Qinglin Zhang, Database Kernel Engineer at Tencent, introduces CynosDB, Tencent's self-developed database for the cloud. CynosDB is based on MariaDB Server, but separates computing and storage. Zhang goes on to provide a detailed explanation of the architecture with a focus on how Tencent implemented the computing and storage layers, and created Tencent’s MariaDB-based “Aurora”.

1. Qinglin Zhang
TXSQL Team @ Tencent
CynosDB @ Tencent Cloud
guyue.zql@gmail.com

2. Preview
Tencent
Tencent Cloud
TXSQL
CDB

3. Agenda
• Why CynosDB ?
• Architecture
• TXStore for CynosDB
• TXSQL for CynosDB
• Future of CynosDB

4. Why CynosDB？

5. User Challenges:
✓ Scalability: fast scale up/down, fast scalable read
✓ Cost: pay on-demand
✓ Replication: binlog, DDL/big transaction
✓ BufferPool: read & write cache, the disadvantage of flushing
Traditional MySQL Challenges:

6. The Architecture of CynosDB

7. ✓ Separate storage from MySQL
✓ Log is database, write once
Architecture
slave
TXSQL
master
TXSQL
slave
TXSQL
…CELL CELL CELLCELL
TXStore
MDS
redo

8. TXStore for CynosDB

9. TXStore core for CynosDB
✓ Replication protocol
✓ Computational storage
✓ Multi version page

10. MySQL Master
SQL Layer
Engine Layer
①send log record
LogPool
RingQueue
MemTable
InnoDB Page
③ack
②Replicate log record
Primary Storage Node
Replica Storage Node
Replica Storage Node
④push to memtable
⑤Apply logs to InnoDB Page
sync
async
TXStore core details
Disk
②flush to disk

11. TXStore performance for CynosDB
✓ SPDK（user space api）
✓ RDMA
✓ Reconstruct redo log
✓ …
✓ Jemalloc integrated

12. TXSQL for CynosDB

13. The Brief of TXSQL
✓ Tencent MySQL(Compatible with Oracle MySQL5.5/5.6/5.7)
✓ Support Tencent Cloud (TencentDB for CDB)
✓ The Component of TXSQL
TXSQL for MySQL TXSQL for NewCDB TXSQL for RocksDB
TXSQL CynosDB TXRocks TXTools
Backup/Recovery/Checksum

14. TXSQL core for CynosDB
✓ Crash Recovery
✓ Remote Storage based on TXStore
✓ System tables converted to Innodb
✓ Redo log Replication
✓ Redo for bulk load create index
✓ Parallel redo log copy optimization
✓ MVCC

15. Parallel redo log copy optimization
mtr_commitTrx_1
Trx_2
Trx_m
mtr_commit
Reduce log_sys->mutex occupancy time to improve perforemance
mtr_commit
mutex_enter calc lsn mutex_exit copy redo log
mutex_enter calc lsn mutex_exit copy redo log
mutex_enter calc lsn mutex_exit copy redo log

16. Parallel redo log replication
mtr_commit
mtr_commit
……
mtr_commit
log_sys->write_buf
log_write_thread
redo_log_receiver_thread redo_log_coor_thread
redo_log_worker_thread
redo_log_worker_thread
redo_log_worker_thread

17. TXSQL performance for CynosDB
✓ Redo Log optimization for flush
✓ Asyc Thread Pool Commit
✓ Trx sys optimization
✓ …
✓ Jemalloc integrated
✓ Async DDL Replication

18. Async Thread Pool Commit
listener thread (pollfd)
... wroker threadwroker thread
high_prio_queue queue
handle_event
get_event
handle_event
get_event
clientclient …… client
thread_group_oversubscribe
log_write_up_to log_write_up_to
✓ Sync wait converted to async
✓ Enlarge high-priority-queue
✓ Thread pool & one-thread-per-connection

19. Async DDL Replication
Async DDL Support in CynosDB
Frm files stored in Innodb
Multi page version from TXStore
Synchronized by redo log

20. master slave
read old Table
begin
end
DDL start
DDL end
read new Table
table was locked
Asynchronous DDL
cost most time of DDL,replica can read
cost little time of DDL,master can't read

21. TXSQL feature for CynosDB
✓ Aggregate pushdown to InnoDB
✓ Enterprise Encryption
✓ INVISIBLE INDEX
✓ Instant DDL Operation
✓ Asynchronous DROP TABLE
✓ …

22. Instant DDL Operation
✓ Add column at designed order
✓ Change column order
✓ Change default value

23. Future of CynosDB
✓ CDBTune（Intelligent tuning）
✓ Multi Master
✓ …
✓ PITR