DBLE 3.21.10.0 Release Notes: New Features, Bug Fixes, and LTS Updates

1. DBLE Project Overview

DBLE is an enterprise‑grade open‑source distributed middleware, nicknamed “MyCat Plus”, known for its simplicity, stability, continuous maintenance, active community, and broad user base.

Official project: https://github.com/actiontech/dble

Documentation (updated): https://actiontech.github.io/dble-docs-cn

Download and release notes: https://github.com/actiontech/dble/releases

2. Main Updates in Version 3.21.10.0

This is the third release of DBLE in 2023, introducing three new/restructured features and fixing more than seven defects, with no compatibility changes.

Support for a single DBLE node to detach from or rejoin the cluster – allows temporary disconnection from the cluster center (e.g., Zookeeper) without restarting, enabling a pseudo‑cluster single‑instance mode for maintenance or upgrades.

New traffic control – adds backend read water‑level monitoring and connection‑level write‑queue length feedback to prevent memory buildup during large file loads or result‑set queries, reducing OOM risk and stabilizing memory usage.

Default sharding mode (alpha feature) – provides an out‑of‑the‑box sharding configuration.

Thanks to community contributors and users for issues, stars, and feedback.

3. Full Release Notes

Features

[#2866] Support single DBLE detach/reattach from cluster (see documentation).

[#2844] Support default sharding mode (alpha).

[#2845] New traffic control with backend read water‑level.

Major Bug Fixes

[#11] EPollArrayWrapper.epollWait could cause 100% CPU usage.

[#2896] SHOW @@dbInstance command always displayed READ_LOAD and WRITE_LOAD as 0.

[#2747] fakeMySQLVersion does not support MariaDB 10.x.

[#2750] Support add/truncate/drop partition.

[#2611] Optimized ER table issues.

[#2828] Three‑table JOIN results could be incorrect.

Occasional complex queries could cause memory leaks.

Incompatibilities with previous versions

None.

4. LTS Version Updates

Minor LTS releases fix various bugs. Notable fixes include intermittent hangs when disabling dbGroup, connection‑count leaks, MySQL instance state issues, memory leaks in complex queries, autocommit=true problems, and errors when executing SHOW @@connection.sql on management ports.

Specific LTS versions addressed:

3.20.07.7 – multiple bug fixes.

3.20.10.7 – added autocommit and SHOW @@connection.sql fixes.

3.21.02.4 – extended bug list including cluster DDL hangs.

3.21.06.2 – similar fixes and memory leak resolutions.

The release concludes with a brief note and links to recent related articles about DBLE read/write separation, Druid connection pool parameters, and DBLE query push‑down optimization.