServer::LastEntryData() {
snapshot_metadata_->last_included_index == log_size_ - 1) {
return {log_size_, snapshot_metadata_->last_included_term};
}
return {log_size_, GetLogEntryTerm(log_size_ - 1)};
return {log_size_, last_entry_term_};
}
bool RaftServer::AtLeastUpToDate(uint64_t last_log_index_a,
@ -1200,16 +1211,6 @@ LogEntry RaftServer::GetLogEntry(int index) {
return DeserializeLogEntry(opt_value.value());
}
uint64_t RaftServer::GetLogEntryTerm(int index) {
auto it = log_.find(index);
if (it != log_.end())
return it->second.term; // retrieve in-mem if possible
auto opt_value = disk_storage_.Get(LogEntryKey(index));
DCHECK(opt_value != std::nullopt)
<< "Log index (" << index << ") out of bounds.";
return DeserializeLogEntry(opt_value.value()).term;
}
void RaftServer::DeleteLogSuffix(int starting_index) {
DCHECK(0 <= starting_index && starting_index < log_size_)
<< "Log index out of bounds.";
@ -1252,6 +1253,8 @@ void RaftServer::AppendLogEntries(uint64_t leader_commit_index,
if (leader_commit_index > commit_index_) {
commit_index_ = std::min(leader_commit_index, log_size_ - 1);
}
last_entry_term_ = GetLogEntry(log_size_ - 1).term;
}
std::string RaftServer::LogEntryKey(uint64_t index) {

6
src/raft/raft_server.hpp
View File

@ -183,6 +183,7 @@ class RaftServer final : public RaftInterface {
///< on startup.
uint64_t commit_index_; ///< Index of the highest known committed entry.
uint64_t last_applied_; ///< Index of the highest applied entry to SM.
uint64_t last_entry_term_; ///< Term of the last entry in Raft log
std::atomic<bool> issue_hb_; ///< Flag which signalizes if the current server
///< should send HBs to the rest of the cluster.
@ -399,11 +400,6 @@ class RaftServer final : public RaftInterface {
/// @param index Index of the log entry to be retrieved.
LogEntry GetLogEntry(int index);
/// Retrieves the term of a log entry from the log at a given index.
///
/// @param index Index of the log entry whose term is to be retrieved.
uint64_t GetLogEntryTerm(int index);
/// Deletes log entries with indexes that are greater or equal to the given
/// starting index.
///