Error
Error Code:
1755
MariaDB Error 1755: Parallel Replication Event Group Blocked
Description
MariaDB Error 1755 indicates that the replica's multi-threaded replication (MTS) mechanism cannot execute a specific group of events in parallel mode. This occurs when an event within the group is identified as unsafe for concurrent application, forcing the replica to either serialize its execution or halt due to an unresolvable conflict preventing parallel processing.
Error Message
Cannot execute the current event group in the parallel mode. Encountered event %s, relay-log name %s, position %s which prevents execution of this event group in parallel mode. Reason: %s.
Known Causes
4 known causesDDL Statements in Event Group
The event group contains Data Definition Language (DDL) statements (e.g., ALTER TABLE, CREATE INDEX), which are inherently difficult or unsafe to parallelize and often require serialization to maintain data consistency.
Non-Transactional Table Updates
Updates or modifications to tables using non-transactional storage engines like MyISAM can prevent parallel execution, as their operations lack the atomicity and isolation required for safe concurrent application.
Events Affecting Global Server State
The event group includes operations that affect global server state or configuration (e.g., FLUSH commands, operations on system tables), which MariaDB deems unsafe for parallel processing.
Complex Event Group Dependencies
The MariaDB replication logic has detected complex dependencies or potential conflicts between events within the current group, making it impossible or unsafe to execute them in parallel.
Solutions
Coming SoonDetailed step-by-step solutions for this error are being prepared. In the meantime, try these general troubleshooting tips:
General Troubleshooting Tips
- Check the error message carefully for specific details
- Review recent changes that might have caused the error
- Search for the exact error code in the official documentation
- Check log files for additional context
- Try restarting the application or service