address a race described in project-tsurugi/tsurugi-issues#1034 (comm…

…ent)
project-tsurugi · Nov 28, 2024 · 77552d6 · 77552d6
1 parent f8ad37d
commit 77552d6
Show file tree

Hide file tree

Showing 2 changed files with 15 additions and 8 deletions.
diff --git a/include/limestone/api/datastore.h b/include/limestone/api/datastore.h
@@ -249,7 +249,7 @@ class datastore {
 protected:  // for tests
     auto& log_channels_for_tests() const noexcept { return log_channels_; }
     auto epoch_id_informed_for_tests() const noexcept { return epoch_id_informed_.load(); }
-    auto epoch_id_recorded_for_tests() const noexcept { return epoch_id_recorded_.load(); }
+    auto epoch_id_recorded_for_tests() const noexcept { return epoch_id_to_be_recorded_.load(); }
     auto epoch_id_switched_for_tests() const noexcept { return epoch_id_switched_.load(); }
     auto& files_for_tests() const noexcept { return files_; }
     void rotate_epoch_file_for_tests() { rotate_epoch_file(); }
@@ -263,7 +263,8 @@ class datastore {
 
     std::atomic_uint64_t epoch_id_informed_{};
 
-    std::atomic_uint64_t epoch_id_recorded_{};
+    std::atomic_uint64_t epoch_id_to_be_recorded_{};
+    std::atomic_uint64_t epoch_id_record_finished_{};
 
     std::unique_ptr<backup> backup_{};
 

diff --git a/src/limestone/datastore.cpp b/src/limestone/datastore.cpp
@@ -162,7 +162,9 @@ void datastore::switch_epoch(epoch_id_type new_epoch_id) {
         }
 
         epoch_id_switched_.store(neid);
-        update_min_epoch_id(true);
+        if (state_ != state::not_ready) {
+            update_min_epoch_id(true);
+        }
     } catch (...) {
         HANDLE_EXCEPTION_AND_ABORT();
     }
@@ -171,7 +173,7 @@ void datastore::switch_epoch(epoch_id_type new_epoch_id) {
 void datastore::update_min_epoch_id(bool from_switch_epoch) {  // NOLINT(readability-function-cognitive-complexity)
     auto upper_limit = epoch_id_switched_.load();
     if (upper_limit == 0) {
-        return; // If epoch_id_switched_ is zero, it means no epoch has been switched, so updating epoch_id_recorded_ and epoch_id_informed_ is unnecessary.
+        return; // If epoch_id_switched_ is zero, it means no epoch has been switched, so updating epoch_id_to_be_recorded_ and epoch_id_informed_ is unnecessary.
     }
     upper_limit--;
     epoch_id_type max_finished_epoch = 0;
@@ -194,21 +196,21 @@ void datastore::update_min_epoch_id(bool from_switch_epoch) {  // NOLINT(readabi
     if (from_switch_epoch && (to_be_epoch > static_cast<std::uint64_t>(max_finished_epoch))) {
         to_be_epoch = static_cast<std::uint64_t>(max_finished_epoch);
     }
-    auto old_epoch_id = epoch_id_recorded_.load();
+    auto old_epoch_id = epoch_id_to_be_recorded_.load();
     while (true) {
         if (old_epoch_id >= to_be_epoch) {
             break;
         }
-        if (epoch_id_recorded_.compare_exchange_strong(old_epoch_id, to_be_epoch)) {
+        if (epoch_id_to_be_recorded_.compare_exchange_strong(old_epoch_id, to_be_epoch)) {
             std::lock_guard<std::mutex> lock(mtx_epoch_file_);
-            if (to_be_epoch < epoch_id_recorded_.load()) {
+            if (to_be_epoch < epoch_id_to_be_recorded_.load()) {
                 break;
             }
             FILE* strm = fopen(epoch_file_path_.c_str(), "a");  // NOLINT(*-owning-memory)
             if (!strm) {
                 LOG_AND_THROW_IO_EXCEPTION("fopen failed", errno);
             }
-            log_entry::durable_epoch(strm, static_cast<epoch_id_type>(epoch_id_recorded_.load()));
+            log_entry::durable_epoch(strm, static_cast<epoch_id_type>(epoch_id_to_be_recorded_.load()));
             if (fflush(strm) != 0) {
                 LOG_AND_THROW_IO_EXCEPTION("fflush failed", errno);
             }
@@ -218,9 +220,13 @@ void datastore::update_min_epoch_id(bool from_switch_epoch) {  // NOLINT(readabi
             if (fclose(strm) != 0) {  // NOLINT(*-owning-memory)
                 LOG_AND_THROW_IO_EXCEPTION("fclose failed", errno);
             }
+            epoch_id_record_finished_.store(epoch_id_to_be_recorded_.load());
             break;
         }
     }
+    if (to_be_epoch > epoch_id_record_finished_.load()) {
+        return;
+    }
 
     // update informed_epoch_
     to_be_epoch = upper_limit;