MariaDB is not doing anything, why is the CPU utilization rate reaching 50%?

MariaDB may show high CPU utilization (e.g., 50%) even when it appears idle due to several reasons. Here are common causes with examples:

1. Background Processes: MariaDB runs background tasks like purging binary logs, flushing buffers, or InnoDB checkpointing. These tasks consume CPU even if no active queries are executed.
   Example: If innodb_flush_log_at_trx_commit=1 (default), frequent log flushing can spike CPU.

2. Query Cache or Statistics Updates: The query cache may be invalidating entries, or the optimizer is updating statistics.
   Example: Frequent ANALYZE TABLE operations or a large query cache with many invalidations.

3. Connection Overhead: Idle connections still consume resources if connection pooling is misconfigured.
   Example: A connection pool with too many idle connections (e.g., 100+ connections with no active queries).

4. System-Level Tasks: The OS or other processes (e.g., mysqld_safe) may temporarily spike CPU, affecting MariaDB’s metrics.

5. Resource-Intensive Configurations: Settings like sync_binlog=1 or high innodb_io_capacity can cause frequent disk I/O, leading to CPU wait states.

Mitigation:

• Use SHOW PROCESSLIST to check for hidden queries.
• Monitor slow logs (slow_query_log=ON) to identify inefficient queries.
• Adjust configurations (e.g., reduce query_cache_size if unused).
• Use Tencent Cloud Database MariaDB for auto-tuning, performance monitoring, and scalability. Its Cloud Monitor service helps pinpoint CPU spikes and optimize resources.