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raft: inline raft::log::truncate_tail()

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It's the core of apply_snapshot() work and is only used in it.

Now that truncate_tail is inline, rename truncate_head()
to truncate_uncommitted().
This commit is contained in:
Konstantin Osipov
2021-02-16 23:10:58 +03:00
parent e0011c6e4d
commit cfe407b402
2 changed files with 30 additions and 35 deletions
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62
raft/log.cc
View File

@@ -61,7 +61,7 @@ index_t log::next_idx() const {
return last_idx() + index_t(1);
}
void log::truncate_head(index_t idx) {
void log::truncate_uncommitted(index_t idx) {
assert(idx >= _first_idx);
auto it = _log.begin() + (idx - _first_idx);
_log.erase(it, _log.end());
@@ -76,35 +76,6 @@ void log::truncate_head(index_t idx) {
}
}
size_t log::truncate_tail(index_t idx, size_t trailing) {
size_t removed;
if (idx > last_idx()) {
// Remove all entries ignoring the 'trailing' argument,
// since otherwise there would be a gap between old
// entries and the next entry index.
removed = _log.size();
_log.clear();
_first_idx = idx + index_t{1};
} else {
removed = _log.size() - (last_idx() - idx);
removed -= std::min(trailing, removed);
_log.erase(_log.begin(), _log.begin() + removed);
_first_idx = _first_idx + index_t{removed};
}
_stable_idx = std::max(idx, _stable_idx);
if (_first_idx > _prev_conf_idx) {
_prev_conf_idx = index_t{0};
if (_first_idx > _last_conf_idx) {
_last_conf_idx = index_t{0};
}
}
return removed;
}
void log::init_last_conf_idx() {
for (auto it = _log.rbegin(); it != _log.rend(); ++it) {
if (std::holds_alternative<configuration>((**it).data)) {
@@ -193,7 +164,7 @@ index_t log::maybe_append(std::vector<log_entry_ptr>&& entries) {
// If an existing entry conflicts with a new one (same
// index but different terms), delete the existing
// entry and all that follow it (§5.3).
truncate_head(e->idx);
truncate_uncommitted(e->idx);
}
// Assert log monotonicity
assert(e->idx == next_idx());
@@ -206,10 +177,35 @@ index_t log::maybe_append(std::vector<log_entry_ptr>&& entries) {
size_t log::apply_snapshot(snapshot&& snp, size_t trailing) {
assert (snp.idx >= _first_idx);
size_t ret = truncate_tail(snp.idx, trailing);
size_t removed;
auto idx = snp.idx;
if (idx > last_idx()) {
// Remove all entries ignoring the 'trailing' argument,
// since otherwise there would be a gap between old
// entries and the next entry index.
removed = _log.size();
_log.clear();
_first_idx = idx + index_t{1};
} else {
removed = _log.size() - (last_idx() - idx);
removed -= std::min(trailing, removed);
_log.erase(_log.begin(), _log.begin() + removed);
_first_idx = _first_idx + index_t{removed};
}
_stable_idx = std::max(idx, _stable_idx);
if (_first_idx > _prev_conf_idx) {
_prev_conf_idx = index_t{0};
if (_first_idx > _last_conf_idx) {
_last_conf_idx = index_t{0};
}
}
_snapshot = std::move(snp);
return ret;
return removed;
}
std::ostream& operator<<(std::ostream& os, const log& l) {

3
raft/log.hh
View File

@@ -72,8 +72,7 @@ class log {
index_t _prev_conf_idx = index_t{0};
private:
// Drop uncommitted log entries not present on the leader.
void truncate_head(index_t i);
size_t truncate_tail(index_t idx, size_t trailing);
void truncate_uncommitted(index_t i);
// A helper used to find the last configuration entry in the
// log after it's been loaded from disk.
void init_last_conf_idx();