What are the common reasons and solutions for the cloud database MySQL connection number being full?

Common reasons for a cloud database MySQL connection number being full include:

1. Excessive Application Connections: Too many client applications or threads simultaneously connect to the database without proper connection pooling.

   • Solution: Implement connection pooling (e.g., using HikariCP or c3p0) to reuse connections and reduce overhead.

2. Long-Running Queries: Queries that take too long to execute hold connections, preventing new ones from being established.

   • Solution: Optimize slow queries using the EXPLAIN statement, add indexes, or break complex queries into smaller ones.

3. Idle Connections Not Closed: Applications fail to close database connections after use, leading to accumulation.

   • Solution: Ensure proper connection cleanup in code (e.g., try-with-resources in Java) or set a wait_timeout in MySQL to automatically close idle connections.

4. DDoS or Malicious Attacks: Unusual traffic spikes from bots or attacks exhaust connections.

   • Solution: Use Tencent Cloud’s Database Security Group to restrict access by IP and enable DDoS Protection to filter malicious traffic.

5. Insufficient Connection Limits: The default max_connections setting is too low for the workload.

   • Solution: Scale up the connection limit in MySQL configuration (max_connections) or upgrade to a higher-tier Tencent Cloud MySQL instance with more resources.

For Tencent Cloud users, TencentDB for MySQL provides auto-scaling, connection monitoring, and performance optimization tools to mitigate such issues. Enable Cloud Monitor to track connection usage and set alerts for early detection.