terrymanu commented on issue #29734:
URL:
https://github.com/apache/shardingsphere/issues/29734#issuecomment-3471283796
### Root Cause Analysis
The deadlock in your distributed ID generator scenario appears to be
caused by:
1. **XA Transaction Lock Behavior**: XA transactions in ShardingSphere may
hold locks longer than expected, especially under high concurrency
2. **Shard-Specific Lock Ordering**: Different shards might acquire locks
in varying orders, leading to circular wait conditions
3. **Optimistic Locking Pattern**: Your retry mechanism with version
checking can exacerbate lock contention when combined with XA transactions
### Recent Relevant Fixes (2024-2025)
Our team has made several improvements that may address this issue:
- **Enhanced Deadlock Test Coverage**: Improved test reliability for
deadlock scenarios across different MySQL versions
- **XA Transaction Optimizations**: Decoupled XA handlers and improved
connection management
- **Cross-Database Compatibility**: Made deadlock detection more robust
across different database versions
### Immediate Recommendations
1. **Upgrade to Latest Version**
```xml
<!-- Try upgrading to 5.5.2 or later -->
<dependency>
<groupId>org.apache.shardingsphere</groupId>
<artifactId>shardingsphere-jdbc-core</artifactId>
<version>5.5.2</version>
</dependency>
2. Configuration Tuning
- Adjust XA transaction timeout settings
- Consider reducing retry attempts in your ID generator
- Monitor lock wait timeout values
3. Alternative Approach
Consider using database sequence or Snowflake-style ID generation if the
deadlock persists
Request for Additional Information
- Database version and configuration
- Complete ShardingSphere configuration
- Whether the issue persists after upgrading to 5.5.2
Thank you for your contribution to improving ShardingSphere!
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