Deadlock in DbIdGenerator

[exp2345]

This is a follow up to http://forums.activiti.org/comment/25407. I have posted in the Activiti Engine forum because I have reproduced the issue without explorer. See the linked thread for a simple process the reproduces the problem.

When there are a large number of jobs queued in the system occasionally two or more threads get stuck waiting indefinitely. The issue occurs more frequently when the process engine is shut down and restarted while jobs are queued. The issue occurs when a single instance of a process engine is running (not clustered).

The Spring config used for the engine is pasted below, and the thread dump is attached.

<?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:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
   xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jee="http://www.springframework.org/schema/jee"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
       http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.1.xsd">


    <bean id="jerseyClientFactory" class="com.CLIENT.bw2.util.JerseyClientFactory"/>
    <bean id="jerseyClient" class="com.sun.jersey.api.client.Client" factory-bean="jerseyClientFactory" factory-method="create"/>

     <context:component-scan base-package="com.CLIENT.bw2.service"  />

    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="${CLIENT.yml.config}" />
        <property name="propertiesPersister" ref="myYamlPersister" />
        <!– Allow other PropertyPlaceholderConfigurer to run as well –>
        <property name="ignoreUnresolvablePlaceholders" value="true"/>
    </bean>
    <bean id="myYamlPersister" class="com.CLIENT.spring.YamlPropertiesPersister"></bean>

  <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
    <property name="driverClassName" value="${database.driverClass}" />
    <property name="url" value="${database.url}" />
    <property name="username" value="${database.user}" />
    <property name="password" value="${database.password}" />
    <property name="defaultAutoCommit" value="false" />
  </bean>

  <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
     <property name="dataSource" ref="dataSource" />
  </bean>
  
  <bean id="processEngineConfiguration" class="org.activiti.spring.SpringProcessEngineConfiguration">
    <property name="history" value="audit" />
     <property name="dataSource" ref="dataSource" />
     <property name="transactionManager" ref="transactionManager" />
     <property name="databaseSchemaUpdate" value="true" />
    <property name="jobExecutor" ref="jobExecutor"/>
     <property name="jobExecutorActivate" value="true" />
    <!– TODO: had to comment out this line, not sure why –>
    <!–<property name="enableDatabaseEventLogging" value="true" />–>
      <!–<property name="deploymentResources" value="classpath*:/diagrams/*.bpmn" />–>
    <property name="customFormTypes">
      <list>
        <bean class="org.activiti.explorer.form.UserFormType"/>
        <bean class="org.activiti.explorer.form.ProcessDefinitionFormType"/> 
        <bean class="org.activiti.explorer.form.MonthFormType"/>   
      </list>
    </property>
      <property name="eventListeners">
          <list>
              <bean class="com.CLIENT.bw2.util.LoggingActivitiEventListener" />
          </list>
      </property>
  </bean>
  
  <bean id="processEngine" class="org.activiti.spring.ProcessEngineFactoryBean" destroy-method="destroy">
     <property name="processEngineConfiguration" ref="processEngineConfiguration" />
  </bean>
  
  <bean id="repositoryService" factory-bean="processEngine" factory-method="getRepositoryService" />
  <bean id="runtimeService" factory-bean="processEngine" factory-method="getRuntimeService" />
  <bean id="taskService" factory-bean="processEngine" factory-method="getTaskService" />
  <bean id="historyService" factory-bean="processEngine" factory-method="getHistoryService" />
  <bean id="managementService" factory-bean="processEngine" factory-method="getManagementService" />
  <bean id="identityService" factory-bean="processEngine" factory-method="getIdentityService" />
  <bean id="formService" factory-bean="processEngine" factory-method="getFormService" />
  
  <!–<bean id="activitiLoginHandler" class="org.activiti.explorer.ui.login.DefaultLoginHandler">–>
    <!–<property name="identityService" ref="identityService" />–>
  <!–</bean>–>

    <bean id="jobExecutor" class="org.activiti.engine.impl.jobexecutor.DefaultJobExecutor"/>

</beans>
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[trademak]

When you create a lot of process instances and tasks you could change the idBlockSize (which is 2500 by default) or you could use the StrongUuidGenerator IdGenerator instead of the default DbIdGenerator.

Best regards,

[exp2345]

Tijs,

Thanks for the suggestion. Based on my initial testing using the StrongUuidGenerator seems to fix the problem.