Error
Error Code:
3085
MySQL Error 3085: Slave SQL Thread Running
Description
This error indicates that you are attempting a MySQL replication operation that requires the slave SQL thread to be stopped. It occurs when a command, such as altering replication settings or resetting a slave, is issued while the SQL thread is actively processing replication events.
Error Message
This operation cannot be performed with a running slave sql thread; run STOP SLAVE SQL_THREAD FOR CHANNEL '%s' first.
Known Causes
3 known causesIncompatible Replication Operation
Certain MySQL replication commands, like `CHANGE MASTER TO` or `RESET SLAVE`, require the SQL thread to be inactive to prevent data inconsistencies.
Prerequisite Step Overlooked
The necessary step of stopping the slave SQL thread was not performed before attempting the desired replication command.
Automated Script Logic
An automated script or application attempted a replication operation without first verifying or stopping the slave SQL thread status.
Solutions
3 solutions available1. Gracefully Stop and Restart the Slave SQL Thread easy
The recommended approach is to stop the SQL thread, perform the operation, and then restart it.
1
Connect to your MySQL replica server using a client (e.g., mysql client).
2
Execute the command to stop the SQL thread. Replace '%s' with the actual channel name if you are using named replication channels. If not, you can omit it.
STOP SLAVE SQL_THREAD FOR CHANNEL 'your_channel_name';
-- or if no named channel is used:
STOP SLAVE SQL_THREAD;3
Perform the operation that was blocked by the running SQL thread. This could be altering a table, dropping a table, etc.
4
Once the operation is complete, restart the SQL thread.
START SLAVE SQL_THREAD FOR CHANNEL 'your_channel_name';
-- or if no named channel is used:
START SLAVE SQL_THREAD;5
Verify the replication status to ensure it's running correctly.
SHOW SLAVE STATUS FOR CHANNEL 'your_channel_name'\G
-- or if no named channel is used:
SHOW SLAVE STATUS\G2. Check Replication Status and Identify the Blocking Operation medium
Understand why the SQL thread is running and if it's stuck on a specific transaction.
1
Connect to your MySQL replica server.
2
Check the slave status to see if the SQL thread is indeed running and if there are any errors or delays.
SHOW SLAVE STATUS FOR CHANNEL 'your_channel_name'\G
-- or if no named channel is used:
SHOW SLAVE STATUS\G3
Pay close attention to `Seconds_Behind_Master` and any error messages. If `Seconds_Behind_Master` is high or there are errors, the SQL thread might be stuck on a specific transaction.
4
If you suspect a specific transaction is causing the issue, you might need to investigate logs on the source server or use replication debugging tools.
5
Once the blocking operation is identified and resolved (potentially on the source server), you can then proceed with stopping and restarting the SQL thread as in Solution 1.
3. Temporarily Halt Replication Entirely (Use with Caution) medium
Stop both I/O and SQL threads to perform maintenance, but be aware of potential data drift.
1
Connect to your MySQL replica server.
2
Stop both the I/O and SQL threads. This will halt all replication activity.
STOP SLAVE FOR CHANNEL 'your_channel_name';
-- or if no named channel is used:
STOP SLAVE;3
Perform your maintenance operation that requires replication to be stopped.
4
After the operation, carefully restart the replication threads.
START SLAVE FOR CHANNEL 'your_channel_name';
-- or if no named channel is used:
START SLAVE;5
Monitor `SHOW SLAVE STATUS` closely to ensure replication catches up and remains in sync.
SHOW SLAVE STATUS FOR CHANNEL 'your_channel_name'\G
-- or if no named channel is used:
SHOW SLAVE STATUS\G