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Re: Failed to acquire the pool semaphore in empty pool
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created by <a href="https://community.jboss.org/people/garrydias">Garry Dias</a> in <i>EJB3</i> - <a href="https://community.jboss.org/message/760376#760376">View the full discussion</a>
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<div class="jive-rendered-content"><p>Yes. I´m still writing a post with a sequence diagram to explain better.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>To be short:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>At the line where I worte <code class="jive-code jive-java"><span style="color: darkgreen;">// A JMSConsumer is created to retrieve exchange object when MDB end </span></code>there´s lot of statements and one of that is a call to javax.jms.MessageConsumer.receive() method. However, when the producer sent the message it set a Time To Live in my jms message. This TTL was 20 seconds. As my MDB connect to a third party webService that hangs more than 30 seconds sometimes, my jms message died before MDB acks the comsumption. Meanwhile, the javax.jms.MessageConsumer.receive() method is waiting for a message that should never come because the jms message relies in DLQ now. So, javax.jms.MessageConsumer.receive() method will wait forever and an available <code class="jive-code jive-java">MyWorkerBean </code>instance in my pool (annotated as <code class="jive-code jive-java">@Pool(value = PoolDefaults.POOL_IMPLEMENTATION_STRICTMAX, maxSize = 30)</code>) will be decreased. You can see this decreasing in jmx-console, menu j2ee.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The solution was set a TTL for MessageConsumer.receive() method. So today my code looks like this:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><code class="jive-code jive-java">@Clustered<br/>@Local(MyWorkerInterface.class)<br/>@Stateless(name = <span style="color: red;">"MyWorkerBean"</span>)<br/>@Interceptors(value = <span style="color: navy;">{</span> SpringBeanAutowiringInterceptor.class, LoggingInterceptor.class <span style="color: navy;">}</span>)<br/>@RolesAllowed(value = <span style="color: red;">"client"</span>)<br/>@Pool(value = PoolDefaults.POOL_IMPLEMENTATION_STRICTMAX, maxSize = 30)<br/><span style="color: navy;"><strong>public</strong></span> <span style="color: navy;"><strong>class</strong></span> MyWorkerBean <span style="color: navy;"><strong>implements</strong></span> MyWorkerInterface <span style="color: navy;">{</span><br/> <br/>    @RolesAllowed(<span style="color: red;">"client"</span>)<br/>    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)<br/>    <span style="color: navy;"><strong>public</strong></span> WorkResponse execute(<span style="color: navy;"><strong>final</strong></span> WorkRequest workRequest) <span style="color: navy;">{</span><br/> <br/>        <span style="color: navy;"><strong>long</strong></span> start = System.currentTimeMillis();<br/> <br/>        WorkExchange exchange = <span style="color: navy;"><strong>new</strong></span> WorkExchange();<br/>        exchange.setWorkRequest(workRequest);<br/> <br/>        <span style="color: darkgreen;">// A JMSProducer is created to send exchange to a JMS queue</span><br/>        <span style="color: darkgreen;">// A MDB class retrieve data from a third party webservice (expensive operation taking between 300 to 60000ms to finish) using WorkExchange.workRequest fields</span><br/>        ...</code></p><p>                 <code class="jive-code jive-java">ObjectMessage responseMessage</code> = (<code class="jive-code jive-java">ObjectMessage</code>) <code class="jive-code jive-java">messageConsumer.receive(20000);</code> </p><p><code class="jive-code jive-java">        ... </code></p><p><code class="jive-code jive-java"><br/>        LoggerUtil.info(<span style="color: red;">"Operation time: "</span> + (System.currentTimeMillis() - start));<br/> <br/>        <span style="color: darkgreen;">// WorkExchange.workResponse have been set by MDB</span><br/>        WorkResponse response = exhange.getWorkResponse();<br/> <br/>        <span style="color: navy;"><strong>return</strong></span> response;<br/>    <span style="color: navy;">}</span><br/><span style="color: navy;">}</span></code></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="color: navy;">[]s<br/></span></p></div>
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