Lesson Learned #509: KeepAliveTime parameter in HikariCP

Using network tracing, I observed that once a connection is established, the operating system sends TCP keepalives to keep it alive. This indicates how often the connection is checked to see if it remains active in the HikariCP connection pool.

In this situation, my first idea for idle connections in the HikariCP pool was to configure the KeepAliveTime parameter. HikariCP sends a simple query (e.g. SELECT 1) to idle connections that have been inactive for longer than the value of this parameter. This will maintain the connection and prevent unexpected disconnection by external systems.

You can view the results in the following network traces and SQL Profiler:

Network settings related to firewalls have policies that close idle connections after a certain period of time. In this way, if a connection is closed and no keepalivetime is set, HikariCP will only detect the closure when the connection is requested from the pool.

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