Initialize to prevent borrowing nullptr's

Author: serbel324

.github/config/muted_ya.txt

@@ -4,7 +4,6 @@ ydb/core/client/ut TClientTest.PromoteFollower
 ydb/core/client/ut TClientTest.ReadFromFollower
 ydb/core/client/ut TFlatTest.AutoSplitMergeQueue
 ydb/core/cms/ut_sentinel TSentinelTests.BSControllerCantChangeStatus
-ydb/core/debug_tools/ut OperationLog.ConcurrentWrites
 ydb/core/quoter/ut QuoterWithKesusTest.PrefetchCoefficient
 ydb/core/kafka_proxy/ut KafkaProtocol.CreatePartitionsScenario
 ydb/core/kafka_proxy/ut KafkaProtocol.ProduceScenario

ydb/core/debug_tools/operation_log.h

@@ -27,11 +27,16 @@ class TOperationLog {
 private:
     constexpr static ui32 Capacity = S;
     std::array<std::atomic<TString*>, S> Records;
-    // RecordIdx is shifted to prevent underflow on decrement
+    // RecordPosition is shifted to prevent underflow on decrement
     std::atomic<ui64> NextRecordPosition = Capacity;
+    std::atomic<ui64> CommittedRecordPosition = Capacity;
 
 public:
-    TOperationLog() = default;
+    TOperationLog(bool initializeRecords = true, TString defaultValue = "Race occured, try again") {
+        if (initializeRecords) {
+            InitializeRecords(defaultValue);
+        }
+    };
 
     TOperationLog(const TOperationLog& other) = delete;
     TOperationLog& operator=(const TOperationLog& other) = delete;
@@ -45,6 +50,12 @@ class TOperationLog {
         }
     }
 
+    bool InitializeRecords(TString value = "Race occured, try again") {
+        for (auto& record : Records) {
+            record.store(new TString(value))
+        }
+    }
+
     BorrowedRecord BorrowByIdx(ui32 idx) {
         ui32 position = (NextRecordPosition.load() - 1 - idx) % Capacity;
         if (idx >= Size()) {
@@ -68,11 +79,12 @@ class TOperationLog {
     }
 
     ui32 Size() const {
-        return Min(NextRecordPosition.load() - Capacity, static_cast<ui64>(Capacity));
+        return Min(CommittedRecordPosition.load() - Capacity, static_cast<ui64>(Capacity));
     }
 
     void AddRecord(std::unique_ptr<TString>& value) {
         TString* prev = Records[NextRecordPosition.fetch_add(1) % Capacity].exchange(value.release());
+        CommittedRecordPosition.fetch_add(1);
         if (prev) {
             delete prev;
         }