Oracle connection pooling takes a lot of time for first call - spring

Question

In spring I have a datasource defined in this way:
<bean id="dataSource" class="oracle.jdbc.pool.OracleDataSource" destroy-method="close">
<property name="URL" value="${jdbc.url}" />
<property name="user" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
<property name="connectionCachingEnabled" value="true"/>
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource" />
</bean>
This datasource is used by my REST service and everything works fine...anyway first REST call is very slow (about ~5 secs), after that EVERY other call is fast.
I think this is an initialization related problem, in the sense that initialization is made when first DB call is received.
Is there a way to tell spring to initialize this datasource on server startup?

Answer 1

I think this is an initialization related problem, in the sense that
initialization is made when first DB call is received.
With your current config I think that's what's happening.
Is there a way to tell spring to initialize this datasource on server
startup?
It's the behavior of the connection pool, not Spring. Spring is creating the bean when your app starts (you aren't using lazy-init="true" on the bean). However, the connection pool isn't creating connections to the database when Spring instantiates it. From the Oracle docs:
The initial pool size property specifies the number of available
connections that are created when the connection pool is initially
created or re-initialized. This property is typically used to reduce
the ramp-up time incurred by priming the pool to its optimal size.
A value of 0 indicates that no connections are pre-created. The
default value is 0.
Try setting a non-zero value for initialPoolSize.
Edit: Try setting ConnectionCacheProperties instead:
<property name="connectionCacheProperties">
<props merge="default">
<prop key="InitialLimit">5</prop>
</props>
</property>