Narayana team blog: Narayana JDBC integration for Tomcat

Narayana implements JTA specification in Java. It's flexible and easy to be integrated to any system which desires transaction capabilities. As proof of the Narayana extensibility check our quickstarts like Spring Boot one or Camel one.
But this blogpost is different integration effort. It talks in details about Narayana integration with Apache Tomcat server.

If you do not care about details then just jump directly to the Narayana quickstarts in this area and use the code there for yourself.

If you want more detailed understanding read further.
All the discussed abilities are considered as the state of Narayana 5.8.1.Final or later.

Narayana, database resources and JDBC interface

All the proclaimed Narayana capabilities to integrate with other systems come from requirements for the system to conform with the JTA specification. JTA expects manageable resources which follows XA specification in particular. For case of the database resources the underlaying API is defined by JDBC specification. JDBC assembled resources manageable by transaction manager under package javax.sql It defines interfaces used for managing XA capabilities. The probably most noticable is XADataSource which serves as factory for XAConnection. From there we can otain XAResource. The XAResource is interface that the transaction manager works with. The instance of it participates in the two phase commit.

The workflow is to get or create the XADataSource, obtains XAConnection and as next the XAResource which is enlisted to the global transaction (managed by a transaction manager). Now we can call queries or statements through the XAConnection. When all the business work is finished the global transaction is commanded to commit which is propagated to call the commit on each enlisted XAResources.

It's important to mention that developer is not expected to do all this (getting xa resources, enlisting them to transaction manager…) All this handling is responsibility of the "container" which could be WildFly, Spring or Apache Tomcat in our case.
Normally the integration which ensures the database XAResource is enlisted to the transaction is provided by some pooling library. By the term pooling library we means code that manages a connection pool with capability enlisting database resource to the transaction.

We can say at the high level that integration parts are

the Apache Tomcat container
Narayana library
jdbc pooling library

In this article we will talk about Narayana JDBC transactional driver, Apache Commons DBCP and IronJacamar.

Narayana configuration with Tomcat

After the brief overview of integration requirements, let's elaborate on common settings needed for any integration approach you choose.
Be aware that each library needs a little bit different configuration and especially IronJacamar is specific.

JDBC pooling libraries integration

Narayana provides integration code in maven module tomcat-jta. That contains the glue code which integrates Narayana to the world of the Tomcat. If you write an application you will need the following:

providing Narayana itself to the application classpath
providing Narayana tomcat-jta module to the application classpath
configure WEB-INF/web.xml with NarayanaJtaServletContextListener which ensures the intialization of Narayana transaction manager
add META-INF/context.xml which setup Tomcat to start using implementation of JTA interfaces provided by Narayana
configure database resources to be XA aware and cooperate with Narayana by setting them up in the META-INF/context.xml

NOTE: if you expect to use the IronJacamar this requirements differs a bit!

If we take a look at the structure of the jar to be deployed we would get the picture possibly similar to this one:

  ├── META-INF
  │   └── context.xml
  └── WEB-INF
      ├── classes
      │   ├── application…
      │   └── jbossts-properties.xml
      ├── lib
      │   ├── arjuna-5.8.1.Final.jar
      │   ├── jboss-logging-3.2.1.Final.jar
      │   ├── jboss-transaction-spi-7.6.0.Final.jar
      │   ├── jta-5.8.1.Final.jar
      │   ├── postgresql-9.0-801.jdbc4.jar
      │   └── tomcat-jta-5.8.1.Final.jar
      └── web.xml

From this summary let's overview the configuration files one by one to see what's needed to be defined there.

Configuration files to be setup for the integration

WEB-INF/web.xml


  <web-app>
    <listener>
        <listener-class>org.jboss.narayana.tomcat.jta.NarayanaJtaServletContextListener</listener-class>
    </listener>
  </web-app>

The web.xml needs to define the NarayanaJtaServletContextListener to be loaded during context initialization to initialize the Narayana itself. Narayana needs to get running, for example, reaper thread that ensures transaction timeouts checking or thread of recovery manager.

WEB-INF/clases/jbossts-properties.xml

This file is not compulsory. The purpose is to configure the Narayana itself.
If you don't use your own configuration file then the default is in charge. See more at blogpost Narayana periodic recovery of XA transactions or consider settings done by the default descriptor jbossts-properties.xml at narayana-jts-idlj.

META-INF/context.xml


  <?xml version="1.0" encoding="UTF-8" standalone="no"?>
  <Context antiJarLocking="true" antiResourceLocking="true">
      <!-- Narayana resources -->
      <Transaction factory="org.jboss.narayana.tomcat.jta.UserTransactionFactory"/>
      <Resource factory="org.jboss.narayana.tomcat.jta.TransactionManagerFactory"
        name="TransactionManager" type="javax.transaction.TransactionManager"/>
      <Resource factory="org.jboss.narayana.tomcat.jta.TransactionSynchronizationRegistryFactory"
        name="TransactionSynchronizationRegistry" type="javax.transaction.TransactionSynchronizationRegistry"/>

      <Resource auth="Container" databaseName="test" description="Data Source"
        factory="org.postgresql.xa.PGXADataSourceFactory" loginTimeout="0"
        name="myDataSource" password="test" portNumber="5432" serverName="localhost"
        type="org.postgresql.xa.PGXADataSource" user="test" username="test"
        uniqueName="myDataSource" url="jdbc:postgresql://localhost:5432/test"/>
      <Resource auth="Container" description="Transactional Data Source"
        factory="org.jboss.narayana.tomcat.jta.TransactionalDataSourceFactory"
        initialSize="10" jmxEnabled="true" logAbandoned="true" maxAge="30000"
        maxIdle="16" maxTotal="4" maxWaitMillis="10000" minIdle="8"
        name="transactionalDataSource" password="test" removeAbandoned="true"
        removeAbandonedTimeout="60" testOnBorrow="true" transactionManager="TransactionManager"
        type="javax.sql.XADataSource" uniqueName="transactionalDataSource"
        username="test" validationQuery="select 1" xaDataSource="myDataSource"/>
  </Context>

I divide explanation this file into two parts. First are the generic settings - those needed for transaction manager integration (top part of the context.xml). The second part is on resource declaration that defines linking to the JDBC pooling library.

Transaction manager integration settings

We define implementation classes for the JTA api here. The implementation is provided by Narayana transaction manager. Those are lines of UserTransactionFactory and resources of TransactionManager and TransactionSynchronizationRegistry in the context.xml file.

JDBC pooling library settings

We aim to define database resources that can be used in the application. That's how you get the connection typically with code DataSource ds = InitialContext.doLookup("java:comp/env/transactionalDataSource"), and eventually execute a sql statement.
We define a PostgreSQL datasource with information how to create a new XA connection (we provide the host and port, credentials etc.) in the example.
The second resource is definition of jdbc pooling library to utilize the PostgreSQL one and to provide the XA capabilities. It roughtly means putting the PostgreSQL connection to the managed pool and enlisting the work under an active transaction.
Thus we have got two resources defined here. One is non-managed (the PosgreSQL one) and the second manages the first one to provide the ease work with the resources. For the developer is the most important to know he needs to use the managed one in his application, namely the transactionalDataSource from our example.

A bit about datasource configuration of Apache Tomcat context.xml

Let's take a side step at this place. Before we will talk in details about supported pooling libraries let's check a little bit more about the configuration of the Resource from perspective of XA connection in the context.xml.

Looking at the Resource definition there are highlighted parts which are interesting for us

  <Resource auth="Container" databaseName="test" description="Data Source"
    factory="org.postgresql.xa.PGXADataSourceFactory"
    loginTimeout="0" name="myDataSource" password="test" portNumber="5432" serverName="localhost"
    type="org.postgresql.xa.PGXADataSource" uniqueName="myDataSource"
    url="jdbc:postgresql://localhost:5432/test" user="test" username="test"/>

name: defines the name the resource is bound at the container and we can use the jndi lookup to find it by that name in application
factory: defines what type we will get as the final created Object. The factory which we declares here is class which implements interface ObjectFactory and from the provided properties it construct an object.
If we would not define any factory element in the definition then the Tomcat class ResourceFactory is used (see default factory constants). The ResourceFactory will pass the call to the BasicDataSourceFactory of the dbcp2 library. Here we can see the importantce of the type xml parameter which defines what is the object type we want to obtain and the factory normally checks if it's able to provide such (by string equals check usually).
The next step is generation of the object itself where the factory takes each of the properties and tries to applied them.
In our case we use the PGXADataSourceFactory which utilizes some of the properties to create the XADataSource.
serverName, portNumber, databaseName, user, password: are properties used by the object factory class to get connection from the database
Knowing the name of the properties for the particular ObjectFactory is possibly the most important when you need to configure your datasource. Here you need to check setters of the factory implementation.
In case of the PGXADataSourceFactory we need to go through the inheritance hierarchy to find the properties are saved at BaseDataSource. For our case for the relevant properties are user name and password. From the BaseDataSource we can see the setter for the user name is setUser thus the property name we look for is user.

After this side step let's take a look at the setup of the Resources in respect of the used pooling library.

Apache Commons DBCP2 library

Quickstart: https://github.com/jbosstm/quickstart/tree/master/dbcp2-and-tomcat

The best integration comes probably with Apache Common DBCP2 as the library itself is part of the Tomcat distribution (the Tomcat code base uses fork of the project). The XA integration is provided in Apache Tomcat version 9.0.7 and later. There is added dbcp2 package managed which knows how to enlist a resource to XA transaction.

The integration is similar to what we discussed in case of the JDBC transactional driver. You need to have configured two resources in context.xml. One is the database datasource (see above) and other is wrapper providing XA capabilities.


  <Resource name="transactionalDataSource" uniqueName="transactionalDataSource"
    auth="Container" type="javax.sql.XADataSource"
    transactionManager="TransactionManager" xaDataSource="h2DataSource"
    factory="org.jboss.narayana.tomcat.jta.TransactionalDataSourceFactory"/>

The integration is here done over the use of the specific factory which directly depends on classes from Apache Tomcat org.apache.tomcat.dbcp.dbcp2 package. The factory ensures the resource being enlisted to the recovery manager as well.
The nice feature is that you can use all the DBCP2 configuration parameters for pooling as you would used when BasicDataSource is configured. See the configuration options and the their meaning at the Apache Commons documentation.

Summary:

Already packed in the Apache Tomcat distribution from version 9.0.7
Configure two resources in context.xml. One is the database datasource, the second is wrapper providing XA capabilities with use of the dbcp2 pooling capabilities integrated with TransactionalDataSourceFactory.

NOTE: if you consider checking the pool status over JMX calls then DBCP2 comes with BasicDataSourceMXBean which exposes some information about the pool. You need to provide jmxName in your context.xml.


  <Resource name="transactionalDataSource" uniqueName="transactionalDataSource"
    auth="Container" type="javax.sql.XADataSource"
    transactionManager="TransactionManager" xaDataSource="h2DataSource"
    jmxEnabled="true" jmxName="org.apache.commons.dbcp2:name=transactionalDataSource"
    factory="org.jboss.narayana.tomcat.jta.TransactionalDataSourceFactory"/>

Narayana jdbc transactional driver

Quickstart: https://github.com/jbosstm/quickstart/tree/master/transactionaldriver/transactionaldriver-and-tomcat

With this we will get back to other two recent articles about jdbc transactional driver and recovery of the transactional driver.
The big advantage of jdbc transactional driver is its tight integration with Narayana. It's the dependecy of the Narayana tomcat-jta module which contains all the integration code needed for Narayana working in Tomcat. So if you take the tomcat-jta-5.8.1.Final you have packed the Narayna integration code and jdbc driver in out-of-the-box working bundle.

Configuration actions

Here we will define two resources in the context.xml file. The first one is the database one.


  <Resource name="h2DataSource" uniqueName="h2Datasource" auth="Container"
    type="org.h2.jdbcx.JdbcDataSource" username="sa" user="sa" password="sa"
    url="jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1" description="H2 Data Source"
    loginTimeout="0" factory="org.h2.jdbcx.JdbcDataSourceFactory"/>

The database one defines data needed for preparation of datasource and creation of the connection. The datasource is not XA aware. We need to add one more layer on top which is transactional JDBC driver here. It wraps the datasource connection within XA capabilities.


  <Resource name="transactionalDataSource" uniqueName="transactionalDataSource"
    auth="Container" type="javax.sql.DataSource" username="sa" password="sa"
    driverClassName="com.arjuna.ats.jdbc.TransactionalDriver"
    url="jdbc:arjuna:java:comp/env/h2DataSource" description="Transactional Driver Datasource"
    connectionProperties="POOL_CONNECTIONS=false"/>

As we do not define the element factory then the default one is used which is org.apache.tomcat.dbcp.dbcp2.BasicDataSourceFactory. Unfortunately, this is fine up to the time you need to process some more sophisticated pooling strategies. In this aspect the transactional driver does not play well with the default factory and some further integration work would be needed.

This configuration is nice for having transactionalDataSource available for the transactional work. Unfortunately, it's not all that you need to do. You miss here configuration of recovery. You need to tell the recovery manager what is the resource to care of. You can setup this in jbossts-properties.xml or maybe easier way to add it to environment variables of the starting Tomcat, for example by adding the setup under script $CATALINA_HOME/bin/setenv.sh
You define it with property com.arjuna.ats.jta.recovery.XAResourceRecovery.


-Dcom.arjuna.ats.jta.recovery.XAResourceRecovery1=com.arjuna.ats.internal.jdbc.recovery.BasicXARecovery;abs://$(pwd)/src/main/resources/h2recoveryproperties.xml

You can define whatever number of the resources you need the recovery is aware of. It's done by adding more numbers at the end of the property name (we use 1 in the example above). The value of the property is the class implementing com.arjuna.ats.jta.recovery.XAResourceRecovery. All the properties provided to the particular implementation is concatenated after the ; character. In our example it's path to the xml descriptor h2recoveryproperties.xml.
When transactional driver is used then you need to declareBasicXARecovery as recovery implementation class and this class needs connection properties to be declared in the xml descriptor.


  <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
  <entry key="DB_1_DatabaseUser">sa</entry>
  <entry key="DB_1_DatabasePassword">sa</entry>
  <entry key="DB_1_DatabaseDynamicClass"></entry>
  <entry key="DB_1_DatabaseURL">java:comp/env/h2DataSource</entry>
</properties>

Note: there is option not defining the two resources under context.xml and use the env property for recovery enlistment. All the configuration properties are then involved in one properties file and transactional driver dynamic class is used. If interested the working example is at ochaloup/quickstart-jbosstm/tree/transactional-driver-and-tomcat-dynamic-class.

Summary:

Already packed in the tomcat-jta artifact
Configure two resources in context.xml. One is database datasource, the second is transactional datasource wrapped by transactional driver.
Need to configure recovery with env variable setup com.arjuna.ats.jta.recovery.XAResourceRecovery while providing xml descriptor with connection parameters

IronJacamar

Quickstart: https://github.com/jbosstm/quickstart/tree/master/jca-and-tomcat

The settings of IronJacamar integration differs pretty much from what we've seen so far. The IronJacamar implements whole JCA specification and it's pretty different beast (not just a jdbc pooling library).

The whole handling and integration is passed to IronJacamar itself.
You don't use tomcat-jta module at all.
You need to configure all aspects in the IronJacamar xml descriptors. Aspects like datasource definition, transaction configuration, pooling definition, up to the jndi binding.

The standalone IronJacamar is needed to be started with command org.jboss.jca.embedded.EmbeddedFactory.create().startup() where you defines the descriptors to be used. You can configure it in web.xml as ServletContextListener.

What are descriptors to be defined:

jdbc-xa.rar which is resource adapter provided by IronJacamar itself. It needs to be part of the deployment. It's capable to process ds files.
ds.xml which defines connecion properties and jndi name binding
transaction.xml which configures transaction manager instead of use of the jbossts-properties.xml.

Check more configuration in IronJacamar documentation.

Summary: IronJacamar is started as embedded system and process all the handling on its own. Developer needs to provide xml descriptor to set up.

Summary

This article provides the details about configuration of the Narayana when used in Apache Tomcat container. We've seen the three possible libraries to get the integration working - the Narayana JDBC transactional driver, Apache DBCP2 library and IronJacamar JCA implementation.
On top of it, the article contains many details about Narayana and Tomcat resource configuration.

If you hesitate what alternative is the best fit for your project then this table can help you

JDBC integration library	When to use
Apache DBCP2	It's the recommended option when you want to obtain Narayana transaction handling in the Apache Tomcat Integration is done in the Narayana resource factory which ensures easily setting up the datasource and recovery in the one step.
Narayana transactional jdbc driver	Is good fit when you want to have all parts integrated and covered by Narayana project. It provides lightweight JDBC pooling layer that could be nice for small projects. Integration requires a little bit more hand working.
IronJacamar	To be used when you need whole JCA functionality running in Apache Tomcat. The benefit of this solution is the battle tested integration of Narayana and IronJacamar as they are delivered as one pack in the WildFly application server.

Monday, May 21, 2018

Narayana JDBC integration for Tomcat