Reasonably set the maximum number of connections, control waiting and timeout mechanisms, maintain healthy connections, and optimize management under the database and tables. The configuration of MySQL connection pool is crucial under high concurrency. The maximum number of connections should be slightly lower than the database upper limit and combined with monitoring adjustments. ConnectionTimeout and SQL execution timeout mechanisms need to be set to prevent thread accumulation; connection detection and idle recycling mechanisms are enabled to ensure connection effectiveness; in scenarios such as read and write separation or database separation and table separation, each data source should independently configure connection pools and adjust the size according to traffic allocation to improve overall performance and stability.

In high concurrency environments, the rational use of MySQL connection pool is crucial to system performance. If the connection pool is not configured properly, the database can easily become a bottleneck, slow response or even crash. This article focuses on several practical connection pooling strategies to help you sustain greater concurrency pressure.

Set the maximum number of connections reasonably

The maximum number of connections in the connection pool is not the larger the better, nor is it the smaller the easier it is to save trouble. This value depends on the carrying capacity of your database server and the actual application requirements.

• If you are using a cloud database (such as AWS RDS or Alibaba Cloud MySQL), there is usually a maximum number of connections, and an error will be reported if it exceeds it.
• If the application level is set too high, it may get stuck before the database is reached; if it is too low, the request queue will be severely affected, which will affect the user experience.

Suggested practices:

• Monitor the current active connections and load status of the database
• Set the upper limit of the connection pool slightly lower than the maximum number of connections allowed by the database (for example, reserve 10% for other services)
• Using efficient connection pooling components like HikariCP and Druid, they are more stable in controlling connections

Control connection waiting time and timeout mechanism

The connection pool resources are limited. When the concurrent request exceeds the pool capacity, subsequent requests will enter a waiting state. Without a reasonable waiting and timeout mechanism, threads will accumulate and eventually drag down the entire service.

FAQ:

• The timeout time to get the connection is not set, causing the request to "stagnate"
• After obtaining the connection, the SQL timeout is not released, occupying resources

Recommended configuration:

• Set connectionTimeout , such as 500ms, to avoid infinite waiting
• Sets the statement timeout or transaction timeout executed by SQL
• There must be appropriate downgrade logic after a timeout, such as returning a prompt or recording a log

Keep healthy connections with idle recycling mechanisms using connection testing

The connections in the connection pool may fail due to network fluctuations, database restarts, etc. If these connections are not cleaned up in time, an error will occur during subsequent use, affecting the business.

How to deal with it?

• Turn on connection validity detection (such as validationQuery or connectionTestQuery )
• Set idle connection recycling time (idleTimeout) to avoid long-term idle and waste resources
• Keepalive regularly

Different connection pool implementations are slightly different, but the core ideas are consistent. For example, HikariCP recommends using isReadOnly or isValid() methods for quick detection instead of executing SQL every time.

Connection pool management under library and table separation or read and write separation

If you have done reading and writing separation or library separation, each data source needs to be configured independently, otherwise it is easy to have resource scrambles or configuration confusion.

Typical practices:

• Different data sources use different connection pool instances
• Adjust the size of each pool according to the traffic allocation ratio
• Relax the upper limit of the connection pool for read-only nodes as queries generally release connections faster

For example, in an e-commerce system, the main library is responsible for writing and the two slave libraries are responsible for reading. Then you can set up a smaller connection pool for the main library and set up a slightly larger pool for each slave library to balance the load.

Basically these key points. The connection pool looks simple, but if it really needs to be configured well, it still needs to be continuously tuned in combination with monitoring data.

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