feat(config): add txn_context_enabled to allow to enable the transa…

…ction feature (apache#2506)

Co-authored-by: mwish <maplewish117@gmail.com>

kvrocks.conf

@@ -335,6 +335,20 @@ json-max-nesting-depth 1024
 # Default: json
 json-storage-format json
 
+# Whether to enable transactional mode engine::Context.
+#
+# If enabled, is_txn_mode in engine::Context will be set properly,
+# which is expected to improve the consistency of commands.
+# If disabled, is_txn_mode in engine::Context will be set to false,
+# making engine::Context equivalent to engine::Storage.
+#
+# NOTE: This is an experimental feature. If you find errors, performance degradation,
+# excessive memory usage, excessive disk I/O, etc. after enabling it, please try disabling it.
+# At the same time, we welcome feedback on related issues to help iterative improvements.
+# 
+# Default: no
+txn-context-enabled no
+
 ################################## TLS ###################################
 
 # By default, TLS/SSL is disabled, i.e. `tls-port` is set to 0.

src/config/config.cc

@@ -193,6 +193,7 @@ Config::Config() {
       {"json-max-nesting-depth", false, new IntField(&json_max_nesting_depth, 1024, 0, INT_MAX)},
       {"json-storage-format", false,
        new EnumField<JsonStorageFormat>(&json_storage_format, json_storage_formats, JsonStorageFormat::JSON)},
+      {"txn-context-enabled", true, new YesNoField(&txn_context_enabled, false)},
 
       /* rocksdb options */
       {"rocksdb.compression", false,

src/config/config.h

@@ -168,6 +168,9 @@ struct Config {
   int json_max_nesting_depth = 1024;
   JsonStorageFormat json_storage_format = JsonStorageFormat::JSON;
 
+  // Enable transactional mode in engine::Context
+  bool txn_context_enabled = false;
+
   struct RocksDB {
     int block_size;
     bool cache_index_and_filter_blocks;

src/storage/storage.h

@@ -388,7 +388,8 @@ struct Context {
   std::unique_ptr<rocksdb::WriteBatchWithIndex> batch = nullptr;
 
   /// is_txn_mode is used to determine whether the current Context is in transactional mode,
-  /// if it is not transactional mode, then Context is equivalent to a Storage
+  /// if it is not transactional mode, then Context is equivalent to a Storage.
+  /// If the configuration of txn-context-enabled is no, it is false.
   bool is_txn_mode = true;
 
   /// NoTransactionContext returns a Context with a is_txn_mode of false
@@ -409,6 +410,10 @@ struct Context {
   /// TODO: Change it to defer getting the context, and the snapshot is pinned after the first read operation
   explicit Context(engine::Storage *storage) : storage(storage) {
     auto guard = storage->ReadLockGuard();
+    if (!storage->GetConfig()->txn_context_enabled) {
+      is_txn_mode = false;
+      return;
+    }
     snapshot = storage->GetDB()->GetSnapshot();  // NOLINT
   }
   ~Context() {