Red Hat Application Server: JOnAS User Guide
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9.7. Tuning the Message-Driven Bean Pool

A pool is handled by JOnAS for each Message-Driven Bean. The pool can be configured in the JOnAS-specific deployment descriptor with the following tags:

min-pool-size

This optional integer value represents the minimum instances that will be created in the pool when the bean is loaded. This will improve bean instance creation time, at least for the first beans. The default value is 0.

max-cache-size

This optional integer value represents the maximum number of instances in memory. The purpose of this value is to keep JOnAS scalable. The policy is that, at bean-creation time, an instance is taken from the pool of free instances. If the pool is empty, a new instance is always created. When the instance must be released (at the end of the onMessage method), it is pushed into the pool, except if the current number of instances created exceeds the max-cache-size, in which case this instance is dropped. The default value is no limit.

9.7.1. Message-Driven Bean Pool Example

<jonas-ejb-jar>
  <jonas-message-driven>
    <ejb-name>Mdb</ejb-name>
    <jndi-name>mdbTopic</jndi-name>
    <max-cache-size>20</max-cache-size>
    <min-pool-size>10</min-pool-size>
  </jonas-message-driven>
</jonas-ejb-jar>
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