placeholder for mds data source type and related mds ctx

Co-authored-by: fengdeyiji <546976189@qq.com>

src/storage/CMakeLists.txt

@@ -677,6 +677,9 @@ ob_set_subtarget(ob_storage multi_data_source
   multi_data_source/ob_mds_table_merge_dag.cpp
   multi_data_source/ob_mds_table_merge_dag_param.cpp
   multi_data_source/ob_mds_table_merge_task.cpp
+  multi_data_source/ob_start_transfer_in_mds_ctx.cpp
+  multi_data_source/ob_finish_transfer_in_mds_ctx.cpp
+  multi_data_source/ob_tablet_create_mds_ctx.cpp
   multi_data_source/test/example_user_helper_define.cpp
 )
 

src/storage/multi_data_source/compile_utility/mds_register.h

@@ -10,6 +10,40 @@
  * See the Mulan PubL v2 for more details.
  */
 
+// ################################### 使用多源事务兼容性占位须知 ##################################
+// # 占位代码需要书写于宏定义块【NEED_GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION】中
+// # 占位方式: 通过【注释】占位，占位需要信息：Helper类型名/Ctx类型名/Enum数值/Enum命名
+// #
+// # 注意：
+// # 0. 在‘余留位置’之前占位
+// # 1. 始终先在master占位，保证master分支是其他所有分支的超集
+// # 2. master占位之后，开发分支上不可修改注册宏中的对应信息，否则FARM会认为占位冲突，如果有这种场景，需要先修改master占位
+// # 3. 所有类型名的书写从全局命名空间'::oceanbase'开始
+// # 4. Enum数值采用递增方式占位
+// # 5. Enum命名不可同前文重复
+// # 6. 由于采用注释方式占位，因此【不需要】书写对应的类型定义并包含在【NEED_MDS_REGISTER_DEFINE】中
+// ############################################################################################
+
+// ################################### 使用多源数据兼容性占位须知 ##################################
+// # 占位代码需要书写于宏定义块【GENERATE_MDS_UNIT】中，更近一步的:
+// # 1. 如果想要添加tablet级别元数据，则将占位信息增加至【GENERATE_NORMAL_MDS_TABLE】中
+// # 2. 如果想要添加日志流级别元数据，则将占位信息增加至【GENERATE_LS_INNER_MDS_TABLE】中
+// # 占位方式: 通过【定义】占位，占位需要信息：Key类型名/Value类型名/多版本语义支持
+// #
+// # 注意：
+// # 0. 在‘余留位置’之前占位
+// # 1. 始终先在master占位，保证master分支是其他所有分支的超集
+// # 2. master占位之后，开发分支上不可修改注册宏中的对应信息，否则FARM会认为占位冲突，如果有这种场景，需要先修改master占位
+// # 3. 所有类型名的书写从全局命名空间'::oceanbase'开始
+// # 4. 若Key类型名非'::oceanbase::storage::mds::DummyKey'，则需要提供对应的Key类型定义，并将对应头文件包含在【NEED_MDS_REGISTER_DEFINE】中
+// # 5. 需要提供对应的Value类型定义，并将对应头文件包含在【NEED_MDS_REGISTER_DEFINE】中
+// # 6. Key/Value的类型仅需要空定义，不需要定义成员方法和变量，但需要实现框架所需的接口，以通过框架的编译期检查，包括(占位时实现为空)：
+// #    a. 打印函数：[int64_t T::to_string(char *, const int64_t) const]
+// #    b. 比较函数的某种实现，例如：[bool T::operator==(const T &) const] and [bool T::operator<(const T &) const]
+// #    c. 序列化函数的某种实现，例如：[int serialize(char *, const int64_t, int64_t &) const] and [int deserialize(const char *, const int64_t, int64_t &)] and [int64_t get_serialize_size() const]
+// #    d. 拷贝/移动函数的某种实现，例如：[int T::assign(const T &)]
+// ############################################################################################
+
 // the MDS FRAME must know the defination of some class type to generate legal CPP codes, including:
 // 1. DATA type defination if you need multi source data support.
 //    1.a. KEY type defination if you need multi source data support with multi key support.
@@ -34,6 +68,9 @@
   #include "src/storage/tablet/ob_tablet_finish_transfer_mds_helper.h"
   #include "src/share/balance/ob_balance_task_table_operator.h"
   #include "src/storage/tablet/ob_tablet_transfer_tx_ctx.h"
+  #include "src/storage/multi_data_source/ob_tablet_create_mds_ctx.h"
+  #include "src/storage/multi_data_source/ob_start_transfer_in_mds_ctx.h"
+  #include "src/storage/multi_data_source/ob_finish_transfer_in_mds_ctx.h"
 #endif
 /**************************************************************************************************/
 
@@ -71,7 +108,7 @@ _GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION_(HELPER_CLASS, BUFFER_CTX_TYPE, ID, ENU
                                           16,\
                                           TEST3)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletCreateMdsHelper,\
-                                          ::oceanbase::storage::mds::MdsCtx,\
+                                          ::oceanbase::storage::mds::ObTabletCreateMdsCtx,\
                                           3,\
                                           CREATE_TABLET_NEW_MDS)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletDeleteMdsHelper,\
@@ -87,7 +124,7 @@ _GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION_(HELPER_CLASS, BUFFER_CTX_TYPE, ID, ENU
                                           20,\
                                           START_TRANSFER_OUT)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletStartTransferInHelper,\
-                                          ::oceanbase::storage::mds::MdsCtx,\
+                                          ::oceanbase::storage::mds::ObStartTransferInMdsCtx,\
                                           21,\
                                           START_TRANSFER_IN)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletFinishTransferOutHelper,\
@@ -95,7 +132,7 @@ _GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION_(HELPER_CLASS, BUFFER_CTX_TYPE, ID, ENU
                                           22,\
                                           FINISH_TRANSFER_OUT)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletFinishTransferInHelper,\
-                                          ::oceanbase::storage::mds::MdsCtx,\
+                                          ::oceanbase::storage::mds::ObFinishTransferInMdsCtx,\
                                           23,\
                                           FINISH_TRANSFER_IN)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::share::ObBalanceTaskMDSHelper,\
@@ -118,12 +155,23 @@ _GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION_(HELPER_CLASS, BUFFER_CTX_TYPE, ID, ENU
                                           ::oceanbase::storage::ObTransferDestPrepareTxCtx,\
                                           28,\
                                           TRANSFER_DEST_PREPARE)
-  // UNBIND_LOB_TABLET: ID = 29 for drop lob tablet when drop column instant.
+  // GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletUnbindLobMdsHelper,\
+  //                                         ::oceanbase::storage::mds::MdsCtx,\
+  //                                         29,\
+  //                                         UNBIND_LOB_TABLET)
   GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObChangeTabletToTableHelper,\
                                           ::oceanbase::storage::mds::MdsCtx,\
                                           30,\
                                           CHANGE_TABLET_TO_TABLE_MDS)
-  // TABLET_SPLIT: ID = 31 for auto_split.
+  // GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletSplitMdsHelper,\
+  //                                         ::oceanbase::storage::mds::MdsCtx,\
+  //                                         31,\
+  //                                         TABLET_SPLIT)
+  // GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION(::oceanbase::storage::ObTabletAbortTransferHelper,\
+  //                                         ::oceanbase::storage::mds::ObAbortTransferInMdsCtx,\
+  //                                         32,\
+  //                                         TRANSFER_IN_ABORTED)
+  // # 余留位置（此行之前占位）
 #undef GENERATE_MDS_FRAME_CODE_FOR_TRANSACTION
 #endif
 /**************************************************************************************************/
@@ -188,11 +236,13 @@ _GENERATE_MDS_UNIT_(KEY_TYPE, VALUE_TYPE, NEED_MULTI_VERSION)
   GENERATE_MDS_UNIT(::oceanbase::compaction::ObMediumCompactionInfoKey,\
                     ::oceanbase::compaction::ObMediumCompactionInfo,\
                     false)
+  // # 余留位置（此行之前占位）
 #endif
 
 #ifdef GENERATE_LS_INNER_MDS_TABLE
   GENERATE_MDS_UNIT(::oceanbase::storage::mds::DummyKey,\
                     ::oceanbase::unittest::ExampleUserData1,\
                     true) // replace this line if you are the first user to register LS INNER TABLET
+  // # 余留位置（此行之前占位）
 #endif
-/**************************************************************************************************/
+/**************************************************************************************************/

src/storage/multi_data_source/ob_finish_transfer_in_mds_ctx.cpp

@@ -0,0 +1,161 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+#include "ob_finish_transfer_in_mds_ctx.h"
+#include "lib/ob_errno.h"
+#include "lib/utility/ob_macro_utils.h"
+#include "mds_table_handle.h"
+#include "share/ob_errno.h"
+#include "storage/tx_storage/ob_ls_handle.h"
+#include "storage/tx_storage/ob_ls_service.h"
+
+#define USING_LOG_PREFIX MDS
+
+namespace oceanbase
+{
+namespace storage
+{
+namespace mds
+{
+
+ObFinishTransferInMdsCtx::ObFinishTransferInMdsCtx()
+    : MdsCtx(),
+      version_(ObFinishTransferInMdsCtxVersion::CURRENT_CTX_VERSION),
+      redo_scn_(share::SCN::base_scn())
+{
+}
+
+ObFinishTransferInMdsCtx::ObFinishTransferInMdsCtx(const MdsWriter &writer)
+    : MdsCtx(writer),
+      version_(ObFinishTransferInMdsCtxVersion::CURRENT_CTX_VERSION),
+      redo_scn_(share::SCN::base_scn())
+
+{
+}
+
+ObFinishTransferInMdsCtx::~ObFinishTransferInMdsCtx()
+{
+  version_ = ObFinishTransferInMdsCtxVersion::MAX;
+  redo_scn_.reset();
+}
+
+int ObFinishTransferInMdsCtx::serialize(char *buf, const int64_t len, int64_t &pos) const
+{
+  int ret = OB_SUCCESS;
+  int64_t saved_pos = pos;
+  const int64_t length = get_serialize_size();
+
+  if (OB_ISNULL(buf)
+      || OB_UNLIKELY(len <= 0)
+      || OB_UNLIKELY(pos < 0)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("invalid args", K(ret), K(buf), K(len), K(pos));
+  } else if (!ObFinishTransferInMdsCtxVersion::is_valid(version_)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_ERROR("invalid version", K(ret), K_(version));
+  } else if (OB_UNLIKELY(length > len - pos)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("buffer's length is not enough", K(ret), K(length), K(len - pos));
+  } else if (ObFinishTransferInMdsCtxVersion::FINISH_TRANSFER_IN_MDS_CTX_VERSION_V1 == version_) {
+    if (OB_FAIL(MdsCtx::serialize(buf, len, pos))) {
+      LOG_WARN("failed to serialize mds ctx serialize", K(ret), K(len), K(pos));
+    }
+  } else {
+    if (OB_FAIL(serialization::encode(buf, len, pos, static_cast<int64_t>(version_)))) {
+      LOG_WARN("failed to serialize tablet meta's version", K(ret), K(len), K(pos), K_(version));
+    } else if (OB_FAIL(serialization::encode_i32(buf, len, pos, length))) {
+      LOG_WARN("failed to serialize tablet meta's length", K(ret), K(len), K(pos), K(length));
+    } else if (OB_FAIL(MdsCtx::serialize(buf, len, pos))) {
+      LOG_WARN("failed to serialize mds ctx serialize", K(ret), K(len), K(pos));
+    } else if (OB_FAIL(redo_scn_.serialize(buf, len, pos))) {
+      LOG_WARN("failed to serialize redo scn", K(ret), K(len), K(pos));
+    }
+  }
+
+  if (OB_FAIL(ret)) {
+  } else if (OB_UNLIKELY(length != pos - saved_pos)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("finish transfer in mds ctx is not match standard length", K(ret), K(saved_pos), K(pos), K(length), K(len));
+  }
+
+  return ret;
+}
+
+int ObFinishTransferInMdsCtx::deserialize(const char *buf, const int64_t len, int64_t &pos)
+{
+  int ret = OB_SUCCESS;
+  int64_t saved_pos = pos;
+  int64_t version = -1;
+  int32_t length = 0;
+
+  if (OB_ISNULL(buf)
+      || OB_UNLIKELY(len <= 0)
+      || OB_UNLIKELY(pos < 0)
+      || OB_UNLIKELY(len <= pos)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("invalid args", K(ret), K(buf), K(len), K(pos));
+  } else if (OB_FAIL(serialization::decode(buf, len, pos, version))) {
+    LOG_WARN("failed to deserialize start transfer in mds ctx's version", K(ret), K(len), K(pos));
+  } else if (FALSE_IT(version_ = static_cast<ObFinishTransferInMdsCtxVersion::VERSION>(version))) {
+  } else if (ObFinishTransferInMdsCtxVersion::FINISH_TRANSFER_IN_MDS_CTX_VERSION_V1 == version_) {
+    pos = saved_pos;
+    if (OB_FAIL(MdsCtx::deserialize(buf, len, pos))) {
+      LOG_WARN("failed to deserialize mds ctx", K(ret), K(len), K(pos));
+    }
+  } else {
+    if (OB_FAIL(serialization::decode_i32(buf, len, pos, &length))) {
+      LOG_WARN("failed to deserialize start transfer in mds ctx's length", K(ret), K(len), K(pos));
+    } else if (ObFinishTransferInMdsCtxVersion::CURRENT_CTX_VERSION != version_) {
+      ret = OB_ERR_UNEXPECTED;
+      LOG_WARN("invalid version", K(ret), K_(version));
+    } else {
+      if (OB_UNLIKELY(length > len - saved_pos)) {
+        ret = OB_ERR_UNEXPECTED;
+        LOG_WARN("buffer's length is not enough", K(ret), K(length), K(len - saved_pos));
+      } else if (OB_FAIL(MdsCtx::deserialize(buf, len, pos))) {
+        LOG_WARN("failed to deserialize mds ctx", K(ret), K(len), K(pos));
+      } else if (OB_FAIL(redo_scn_.deserialize(buf, len, pos))) {
+        LOG_WARN("failed to deserialize redo scn", K(ret), K(len), K(pos));
+      } else if (OB_UNLIKELY(length != pos - saved_pos)) {
+        ret = OB_ERR_UNEXPECTED;
+        LOG_WARN("tablet's length doesn't match standard length", K(ret), K(saved_pos), K(pos), K(length), K(len));
+      }
+    }
+  }
+  return ret;
+}
+
+int64_t ObFinishTransferInMdsCtx::get_serialize_size(void) const
+{
+  int64_t size = 0;
+  const int32_t placeholder_length = 0;
+  if (ObFinishTransferInMdsCtxVersion::FINISH_TRANSFER_IN_MDS_CTX_VERSION_V1 == version_) {
+    size += MdsCtx::get_serialize_size();
+  } else {
+    const int64_t version = static_cast<int64_t>(version_);
+    size += serialization::encoded_length(version);
+    size += serialization::encoded_length_i32(placeholder_length);
+    size += MdsCtx::get_serialize_size();
+    size += redo_scn_.get_serialize_size();
+  }
+  return size;
+}
+
+void ObFinishTransferInMdsCtx::on_redo(const share::SCN &redo_scn)
+{
+  redo_scn_ = redo_scn;
+  MdsCtx::on_redo(redo_scn);
+  LOG_INFO("[TRANSFER] finish transfer in mds ctx on_redo", K(redo_scn));
+}
+
+}
+}
+}

src/storage/multi_data_source/ob_finish_transfer_in_mds_ctx.h

@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#ifndef SHARE_STORAGE_MULTI_DATA_SOURCE_OB_FINISH_TRANSFER_IN_MDS_CTX_H
+#define SHARE_STORAGE_MULTI_DATA_SOURCE_OB_FINISH_TRANSFER_IN_MDS_CTX_H
+
+#include "mds_ctx.h"
+#include "lib/container/ob_array.h"
+#include "storage/multi_data_source/runtime_utility/mds_tenant_service.h"
+#include "lib/container/ob_array_serialization.h"
+
+namespace oceanbase
+{
+namespace storage
+{
+namespace mds
+{
+class MdsTableHandle;
+struct ObFinishTransferInMdsCtxVersion
+{
+  enum VERSION {
+    FINISH_TRANSFER_IN_MDS_CTX_VERSION_V1 = 1,
+    FINISH_TRANSFER_IN_MDS_CTX_VERSION_V2 = 2,
+    MAX
+  };
+  static const VERSION CURRENT_CTX_VERSION = FINISH_TRANSFER_IN_MDS_CTX_VERSION_V2;
+  static bool is_valid(const ObFinishTransferInMdsCtxVersion::VERSION &version) {
+    return version >= FINISH_TRANSFER_IN_MDS_CTX_VERSION_V1
+        && version < MAX;
+  }
+};
+
+class ObFinishTransferInMdsCtx : public MdsCtx
+{
+public:
+  ObFinishTransferInMdsCtx();
+  ObFinishTransferInMdsCtx(const MdsWriter &writer);
+  virtual ~ObFinishTransferInMdsCtx();
+  virtual int serialize(char *buf, const int64_t len, int64_t &pos) const;
+  virtual int deserialize(const char *buf, const int64_t len, int64_t &pos);
+  virtual int64_t get_serialize_size(void) const;
+
+  virtual void on_redo(const share::SCN &redo_scn) override;
+  share::SCN &get_redo_scn() { return redo_scn_; }
+
+  INHERIT_TO_STRING_KV("MdsCtx", MdsCtx, K_(version), K_(redo_scn));
+private:
+  ObFinishTransferInMdsCtxVersion::VERSION version_;
+  share::SCN redo_scn_;
+private:
+  DISALLOW_COPY_AND_ASSIGN(ObFinishTransferInMdsCtx);
+};
+
+} //mds
+} //storage
+} //oceanbase
+
+#endif //SHARE_STORAGE_MULTI_DATA_SOURCE_OB_FINISH_TRANSFER_IN_MDS_CTX_H

src/storage/multi_data_source/ob_start_transfer_in_mds_ctx.cpp

@@ -0,0 +1,174 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+#include "ob_start_transfer_in_mds_ctx.h"
+#include "lib/ob_errno.h"
+#include "lib/utility/ob_macro_utils.h"
+#include "mds_table_handle.h"
+#include "share/ob_errno.h"
+#include "storage/tx_storage/ob_ls_handle.h"
+#include "storage/tx_storage/ob_ls_service.h"
+#include "storage/high_availability/ob_ls_transfer_info.h"
+
+#define USING_LOG_PREFIX MDS
+
+namespace oceanbase
+{
+namespace storage
+{
+namespace mds
+{
+
+//errsim def
+ERRSIM_POINT_DEF(EN_START_TRANSFER_IN_ON_PREPARE);
+
+ObStartTransferInMdsCtx::ObStartTransferInMdsCtx()
+    : MdsCtx(),
+      version_(ObStartTransferInMdsCtxVersion::CURRENT_CTX_VERSION),
+      ls_id_()
+{
+}
+
+ObStartTransferInMdsCtx::ObStartTransferInMdsCtx(const MdsWriter &writer)
+    : MdsCtx(writer),
+      version_(ObStartTransferInMdsCtxVersion::CURRENT_CTX_VERSION),
+      ls_id_()
+{
+}
+
+ObStartTransferInMdsCtx::~ObStartTransferInMdsCtx()
+{
+}
+
+void ObStartTransferInMdsCtx::on_prepare(const share::SCN &prepare_version)
+{
+  // TODO(@muwei.ym): add ERRSIM code later
+  MdsCtx::on_prepare(prepare_version);
+}
+
+void ObStartTransferInMdsCtx::on_abort(const share::SCN &abort_scn)
+{
+  mds::MdsCtx::on_abort(abort_scn);
+
+  // TODO(@bowen.gbw): feature branch transfer_dml_ctrl_42x patch to master,
+  // then add more logic, currently this code is just for compat
+}
+
+int ObStartTransferInMdsCtx::serialize(char *buf, const int64_t len, int64_t &pos) const
+{
+  int ret = OB_SUCCESS;
+  int64_t saved_pos = pos;
+  const int64_t length = get_serialize_size();
+
+  if (OB_ISNULL(buf)
+      || OB_UNLIKELY(len <= 0)
+      || OB_UNLIKELY(pos < 0)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("invalid args", K(ret), K(buf), K(len), K(pos));
+  } else if (!ObStartTransferInMdsCtxVersion::is_valid(version_)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_ERROR("invalid version", K(ret), K_(version));
+  } else if (OB_UNLIKELY(length > len - pos)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("buffer's length is not enough", K(ret), K(length), K(len - pos));
+  } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V1 == version_) {
+    if (OB_FAIL(MdsCtx::serialize(buf, len, pos))) {
+      LOG_WARN("failed to serialize mds ctx", K(ret), K(len), K(pos));
+    }
+  } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V2 == version_
+      || ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V3 == version_) {
+    if (OB_FAIL(serialization::encode(buf, len, pos, static_cast<int64_t>(version_)))) {
+      LOG_WARN("failed to serialize start transfer in mds ctx version", K(ret), K(len), K(pos), K_(version));
+    } else if (OB_FAIL(serialization::encode_i32(buf, len, pos, length))) {
+      LOG_WARN("failed to serialize start transfer in mds ctx length", K(ret), K(len), K(pos), K(length));
+    } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V3 == version_
+        && OB_FAIL(ls_id_.serialize(buf, len, pos))) {
+      LOG_WARN("failed to serialize ls id", K(ret), K(len), K(pos), K_(ls_id));
+    } else if (OB_FAIL(MdsCtx::serialize(buf, len, pos))) {
+      LOG_WARN("failed to serialize mds ctx", K(ret), K(len), K(pos));
+    }
+  }
+
+  if (OB_FAIL(ret)) {
+  } else if (OB_UNLIKELY(length != pos - saved_pos)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("start transfer in mds ctx is not match standard length", K(ret), K(saved_pos), K(pos), K(length), K(len));
+  }
+  return ret;
+}
+
+int ObStartTransferInMdsCtx::deserialize(const char *buf, const int64_t len, int64_t &pos)
+{
+  int ret = OB_SUCCESS;
+  int64_t saved_pos = pos;
+  int64_t version = -1;
+  int32_t length = 0;
+
+  if (OB_ISNULL(buf)
+      || OB_UNLIKELY(len <= 0)
+      || OB_UNLIKELY(pos < 0)
+      || OB_UNLIKELY(len <= pos)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("invalid args", K(ret), K(buf), K(len), K(pos));
+  } else if (OB_FAIL(serialization::decode(buf, len, pos, version))) {
+    LOG_WARN("failed to deserialize start transfer in mds ctx's version", K(ret), K(len), K(pos));
+  } else if (FALSE_IT(version_ = static_cast<ObStartTransferInMdsCtxVersion::VERSION>(version))) {
+  } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V1 == version_) {
+    pos = saved_pos;
+    if (OB_FAIL(MdsCtx::deserialize(buf, len, pos))) {
+      LOG_WARN("failed to deserialize mds ctx", K(ret), K(len), K(pos));
+    }
+  } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V2 == version_
+      || ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V3 == version_) {
+    if (OB_FAIL(serialization::decode_i32(buf, len, pos, &length))) {
+      LOG_WARN("failed to deserialize start transfer in mds ctx's length", K(ret), K(len), K(pos));
+    } else if (OB_UNLIKELY(length > len - saved_pos)) {
+      ret = OB_ERR_UNEXPECTED;
+      LOG_WARN("buffer's length is not enough", K(ret), K(length), K(len - pos));
+    } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V3 == version_
+        && OB_FAIL(ls_id_.deserialize(buf, len, pos))) {
+      LOG_WARN("fail to deserialize ls id", K(ret), K(len), K(pos));
+    } else if (OB_FAIL(MdsCtx::deserialize(buf, len, pos))) {
+      LOG_WARN("failed to deserialize mds ctx", K(ret), K(len), K(pos));
+    } else if (OB_UNLIKELY(length != pos - saved_pos)) {
+      ret = OB_ERR_UNEXPECTED;
+      LOG_WARN("start transfer in ctx length doesn't match standard length", K(ret), K(saved_pos), K(pos), K(length), K(len));
+    }
+  } else {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("invalid version", K(ret), K_(version));
+  }
+  return ret;
+}
+
+int64_t ObStartTransferInMdsCtx::get_serialize_size(void) const
+{
+  int64_t size = 0;
+  const int32_t placeholder_length = 0;
+  if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V1 == version_) {
+    size += MdsCtx::get_serialize_size();
+  } else if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V2 == version_
+      || ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V3 == version_) {
+    const int64_t version = static_cast<int64_t>(version_);
+    size += serialization::encoded_length(version);
+    size += serialization::encoded_length_i32(placeholder_length);
+    if (ObStartTransferInMdsCtxVersion::START_TRANSFER_IN_MDS_CTX_VERSION_V3 == version_) {
+      size += ls_id_.get_serialize_size();
+    }
+
+    size += MdsCtx::get_serialize_size();
+  }
+  return size;
+}
+
+}
+}
+}

src/storage/multi_data_source/ob_start_transfer_in_mds_ctx.h

@@ -0,0 +1,71 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#ifndef SHARE_STORAGE_MULTI_DATA_SOURCE_OB_START_TRANSFER_IN_MDS_CTX_H
+#define SHARE_STORAGE_MULTI_DATA_SOURCE_OB_START_TRANSFER_IN_MDS_CTX_H
+
+#include "mds_ctx.h"
+#include "lib/container/ob_array.h"
+#include "lib/container/ob_array_serialization.h"
+#include "share/ob_ls_id.h"
+#include "storage/multi_data_source/runtime_utility/mds_tenant_service.h"
+
+namespace oceanbase
+{
+namespace storage
+{
+namespace mds
+{
+
+class MdsTableHandle;
+
+struct ObStartTransferInMdsCtxVersion
+{
+  enum VERSION {
+    START_TRANSFER_IN_MDS_CTX_VERSION_V1 = 1,
+    START_TRANSFER_IN_MDS_CTX_VERSION_V2 = 2,
+    START_TRANSFER_IN_MDS_CTX_VERSION_V3 = 3,
+    MAX
+  };
+  static const VERSION CURRENT_CTX_VERSION = START_TRANSFER_IN_MDS_CTX_VERSION_V3;
+  static bool is_valid(const ObStartTransferInMdsCtxVersion::VERSION &version) {
+    return version >= START_TRANSFER_IN_MDS_CTX_VERSION_V1
+        && version < MAX;
+  }
+};
+
+class ObStartTransferInMdsCtx : public MdsCtx
+{
+public:
+  ObStartTransferInMdsCtx();
+  explicit ObStartTransferInMdsCtx(const MdsWriter &writer);
+  virtual ~ObStartTransferInMdsCtx();
+public:
+  virtual void on_prepare(const share::SCN &prepare_version) override;
+  virtual void on_abort(const share::SCN &abort_scn) override;
+
+  virtual int serialize(char *buf, const int64_t len, int64_t &pos) const override;
+  virtual int deserialize(const char *buf, const int64_t len, int64_t &pos) override;
+  virtual int64_t get_serialize_size(void) const override;
+public:
+  void set_ls_id(const share::ObLSID &ls_id) { ls_id_ = ls_id; }
+private:
+  ObStartTransferInMdsCtxVersion::VERSION version_;
+  share::ObLSID ls_id_;
+  DISALLOW_COPY_AND_ASSIGN(ObStartTransferInMdsCtx);
+};
+
+} //mds
+} //storage
+} //oceanbase
+
+#endif //SHARE_STORAGE_MULTI_DATA_SOURCE_OB_TRANSFER_IN_MDS_CTX_H

src/storage/multi_data_source/ob_tablet_create_mds_ctx.cpp

@@ -0,0 +1,143 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#include "storage/multi_data_source/ob_tablet_create_mds_ctx.h"
+#include "lib/utility/serialization.h"
+#include "storage/ls/ob_ls_get_mod.h"
+#include "storage/tx_storage/ob_empty_shell_task.h"
+#include "storage/tx_storage/ob_ls_service.h"
+#include "storage/tx_storage/ob_ls_handle.h"
+
+#define USING_LOG_PREFIX MDS
+
+namespace oceanbase
+{
+namespace storage
+{
+namespace mds
+{
+ObTabletCreateMdsCtx::ObTabletCreateMdsCtx()
+  : MdsCtx(),
+    magic_(MAGIC),
+    version_(VERSION),
+    ls_id_()
+{
+}
+
+ObTabletCreateMdsCtx::ObTabletCreateMdsCtx(const MdsWriter &writer)
+  : MdsCtx(writer),
+    magic_(MAGIC),
+    version_(VERSION),
+    ls_id_()
+{
+}
+
+void ObTabletCreateMdsCtx::on_abort(const share::SCN &abort_scn)
+{
+  mds::MdsCtx::on_abort(abort_scn);
+
+  // TODO(@bowen.gbw): feature branch transfer_dml_ctrl_42x patch to master,
+  // then add more logic, currently this code is just for compat
+}
+
+int ObTabletCreateMdsCtx::serialize(char *buf, const int64_t buf_len, int64_t &pos) const
+{
+  int ret = OB_SUCCESS;
+  const int64_t serialize_size = get_serialize_size();
+  int64_t tmp_pos = pos;
+
+  if (OB_ISNULL(buf)
+      || OB_UNLIKELY(buf_len <= 0)
+      || OB_UNLIKELY(pos < 0)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("invalid args", K(ret), K(buf), K(buf_len), K(pos));
+  } else if (OB_UNLIKELY(buf_len - pos < serialize_size)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("buffer len is not enough to serialize", K(ret), K(buf_len), K(pos), K(serialize_size));
+  } else if (VERSION == version_) {
+    if (OB_FAIL(MdsCtx::serialize(buf, buf_len, tmp_pos))) {
+      LOG_WARN("failed to serialize mds ctx", K(ret), K(buf_len), K(tmp_pos));
+    } else if (OB_FAIL(serialization::encode(buf, buf_len, tmp_pos, magic_))) {
+      LOG_WARN("fail to serialize magic", K(ret), K(buf_len), K(tmp_pos), K_(magic));
+    } else if (OB_FAIL(serialization::encode(buf, buf_len, tmp_pos, version_))) {
+      LOG_WARN("fail to serialize version", K(ret), K(buf_len), K(tmp_pos), K_(version));
+    } else if (OB_FAIL(serialization::encode_i64(buf, buf_len, tmp_pos, serialize_size))) {
+      LOG_WARN("fail to serialize length", K(ret), K(buf_len), K(tmp_pos), K(serialize_size));
+    } else if (OB_FAIL(ls_id_.serialize(buf, buf_len, tmp_pos))) {
+      LOG_WARN("fail to serialize ls id", K(ret), K(buf_len), K(tmp_pos), K_(ls_id));
+    } else {
+      pos = tmp_pos;
+    }
+  } else {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("unexpected version", K(ret), K_(version));
+  }
+
+  return ret;
+}
+
+int ObTabletCreateMdsCtx::deserialize(const char *buf, const int64_t buf_len, int64_t &pos)
+{
+  int ret = OB_SUCCESS;
+  int64_t tmp_pos = pos;
+  int32_t magic = -1;
+  int32_t version = -1;
+  int64_t serialize_size = 0;
+
+  if (OB_ISNULL(buf)
+      || OB_UNLIKELY(buf_len <= 0)
+      || OB_UNLIKELY(pos < 0)) {
+    ret = OB_INVALID_ARGUMENT;
+    LOG_WARN("invalid args", K(ret), K(buf), K(buf_len), K(pos));
+  } else if (OB_FAIL(MdsCtx::deserialize(buf, buf_len, tmp_pos))) {
+    LOG_WARN("fail to deserialize mds ctx", K(ret), K(buf_len), K(tmp_pos));
+  } else if (OB_FAIL(serialization::decode(buf, buf_len, tmp_pos, magic))) {
+    LOG_WARN("failed to deserialize magic", K(ret), K(buf_len), K(tmp_pos));
+  } else if (OB_UNLIKELY(magic != MAGIC)) {
+    FLOG_INFO("magic does not match, maybe this is old version data", K(ret), K(magic), LITERAL_K(MAGIC));
+    version_ = VERSION;
+    ls_id_ = ObLSID::INVALID_LS_ID;
+    pos = tmp_pos;
+  } else if (OB_FAIL(serialization::decode(buf, buf_len, tmp_pos, version))) {
+    LOG_WARN("failed to deserialize version", K(ret), K(buf_len), K(tmp_pos));
+  } else if (OB_UNLIKELY(VERSION != version)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("version does not match", K(ret), K(version));
+  } else if (OB_FAIL(serialization::decode_i64(buf, buf_len, tmp_pos, &serialize_size))) {
+    LOG_WARN("failed to deserialize serialize size", K(ret), K(buf_len), K(tmp_pos));
+  } else if (tmp_pos - pos < serialize_size && OB_FAIL(ls_id_.deserialize(buf, buf_len, tmp_pos))) {
+    LOG_WARN("failed to deserialize ls id", K(ret), K(buf_len), K(tmp_pos));
+  } else if (OB_UNLIKELY(tmp_pos - pos != serialize_size)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("deserialize length does not match", K(ret), K(buf_len), K(pos), K(tmp_pos), K(serialize_size));
+  } else {
+    version_ = version;
+    pos = tmp_pos;
+  }
+
+  return ret;
+}
+
+int64_t ObTabletCreateMdsCtx::get_serialize_size() const
+{
+  int64_t size = 0;
+  int64_t serialize_size = 0; // dummy
+  size += MdsCtx::get_serialize_size();
+  size += serialization::encoded_length(magic_);
+  size += serialization::encoded_length(version_);
+  size += serialization::encoded_length_i64(serialize_size);
+  size += ls_id_.get_serialize_size();
+  return size;
+}
+} // namespace mds
+} // namespace storage
+} // namespace oceanbase

src/storage/multi_data_source/ob_tablet_create_mds_ctx.h

@@ -0,0 +1,55 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#ifndef OCEANBASE_STORAGE_OB_CREATE_TABLET_MDS_CTX
+#define OCEANBASE_STORAGE_OB_CREATE_TABLET_MDS_CTX
+
+#include "storage/multi_data_source/mds_ctx.h"
+#include "share/ob_ls_id.h"
+
+namespace oceanbase
+{
+namespace storage
+{
+namespace mds
+{
+class ObTabletCreateMdsCtx : public MdsCtx
+{
+public:
+  ObTabletCreateMdsCtx();
+  explicit ObTabletCreateMdsCtx(const MdsWriter &writer);
+  virtual ~ObTabletCreateMdsCtx() = default;
+public:
+  virtual void on_abort(const share::SCN &abort_scn) override;
+  virtual int serialize(char *buf, const int64_t buf_len, int64_t &pos) const override;
+  virtual int deserialize(const char *buf, const int64_t buf_len, int64_t &pos) override;
+  virtual int64_t get_serialize_size() const override;
+public:
+  void set_ls_id(const share::ObLSID &ls_id);
+private:
+  static constexpr int32_t MAGIC = 0xdead;
+  static constexpr int32_t VERSION = 1;
+
+  const int32_t magic_;
+  int32_t version_;
+  share::ObLSID ls_id_;
+};
+
+inline void ObTabletCreateMdsCtx::set_ls_id(const share::ObLSID &ls_id)
+{
+  ls_id_ = ls_id;
+}
+} // namespace mds
+} // namespace storage
+} // namespace oceanbase
+
+#endif // OCEANBASE_STORAGE_OB_CREATE_TABLET_MDS_CTX