您如何配置无状态EJB（JBOSS）的最小实例？

Question

I have a stateless ejb that takes some time to initialize. To avoid this cost, I'd like there to always be a min number of this EJB instantiated. Is there something like minInstances that I can configure on a bean basis similar to MDB minInstances? How can I accomplish this?

Answer 1

Taking a look at the StrictMaxPool implementation used in Wildfly 10.x, there is no option to set a minimum size.

The XSD wildfly-ejb3_4_0.xsd does also not know something about a min size:

<xs:complexType name="strict-max-poolType">
    <xs:attribute name="name" type="xs:string" use="required"/>
    <xs:attribute name="max-pool-size" type="xs:positiveInteger" default="20" use="optional"/>
    <xs:attribute name="derive-size" type="xs:string" use="optional"/>
    <xs:attribute name="instance-acquisition-timeout" type="xs:positiveInteger" default="5" use="optional"/>
    <xs:attribute name="instance-acquisition-timeout-unit" type="timeout-unitType"
                  default="MINUTES" use="optional"/>
</xs:complexType>

On the other hand, the release method of the StricMaxPool does put all released beans back:

public void release(T obj) {
        if (ROOT_LOGGER.isTraceEnabled()) {
            ROOT_LOGGER.tracef("%s/%s Free instance: %s", pool.size(), maxSize, this);
        }

        pool.add(obj);

        semaphore.release();
    }

This means that once you have created max-pool-size beans, the pool won't shrink. Hence you can implement some @Startup bean that fills the pool during startup.