CODEWITHSUNDEEP
javaspringjakarta-eejerseyjetty
ktm5124
ktm5124

Reputation: 12123

How will this connection pooling scenario pan out?

We have a web application that uses C3P0 to pool our connections. We inject C3P0 as a data source into JdbcTemplate. You can see how we do this here:

<bean id="dataSourceDev" class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <property name="driverClass" value="${databasedev.driver}" />
    <property name="jdbcUrl" value="${databasedev.url}"/>
    <property name="user" value="${databasedev.username}"/>
    <property name="password" value="${databasedev.password}"/>

    <property name="initialPoolSize" value="5" />
    <property name="minPoolSize" value="5" />
    <property name="maxPoolSize" value="1000" />
    <property name="acquireIncrement" value="5" />
    <property name="maxStatements" value="1000" />
    <property name="maxStatementsPerConnection" value="1000"/>
    <property name="maxIdleTime" value="10800"/> <!-- 3 hours -->
</bean>

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
    <constructor-arg>
         <ref bean="dataSourceDev" />
    </constructor-arg>
</bean>

<bean id="someDaoBean" class="com.gedi.platform.dao.SomeDaoClass">
    <property name="jdbcTemplate" ref="jdbcTemplate" />
</bean>

<bean id="someResourceClass" class="com.gedi.platform.SomeResourceClass">
    <property name="someDao" ref="someDaoBean" />
</bean>

You can see that it's a Java EE web application - it uses Jetty as its application server. My question is, how does Jetty instantiate our beans, and how will that affect connection pooling? If we have dozens of users using the web site at different times, will all of these users be placed in the same connection pool? Or is there only one connection pool per client, in which every HTTP client creates new instances of Resource, DAO, JdbcTemplate and C3P0?

Am I being clear? What I want to have is one connection pool for all HTTP requests, regardless of whether they come from web browsers originating in Boston or New Zealand. That way, the connection pool is exerting its maximum effects. However, if a new connection pool is instantiated for every HTTP client, then the pooling doesn't end up being much of an improvement.

Edit

An important tidbit - We use the Jersey reference implementation of JAX-RS to produce a RESTful interface. So our servlet dispatches requests through Jersey which finds a suitable Resource class/method to handle them. I wonder whether Jersey re-instantiates these classes on every request, or keeps one instance of them at all times.

Upvotes: 1

Views: 185

Answers (2)

Tomasz Nurkiewicz
Tomasz Nurkiewicz

Reputation: 340923

Neither Jersey nor Jetty are relevant here. Spring is important here. And in Spring every bean (like your dataSourceDev, jdbcTemplate and someDaoBean) are singletons. That means when Spring application context starts, it will creatly exactly one instance of each of them.

That means no matter what uses your DataSource (web request, background job, etc.), the same instance (thus the same connection pool) is used. You are right that if connection pool was created per each request, it would not have been much of an improvement. Actually it would be much, much slower.

But in your case (and this is how 99% of web applications work) all code requiring database access will compete and reuse the same connections (or wait if none available). BTW make sure your database can actually handle 1000 concurrent connections.

Upvotes: 1

Varun Achar
Varun Achar

Reputation: 15109

Spring creates the beans and caches them, so unless you have specified the beans as prototype scoped(which creates a new bean for each request), all bean are singleton's by default. Jetty doesn't interfere.

When a request comes in, the DispatcherServlet catches the request and hands it off to the appropriate handler. The handler is the same bean if it has not been declared as a prototype bean.

You understood the connection pool correctly. This is exactly why the concept was created. It doesn't matter where the request came from, the maximum number of connections to the database at any point in time will be the one you have defined in the maxPoolSize property.

Upvotes: 1

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