[JBoss jBPM] - Re: job executor explained in a nutshell
by kadlecp
Hello,
I was thinking about REPEATABLE_READ isolation level with optimistic locking and it seems to me that it can not work. In docs there is written that
anonymous wrote : Non-Repeatable reads are a problem for optimistic locking and therefore isolation level READ_COMMITTED is not enough cause it allows for Non-Repeatable reads to occur. So REPEATABLE_READ is required if you configure more than one job executor thread.
|
But I found here http://www.avaje.org/occ.html that
anonymous wrote : It is important to note that Optimistic Concurrency Checking only works in READ_COMMITED Transaction Isolation Level. Specifically, at higher Isolation levels such as SERIALIZABLE the UPDATE or DELETE will see the database as at the Transaction start time. In the time gap between Transaction start time and the UPDATE/DELETE statement there could be commited changes that will be lost (Lost Updates).
I think b.) is right, it makes sense.
jBPM docs are not correct, am I right? Your docs confused me.
Pavel
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18 years, 1 month
[JBoss Messaging] - Re: JBoss Messaging and Spring Message Listener Container
by jamesbo
I've done a proof-of-concept necessitated by http://www.jboss.com/index.html?module=bb&op=viewtopic&t=136956 using Spring's JmsMessageEndpointManager.
I started testing by bootstrapping via applicationContext.xml as documented by Spring then did the equivalent in code (because we need dynamic configuration). This has worked fine so far.
One problem I had was http://jira.jboss.com/jira/browse/JBAS-5623 so implemented following as workaround:
/**
| * Customised partly to work around http://jira.jboss.com/jira/browse/JBAS-5623 and partly to provide support
| * for SESSION_TRANSACTED. By default Spring would override this to AUTO_ACKNOWLEDGE although JBoss would
| * ignore that so long as its 'sessionTransacted' property remained true (the default value).
| */
| public class JBossJmsActivationSpecFactory extends StandardJmsActivationSpecFactory {
|
| @Override
| protected void applyAcknowledgeMode(BeanWrapper bw, int ackMode) {
| if (bw.isWritableProperty("acknowledgeMode")) {
| switch (ackMode) {
| case Session.AUTO_ACKNOWLEDGE:
| bw.setPropertyValue("acknowledgeMode", "AUTO_ACKNOWLEDGE");
| break;
| case Session.DUPS_OK_ACKNOWLEDGE:
| bw.setPropertyValue("acknowledgeMode", "DUPS_OK_ACKNOWLEDGE");
| break;
| case Session.SESSION_TRANSACTED:
| bw.setPropertyValue("acknowledgeMode", "SESSION_TRANSACTED");
| break;
| default:
| throw new IllegalArgumentException("acknowledgeMode = " + ackMode + " not supported.");
| }
|
| }
| }
|
| }
So POJO MessageListener looks OK. I was able to confirm that Transactional messaging was now working, the callback is on a proper WorkManager Thread and we can dynamically create, start and stop connections.
Here's config from initial test:
<?xml version="1.0" encoding="UTF-8"?>
| <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
| xmlns:jee="http://www.springframework.org/schema/jee" xmlns:util="http://www.springframework.org/schema/util"
| xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
| http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.5.xsd
| http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.5.xsd">
|
| <bean id="mbeanServer" class="org.jboss.mx.util.MBeanServerLocator" factory-method="locateJBoss" />
|
| <bean id="resourceAdapter" factory-bean="mbeanServer" factory-method="getAttribute">
| <constructor-arg>
| <bean class="org.springframework.jmx.support.ObjectNameManager" factory-method="getInstance">
| <constructor-arg value="jboss.jca:name='jms-ra.rar',service=RARDeployment" />
| </bean>
| </constructor-arg>
| <constructor-arg value="ResourceAdapter" />
| </bean>
|
| <bean id="messageListener" class="jca.jms.MessageLogger" />
|
| <bean id="jmsManager" class="org.springframework.jms.listener.endpoint.JmsMessageEndpointManager"
| lazy-init="true">
| <property name="activationSpecFactory">
| <bean class="jca.jms.config.JBossJmsActivationSpecFactory">
| <property name="activationSpecClass" value="org.jboss.resource.adapter.jms.inflow.JmsActivationSpec" />
| </bean>
| </property>
| <property name="activationSpecConfig">
| <bean class="org.springframework.jms.listener.endpoint.JmsActivationSpecConfig">
| <property name="destinationName" value="MYTOPIC" />
| <property name="pubSubDomain" value="true" />
| <property name="acknowledgeMode">
| <util:constant static-field="javax.jms.Session.SESSION_TRANSACTED" />
| </property>
| </bean>
| </property>
| <property name="autoStartup" value="false" />
| <property name="resourceAdapter" ref="resourceAdapter" />
| <property name="messageListener" ref="messageListener" />
| </bean>
|
| </beans>
And code equivalent:
public class ControlEJB extends AbstractStatelessSessionBean {
|
| private static final String FACTORY_SELECTOR = "classpath*:beanRefFactory.xml";
| private static final String FACTORY_KEY = "jca-jms";
|
| private static final Logger log = Logger.getLogger(ControlEJB.class);
|
| private JmsMessageEndpointManager jmsManager;
|
| public void start() {
| log.info("#start");
| jmsManager.start();
| }
|
| public void stop() {
| log.info("#stop");
| jmsManager.stop();
| }
|
| @Override
| public void setSessionContext(SessionContext sessionContext) {
| super.setSessionContext(sessionContext);
| setBeanFactoryLocator(ContextSingletonBeanFactoryLocator.getInstance(FACTORY_SELECTOR));
| setBeanFactoryLocatorKey(FACTORY_KEY);
| }
|
| @Override
| protected void onEjbCreate() throws CreateException {
| log.info("#onEjbCreate");
| jmsManager = new JmsMessageEndpointManager();
|
| JmsActivationSpecConfig activationSpecConfig = new JmsActivationSpecConfig();
| activationSpecConfig.setAcknowledgeMode(Session.SESSION_TRANSACTED);
| activationSpecConfig.setDestinationName("MYTOPIC");
| activationSpecConfig.setPubSubDomain(true);
| jmsManager.setActivationSpecConfig(activationSpecConfig);
|
| StandardJmsActivationSpecFactory activationSpecFactory = new JBossJmsActivationSpecFactory();
| try {
| activationSpecFactory.setActivationSpecClass(Class
| .forName("org.jboss.resource.adapter.jms.inflow.JmsActivationSpec"));
| } catch (ClassNotFoundException e) {
| throw new EJBException(e);
| }
| jmsManager.setActivationSpecFactory(activationSpecFactory);
|
| jmsManager.setAutoStartup(false);
| jmsManager.setResourceAdapter((ResourceAdapter) getBeanFactory().getBean("resourceAdapter"));
|
| MessageListener listener = new MessageLogger();
| jmsManager.setMessageListener(listener);
| try {
| jmsManager.afterPropertiesSet();
| } catch (ResourceException e) {
| throw new EJBException(e);
| }
| }
|
| }
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18 years, 1 month