Master MySQL Clone Plugin: Installation, Usage, and Optimization

Overview

The Clone Plugin, introduced in MySQL 8.0.17, enables a built‑in, single‑command method to clone a MySQL instance for adding nodes to Group Replication or ordinary master‑slave topologies.

Installation

Two installation methods are supported:

Add plugin-load-add=mysql_clone.so to the [mysqld] section of my.cnf and restart the server.

Load the plugin at runtime: INSTALL PLUGIN clone SONAME 'mysql_clone.so'; Verify with SHOW PLUGINS;; the plugin should appear with ACTIVE status.

Local Clone

Clones data from the current instance to a directory on the same host.

Create a clone user with the required privilege:

CREATE USER 'clone_user'@'%' IDENTIFIED BY 'clone_pass';
GRANT BACKUP_ADMIN ON *.* TO 'clone_user'@'%';

Prepare an empty, writable directory (absolute path). Example:

mkdir -p /data/backup
chown -R mysql.mysql /data/backup

Execute the clone command: CLONE LOCAL DATA DIRECTORY='/data/backup/3307'; Start a new instance that points to the cloned directory:

mysqld --no-defaults --datadir=/data/backup/3307 --user=mysql --port=3307 &

Directory requirements: absolute path, must exist, writable by MySQL, and the final sub‑directory (e.g., 3307) must not already exist.

Remote Clone

Clones data from a donor instance to a recipient over the network.

On the donor, create a clone user and load the plugin:

CREATE USER 'donor_user'@'%' IDENTIFIED BY 'donor_pass';
GRANT BACKUP_ADMIN ON *.* TO 'donor_user'@'%';
INSTALL PLUGIN clone SONAME 'mysql_clone.so';

On the recipient, create a clone user with CLONE_ADMIN (includes BACKUP_ADMIN and SHUTDOWN) and load the plugin:

CREATE USER 'recipient_user'@'%' IDENTIFIED BY 'recipient_pass';
GRANT CLONE_ADMIN ON *.* TO 'recipient_user'@'%';
INSTALL PLUGIN clone SONAME 'mysql_clone.so';

Set the donor whitelist on the recipient (requires SYSTEM_VARIABLES_ADMIN):

SET GLOBAL clone_valid_donor_list='192.168.244.10:3306';

Run the remote clone command:

CLONE INSTANCE FROM 'donor_user'@'192.168.244.10':3306 IDENTIFIED BY 'donor_pass' [DATA DIRECTORY='clone_dir'];

The remote clone performs the following steps on both donor and recipient:

Acquire a backup lock (DDL is blocked unless clone_block_ddl is OFF).

Drop user tablespaces (system files are renamed with a .#clone suffix).

Copy data files from the donor.

Restart the recipient, replacing original system files with the .#clone versions.

Monitoring Clone Progress

Two performance_schema tables provide insight:

clone_status – a single‑row table showing overall state, timestamps, source/destination, error codes, and GTID/binlog positions.

clone_progress – one row per stage (DROP DATA, FILE COPY, PAGE COPY, REDO COPY, FILE SYNC, RESTART, RECOVERY) with columns such as STAGE, STATE, BEGIN_TIME, END_TIME, THREADS, ESTIMATE, DATA, NETWORK, DATA_SPEED, NETWORK_SPEED.

Building a Replica from Cloned Data

Two replication setups are covered:

GTID‑based replication – enable automatic positioning:

CHANGE MASTER TO MASTER_HOST='master_host', MASTER_PORT=3306, MASTER_AUTO_POSITION=1;
START SLAVE;

Position‑based replication – retrieve BINLOG_FILE and BINLOG_POSITION from clone_status and use them:

CHANGE MASTER TO MASTER_HOST='master_host', MASTER_PORT=3306,
MASTER_LOG_FILE='mysql-bin.000004', MASTER_LOG_POS=139952824;
START SLAVE;

When using the Clone Plugin, GTID variables ( GTID_PURGED, GTID_EXECUTED) are already correct, so no manual SET GLOBAL GTID_PURGED is required.

Implementation Details

The clone operation consists of five internal phases:

INIT – create a clone object.

FILE COPY – copy InnoDB data files while recording the start LSN and enabling page tracking.

PAGE COPY – copy only the pages that changed after the start LSN, sorted to reduce random I/O; redo archiving is started.

REDO COPY – copy redo logs generated between the start and end LSNs.

DONE – call snapshot_end() to destroy the clone object.

Requirements and Limitations

DDL is blocked on the donor during cloning (except MySQL 8.0.27+ where donor DDL no longer blocks).

Configuration parameters, binary logs, and non‑InnoDB tables are not copied.

Only InnoDB table data is cloned; other storage engines copy only the schema.

Donor and recipient must run the same MySQL version, OS, architecture, character set, and innodb_page_size.

Recipient needs sufficient disk space and must be managed by mysqld_safe or systemd for automatic restart.

Only one clone operation can run on a given instance at a time.

Donor port must be a classic MySQL port (X Protocol ports are not supported).

Clone Plugin vs. Percona XtraBackup

Both perform FILE COPY and REDO COPY; Clone adds a PAGE COPY stage, resulting in faster recovery.

XtraBackup lacks redo archiving, risking loss of redo logs generated during copy.

When using GTID, Clone does not require a manual SET GLOBAL GTID_PURGED step.

Configuration Parameters

clone_autotune_concurrency – ON/OFF automatic thread‑count tuning (default ON; max threads controlled by clone_max_concurrency).

clone_block_ddl – whether to acquire a backup lock on the donor (blocks DDL, default OFF, introduced in 8.0.27).

clone_delay_after_data_drop – wait time after dropping user tablespaces before copying data (default 0 s, introduced in 8.0.29).

clone_buffer_size – size of the local clone buffer (default 4 MiB).

clone_ddl_timeout – max wait time for a backup lock before the clone aborts (default 300 s).

clone_donor_timeout_after_network_failure – wait time after a network error before aborting (default 5 min, configurable from 8.0.24).

clone_enable_compression – enable compression for remote data transfer (default OFF).

clone_max_data_bandwidth – max data copy rate in MiB/s (0 = unlimited).

clone_max_network_bandwidth – max network transfer rate in MiB/s (0 = unlimited).

clone_valid_donor_list – comma‑separated whitelist of donor hosts.

clone_ssl_ca / clone_ssl_cert / clone_ssl_key – SSL configuration for secure remote cloning.

References

InnoDB: Clone local replica – https://dev.mysql.com/worklog/task/?id=9209

InnoDB: Clone remote replica – https://dev.mysql.com/worklog/task/?id=9210

InnoDB: Clone replication coordinates – https://dev.mysql.com/worklog/task/?id=9211

InnoDB: Clone remote provisioning – https://dev.mysql.com/worklog/task/?id=11636

MySQL/InnoDB data clone plugin analysis (Chinese) – https://zhuanlan.zhihu.com/p/79328512