What factors should be taken into consideration when setting a value for background-validation-millis parameter in JBoss EAP 5.x/6.x

Environment

• Red Hat JBoss Enterprise Application Platform (EAP)
  • 5.x
  • 6.x

Issue

• What is the default value for <background-validation-millis> parameter in the data source configuration settings?
• What factors should be taken into consideration when setting a value for <background-validation-millis> parameter?

Resolution

The default value for <background-validation-millis> parameter is 0 milliseconds[¹]. This also implies background validation is disabled. This value should not be the same as your <idle-timeout-minutes> value. Please also refer to this document [²] for more information.

The main consideration when setting <background-validation-millis> is that the lower the value the more often the pool will be validated which will take up more database resources. Also the lower the value the sooner invalid connections will be evicted from the pool. On one hand too low of an value (meaning validation is occurring too often) can stress the connection pool resources. On the other hand, if the value is set too high (meaning validation is not occurring frequently enough) then the dead connections will go undetected for longer periods. Therefore it is a balancing act to determine the correct value for a particular system.

If the minimal performance hit is not a concern then using <validate-on-match> is a safer approach than <background-validation-millis>. These articles [³] and [⁴] elaborate on this topic.

References:

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