Error
Error Code:
3081
MySQL Error 3081: Operation Blocked by Active Replication
Description
This error occurs when you attempt to perform an operation on a MySQL server that requires replication threads to be stopped, but they are currently active. It typically happens when managing replication channels, altering replication configuration, or executing certain DDL statements. The server prevents the operation to maintain data consistency and prevent potential conflicts.
Error Message
This operation cannot be performed with running replication threads; run STOP REPLICA FOR CHANNEL '%s' first
Known Causes
3 known causesModifying Replication Configuration
You attempted to alter replication source settings or other replication parameters while the replica threads were actively running.
Conflicting DDL Operations
An attempt was made to execute a Data Definition Language (DDL) statement that is incompatible with an actively running replication channel.
Channel Management Conflicts
This error can occur when attempting to manage (e.g., drop or recreate) a replication channel that is still actively processing events.
Solutions
3 solutions available1. Temporarily Stop Replication Threads easy
Gracefully stop replication threads to perform the operation, then restart them.
1
Identify the replication channel(s) that are active. If you are unsure, you can check `SHOW REPLICA STATUS` or `SHOW SLAVE STATUS` (for older MySQL versions). Look for `Replica_IO_Running` and `Replica_SQL_Running` (or `Slave_IO_Running` and `Slave_SQL_Running`). The channel name is usually `''` (empty string) for the default channel, or a specific name if you have configured multiple channels.
SHOW REPLICA STATUS;2
Stop the replication threads for the identified channel(s). Replace `'%s'` with the actual channel name (e.g., `''` for default, or a named channel).
STOP REPLICA FOR CHANNEL '%s';3
Perform the operation that was blocked by replication (e.g., dropping a table, altering a schema).
-- Your DDL or DML statement here
-- Example: ALTER TABLE my_table ADD COLUMN new_column INT;4
Restart the replication threads. Replace `'%s'` with the actual channel name.
START REPLICA FOR CHANNEL '%s';5
Verify that replication is running again by checking the status.
SHOW REPLICA STATUS;2. Restart MySQL Server (Use with Caution) medium
Restarting the MySQL server will stop all replication threads, allowing the operation to proceed.
1
This is a more disruptive approach and should be used when other methods are not feasible or when the server can tolerate a restart. Ensure you have a maintenance window planned.
2
Gracefully stop the MySQL server. The command may vary depending on your operating system and installation method.
# For systemd-based systems (e.g., Ubuntu 15.04+, CentOS 7+)
sudo systemctl stop mysql
# For older init.d systems (e.g., Ubuntu 14.04, CentOS 6)
sudo service mysql stop3
Perform the operation that was blocked by replication.
-- Your DDL or DML statement here4
Start the MySQL server.
# For systemd-based systems
sudo systemctl start mysql
# For older init.d systems
sudo service mysql start5
After the server starts, replication threads will automatically try to resume. You can verify their status.
SHOW REPLICA STATUS;3. Identify and Address the Replication Lag Cause advanced
Investigate why replication is running slowly and fix the underlying issue to prevent future blocks.
1
Examine `SHOW REPLICA STATUS` output for indicators of replication lag, such as a large `Seconds_Behind_Master` value, or `Replica_SQL_Running` being `No` with an error message. If `Replica_SQL_Running` is `No`, check the error details provided.
SHOW REPLICA STATUS;2
Analyze the replication error logs on the replica server for specific details about why the SQL thread is stopping or lagging.
tail -f /var/log/mysql/error.log3
Common causes include: network issues, slow disk I/O on the replica, unoptimized queries on the source, large transactions, or insufficient hardware resources on the replica. Address these issues based on your findings.
4
Once the underlying cause of replication lag or failure is resolved, you can then use `STOP REPLICA FOR CHANNEL '%s'` and `START REPLICA FOR CHANNEL '%s'` to perform your operation and resume replication.
STOP REPLICA FOR CHANNEL '%s';
-- Perform your operation
START REPLICA FOR CHANNEL '%s';