[[JTA_Reference]]
= JTA Reference

WildFly uses http://narayana.io[Narayana] as the implementation of the JTA specification.
Narayana manages transactions in the application server.

== Transactions in Enterprise Java applications

Transactions are one of the core functionalities provided by the container
for the applications. A developer can manage transactions either with
the programmatic approach - with API defined by JTA specification.
Or he can use annotations. There are two types.

* first - EJB annotations, their meaning and capabilities are defined under
  EJB specification and are valid when used in the EJB component
* second - CDI annotations, their meaning is defined under JTA specification

[[programmatic-jta]]
=== Transactions managed with programmatic JTA API

The JTA API is defined under
https://javaee.github.io/javaee-spec/javadocs/javax/transaction/package-summary.html[`javax.transaction`]
package. The package could be considered a bit misguiding as it presents classes
which are expected to be used by application developer. These classes
are intended as an API for the application server (as the WildFly is).

The user is expected to interact with
https://javaee.github.io/javaee-spec/javadocs/javax/transaction/UserTransaction.html[`javax.transaction.UserTransaction`]
which defines the transaction boundaries. The `UserTransaction` could be used
in case the transaction is not defined by annotation at the method
- aka. the transaction is not managed by the container. Those are places like
servlets, CDI bean which is not annotated with `@Transactional` and
EJBs defined as bean managed.

`UserTransaction` is available via CDI injection

[source,java,options="nowrap"]
----
@Inject
UserTransaction txn;
----

or with EJB `@Resource` injection where you can additionally define the JNDI
name to be looked-up. The specification says it's `java:comp/UserTransaction`.

[source,java,options="nowrap"]
----
@Resource(lookup = "java:comp/UserTransaction")
UserTransaction txn;
----

The code can then look like

[source,java,options="nowrap"]
----
@WebServlet(name="TestServlet", urlPatterns={"/"})
public class TestServlet extends HttpServlet {
    private static final Logger LOG = Logger.getLogger(TestServlet.class);

    @Inject
    private UserTransaction txn;

    @PersistenceContext
    private EntityManager em;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            txn.begin();

            em.persist(new TestEntity(1, "Mr. Transaction"));

            txn.commit();
          } catch (NotSupportedException beginExceptions) {
              LOG.errorf(beginExceptions, "Cannot start transaction: '%s'", txn);
          } catch (SecurityException | IllegalStateException | RollbackException
                  | HeuristicMixedException | HeuristicRollbackException commitExceptions) {
              LOG.errorf(commitExceptions, "Cannot commit transaction: '%s'", txn);
          } catch (SystemException systemException) {
              LOG.errorf(systemException, "Unexpected error condition on work with transaction: '%s'", txn);
          }
    }
}
----

https://javaee.github.io/javaee-spec/javadocs/javax/transaction/TransactionManager.html[`javax.transaction.TransactionManager`]
is not meant to be used by business logic but if you need to register
https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Synchronization.html[a synchronization]
or you need to change transaction timeout (before the `begin()` method is called)
then it will be the option for you.

The `TransactionManager` could be taken with injection
and looked-up with the JNDI name

[source,java,options="nowrap"]
----
@Inject
TransactionManager tm;

// or

@Resource(lookup = "java:/TransactionManager")
TransactionManager tm;
----

[[in-cdi]]
=== Transactions in CDI beans

If you start using CDI beans then you can manage transactions either programmatically
or you can use annotations.
The https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Transactional.html[`@Transactional`]
defines transaction boundaries
(start of the method starts the transaction, while the transaction is finished at its end).
If the method finishes sucessfully the transaction is committed.
If the transaction ends with `RuntimeException` then it's rolled-back.

When you define the method to be `@Transactional` you define the behaviour
of incoming (or non-existent) transactional context.
Please refer the to documentation for
https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Transactional.TxType.html[`Transactional.TxType`].

It's important to note that the `TxType` influences the transaction management
*only* when called with the managed CDI bean. If you call the method directly -
without the CDI container wraps the invocation then the `TxType` has no effect.

[source,java,options="nowrap"]
----
@RequestScope
public class MyCDIBean {
  @Inject
  MyCDIBean myBean;

  @Transactional(TxType.REQUIRED)
  public void mainMethod() {
    // CDI container does not wrap the invocation
    // no new transaction is started
    innerFunctionality();

    // CDI container starts a new transaction
    // the method uses TxType.REQUIRES_NEW and is called from the CDI bean
    myBean.innerFunctionality();
  }

  @Transactional(TxType.REQUIRES_NEW)
  private void innerFunctionality() {
    // some business logic
  }
}
----

NOTE: the exception handling could be influenced by attributes
      `rollbackOn` and `dontRollbackOn` (of the `@Transactional` annotation)

WARNING: if you use the `@Transactional` for managing transactions boundaries
         you won't be permitted to use the `UserTransaction` methods.
         If you do so you can expect a runtime exception being thrown.

The CDI introduces as well a new scope for use with transactions -
https://javaee.github.io/javaee-spec/javadocs/javax/ejb/SessionContext.html[`@TransactionScoped`].

[[in-ejbs]]
=== Transactions in EJBs

Transaction management in EJB is administered with two annotations:
https://javaee.github.io/javaee-spec/javadocs/javax/ejb/TransactionManagement.html[`@TransactionManagement`]
 https://javaee.github.io/javaee-spec/javadocs/javax/ejb/TransactionAttribute.html[`@TransactionAttribute`].

NOTE: you can define the same behaviour when you use the `ejb-jar.xml`
      descriptor instead of the annotations

The WildFly provides specific annotation `org.jboss.ejb3.annotation.TransactionTimeout`
which gives you the chance to change the transaction timeout for a particular bean/method.

NOTE: when you use message-driven bean then the `@TransactionTimeout` does not work
      and you need to define the timeout through the `@ActivationConfigProperty`:
      `@ActivationConfigProperty(propertyName="transactionTimeout", propertyValue="1")`

The default behaviour of an EJB is to be

* container managed - transaction boundaries are driven by annotations
* when the EJB method is invoked - a new transaction is started when no transaction context is available,
or the method joins the existing transactions when the transaction context is passed by the call

It's the same transactional behaviour as if the EJB is annotated with

[source,java,options="nowrap"]
----
@TransactionManagement(TransactionManagementType.CONTAINER)
@TransactionAttribute(TransactionAttributeType.REQUIRED)
----

==== Container managed transactions

Using the `@TransactionManagement(TransactionManagementType.CONTAINER)` means
the container is responsible to manage transactions. The boundary of the transaction
is defined by the start and end of the method and you influence the behaviour by using
https://javaee.github.io/javaee-spec/javadocs/javax/ejb/TransactionAttribute.html[`@TransactionAttribute`].

If `java.lang.RuntimeException` is thrown the transaction is rolled back.
https://javaee.github.io/javaee-spec/javadocs/javax/ejb/EJBContext.html[EJBContext]
could be used to define the transaction should be rolled-back
by the end of the method when `setRollbackOnly` is used.

[source,java,options="nowrap"]
----
@Stateless
public class MyBean {
  @PersistenceContext
  private EntityManager em;

  @Resource
  EJBContext ctx;

  public void method() {
    em.persist(new TestEntity());
    // at the end of the method the rollback is called
    ctx.setRollbackOnly();
  }
}
----

NOTE: the `EJBContext` let you get the `UserTransaction` but you are not allowed
      to do any operation with that when you run container managed transaction.
      You can expect to receive a runtime exception in such case.

==== Bean managed transactions

Using the `@TransactionManagement(TransactionManagementType.BEAN)` means
the transaction will be managed manually with the use of the JTA API.
That's with the `UserTransaction` injections and methods on it.
You can inject the `EJBContext` to get the `UserTransaction` instance too.

NOTE: if a call is made from the container-managed method,
      passing the transaction context to the bean managed method
      then the context is suspended. It's similar(!) to
      call transaction managed bean annotated with
      `@TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)`

==== Transaction synchronization

JTA API gives a chance to react to the event of a finishing transaction.
The definition says that transaction manager announces the even of `beforeCompletion` and `afterCompletion`
which are defined by the interface https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Synchronization.html[javax.transaction.Synchronization].
The https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Synchronization.html#beforeCompletion--[`beforeCompletion`]
callback is invoked at time the transaction manager starts to commit the global transaction. The invocation is processed in the transaction context.
The https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Synchronization.html#afterCompletion-int-[`afterCompletion`]
is invoked after the transaction is committed or rolled-back (and is processed outside of the transaction context).

The user needs just to create a simple Java POJO and implement the interface.

[source,java,options="nowrap"]
----
public class MySynchronization
        implements javax.transaction.Synchronization {
  @Override
  public void beforeCompletion() {
    System.out.println("Transaction is about to be finished"):
  }

  @Override
  public void afterCompletion(int status) {
    System.out.println("Transaction finished with status " + status):
  }
}
----

For registration of the synchronization callback, the user can inject the
https://docs.oracle.com/javaee/7/api/javax/transaction/TransactionSynchronizationRegistry.html[javax.transaction.TransactionSynchronizationRegistry].
(the mandated JNDI location for the object is at `java:comp/TransactionSynchronizationRegistry`) and then to register
the synchronization instance. The instance is bound to the currently active transaction.

[source,java,options="nowrap"]
----
@Resource
TransactionSynchronizationRegistry transactionSynchronizationRegistry;

public void method() {
  transactionSynchronizationRegistry
    .registerInterposedSynchronization(new MySynchronization());
}
----

The transaction synchronization registry adds other useful methods which are `putResource(Object key, Object value)`
and `getResource(Object key)`. Their purpose is saving data objects alongside the transaction context.
When the transaction is active you can store and retrieve the saved data. When the transaction is finished
and there is no transaction context available (e.g. at `afterCompletion`) the `java.lang.IllegalStateException`
is thrown.

The other option for the user is to use https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Transaction.html[the transaction object]
to register the synchronization.

[source,java,options="nowrap"]
----
@Resource(lookup = "java:/TransactionManager")
TransactionManager tm;

public void method() {
tm.getTransaction().registerSynchronization(new MySynchronization());
----

When the user runs the Stateful Session Bean he can implement
interface https://javaee.github.io/javaee-spec/javadocs/javax/ejb/SessionSynchronization.html[javax.ejb.SessionSynchronization]
(or to use annotations) for the definition of the synchronization callbacks onto the bean.
The session synchronization defines three methods.
Of these three methods `afterBegin` is not connected to the transaction synchronization so we will not discuss it further.
The  following example works with annotations but the bean may just implement the `SessionSynchronization`
interface and it would work the same way.

[source,java,options="nowrap"]
----
// only(!) SFSB can use the capability of SessionSynchronization
@Stateful
public class MyStatefulBean {
  public void method() {
    System.out.println("Running an important business logic...");
    Thread.sleep(42000);
  }

  @BeforeCompletion
  public void beforeCompletion() {
    System.out.println("Transaction is about to be finished"):
  }

  @AfterCompletion
  public void afterCompletion(boolean committed) {
    System.out.println("Transaction finished with the outcome "
      + (committed ? "committed" : "rolled-back")):
  }
}
----

NOTE: for more information about CDI and registration of transaction synchronization
      look at https://jbossts.blogspot.com/2019/04/jta-and-cdi-integration.html[the article about Narayana integration of CDI events].

[[classloading]]
== Transactions subsystem class loading

The WildFly classloading is based
on the https://github.com/jboss-modules/jboss-modules[jboss modules]
which define the modular class loading system.
The transactions for CDI comes as the extension and because of it
this extension has to be available at the application classpath.
If the application/deployment uses annotations `@Transactional`
or `@TransactionScoped` then class loading handling is done automatically.

There is one limitation with the CDI with this approach.
If your application adds the transactional annotations dynamically
(you adds the annotations dynamically during runtime) then the
transaction module has to be
https://docs.jboss.org/author/display/WFLY/Class+Loading+in+WildFly[explicitly added]
to the application classpath.

This can be done with creating `META-INF/MANIFEST.MF` or
with use of `jboss-deployment-structure.xml` descriptor. The `MANIFEST.MF`
could look like

[source]
----
Manifest-Version: 1.0
Dependencies: org.jboss.jts export services
----

[[troubleshooting]]
== Transactions troubleshooting

The Narayana component is configured to log only messages with level `WARN`
(see category `com.arjuna` in the `standalone-*.xml`).
If you struggle issues of the transactional handling
you can get a better insight into transaction processing by setting the level to `TRACE`.

```bash
/subsystem=logging/logger=com.arjuna:write-attribute(name=level,value=TRACE)
```

The `TRACE` could overwhelm you with information from the transactions subsystem.
Let's quickly review what are the most important points to look at in the log.

NOTE: It's beneficial to understand how
      the https://developer.jboss.org/wiki/TwoPhaseCommit2PC[two-phase commit] works.

An example of the log messages produces by Narayana is (the content is shortened for sake of brevity)

```
[section 1]
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.jta] (default task-1) BaseTransaction.begin
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) StateManager::StateManager( 2, 0 )
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::BasicAction()
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::Begin() for action-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::actionInitialise() for action-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) ActionHierarchy::ActionHierarchy(1)
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) ActionHierarchy::add(0:ffff0a28050c:-a09a5fe:5c598d64:3b, 1)
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::addChildThread () action 0:ffff0a28050c:-a09a5fe:5c598d64:3b adding Thread[default task-1,5,main]
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::addChildThread () action 0:ffff0a28050c:-a09a5fe:5c598d64:3b adding Thread[default task-1,5,main] result = true
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) TransactionReaper::insert ( BasicAction: 0:ffff0a28050c:-a09a5fe:5c598d64:3b status: ActionStatus.RUNNING, 300 )
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.arjuna] (default task-1) ReaperElement::ReaperElement ( BasicAction: 0:ffff0a28050c:-a09a5fe:5c598d64:3b status: ActionStatus.RUNNING, 300 )
2019-02-05 14:19:39,745 TRACE [com.arjuna.ats.jta] (default task-1) TransactionImple.registerSynchronization - Class: class org.wildfly.transaction.client.AbstractTransaction$AssociatingSynchronization HashCode: 1114413551 toString: org.wildfly.transaction.client.AbstractTransaction$AssociatingSynchronization@426c99ef


[section 2]
TRACE [com.arjuna.ats.jta] (default task-1) TransactionImple.enlistResource ( TestXAResource(TestXAResourceCommon(id:944, xid:null, timeout:299, prepareReturn:0)) )
TRACE [com.arjuna.ats.jta] (default task-1) TransactionImple.getStatus: javax.transaction.Status.STATUS_ACTIVE
TRACE [com.arjuna.ats.arjuna] (default task-1) OutputObjectState::OutputObjectState()
TRACE [com.arjuna.ats.arjuna] (default task-1) FileSystemStore.write_committed(0:ffff0a28050c:-a09a5fe:5c598d64:43, EISNAME)
TRACE [com.arjuna.ats.arjuna] (default task-1) ShadowingStore.write_state(0:ffff0a28050c:-a09a5fe:5c598d64:43, EISNAME, StateType.OS_ORIGINAL)
TRACE [com.arjuna.ats.arjuna] (default task-1) ShadowingStore.genPathName(0:ffff0a28050c:-a09a5fe:5c598d64:43, EISNAME, StateType.OS_ORIGINAL)
TRACE [com.arjuna.ats.arjuna] (default task-1) FileSystemStore.genPathName(0:ffff0a28050c:-a09a5fe:5c598d64:43, EISNAME, 11)
TRACE [com.arjuna.ats.arjuna] (default task-1) FileSystemStore.openAndLock(data/tx-object-store/ShadowNoFileLockStore/defaultStore/EISNAME/0_ffff0a28050c_-a09a5fe_5c598d64_43, FileLock.F_WRLCK, true)
TRACE [com.arjuna.ats.arjuna] (default task-1) FileSystemStore.closeAndUnlock(data/tx-object-store/ShadowNoFileLockStore/defaultStore/EISNAME/0_ffff0a28050c_-a09a5fe_5c598d64_43, null, java.io.FileOutputStream@72d0d91)
TRACE [com.arjuna.ats.arjuna] (default task-1) StateManager::StateManager( 1, 0 )
TRACE [com.arjuna.ats.arjuna] (default task-1) AbstractRecord::AbstractRecord (0:ffff0a28050c:-a09a5fe:5c598d64:45, 1)
TRACE [com.arjuna.ats.jta] (default task-1) XAResourceRecord.XAResourceRecord ( < formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, TestXAResource(TestXAResourceCommon(id:944, xid:null, timeout:300, prepareReturn:0)) ), record id=0:ffff0a28050c:-a09a5fe:5c598d64:45
TRACE [com.arjuna.ats.arjuna] (default task-1) RecordList::insert(RecordList: empty) : appending /StateManager/AbstractRecord/XAResourceRecord for 0:ffff0a28050c:-a09a5fe:5c598d64:45

[section 3]
TRACE [com.arjuna.ats.jta] (default task-1) BaseTransaction.commit
TRACE [com.arjuna.ats.jta] (default task-1) TransactionImple.commitAndDisassociate
TRACE [com.arjuna.ats.jta] (default task-1) TransactionImple.getStatus: javax.transaction.Status.STATUS_ACTIVE
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::End() for action-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b

[section 4]
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::prepare () for action-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b
TRACE [com.arjuna.ats.jta] (default task-1) XAResourceRecord.topLevelPrepare for XAResourceRecord < resource:TestXAResource(TestXAResourceCommon(id:944, xid:< formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, timeout:300, prepareReturn:0)), txid:< formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, heuristic: TwoPhaseOutcome.FINISH_OK, product: Crash Recovery Test/EAP Test, jndiName: java:/TestXAResource com.arjuna.ats.internal.jta.resources.arjunacore.XAResourceRecord@6454bcb3 >, record id=0:ffff0a28050c:-a09a5fe:5c598d64:45
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::doPrepare() result for action-id (0:ffff0a28050c:-a09a5fe:5c598d64:3b) on record id: (0:ffff0a28050c:-a09a5fe:5c598d64:45) is (TwoPhaseOutcome.PREPARE_OK) node id: (1)
TRACE [com.arjuna.ats.arjuna] (default task-1) RecordList::insert(RecordList: empty) : appending /StateManager/AbstractRecord/XAResourceRecord for 0:ffff0a28050c:-a09a5fe:5c598d64:45
TRACE [com.arjuna.ats.arjuna] (default task-1) OutputObjectState::OutputObjectState(0:ffff0a28050c:-a09a5fe:5c598d64:3b, /StateManager/BasicAction/TwoPhaseCoordinator/AtomicAction)
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::save_state ()
TRACE [com.arjuna.ats.arjuna] (default task-1) StateManager.packHeader for object-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b birth-date 1549372780127
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::save_state - next record to pack is a 171 record /StateManager/AbstractRecord/XAResourceRecord should save it? = true

[section 5]
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::phase2Commit() for action-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::doCommit (XAResourceRecord < resource:TestXAResource(TestXAResourceCommon(id:944, xid:< formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, timeout:300, prepareReturn:0)), txid:< formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, heuristic: TwoPhaseOutcome.FINISH_OK, product: Crash Recovery Test/EAP Test, jndiName: java:/TestXAResource com.arjuna.ats.internal.jta.resources.arjunacore.XAResourceRecord@6454bcb3 >)
TRACE [com.arjuna.ats.jta] (default task-1) XAResourceRecord.topLevelCommit for XAResourceRecord < resource:TestXAResource(TestXAResourceCommon(id:944, xid:< formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, timeout:300, prepareReturn:0)), txid:< formatId=131077, gtrid_length=29, bqual_length=36, tx_uid=0:ffff0a28050c:-a09a5fe:5c598d64:3b, node_name=1, branch_uid=0:ffff0a28050c:-a09a5fe:5c598d64:44, subordinatenodename=null, eis_name=java:/TestXAResource >, heuristic: TwoPhaseOutcome.FINISH_OK, product: Crash Recovery Test/EAP Test, jndiName: java:/TestXAResource com.arjuna.ats.internal.jta.resources.arjunacore.XAResourceRecord@6454bcb3 >, record id=0:ffff0a28050c:-a09a5fe:5c598d64:45
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::doCommit() result for action-id (0:ffff0a28050c:-a09a5fe:5c598d64:3b) on record id: (0:ffff0a28050c:-a09a5fe:5c598d64:45) is (TwoPhaseOutcome.FINISH_OK) node id: (1)

[section 6]
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::updateState() for action-id 0:ffff0a28050c:-a09a5fe:5c598d64:3b
TRACE [com.arjuna.ats.arjuna] (default task-1) FileSystemStore.remove_committed(0:ffff0a28050c:-a09a5fe:5c598d64:3b, /StateManager/BasicAction/TwoPhaseCoordinator/AtomicAction)
TRACE [com.arjuna.ats.arjuna] (default task-1) ShadowingStore.remove_state(0:ffff0a28050c:-a09a5fe:5c598d64:3b, /StateManager/BasicAction/TwoPhaseCoordinator/AtomicAction, StateType.OS_ORIGINAL)
TRACE [com.arjuna.ats.arjuna] (default task-1) FileSystemStore.closeAndUnlock(data/tx-object-store/ShadowNoFileLockStore/defaultStore/StateManager/BasicAction/TwoPhaseCoordinator/AtomicAction/0_ffff0a28050c_-a09a5fe_5c598d64_3b, null, null)
TRACE [com.arjuna.ats.arjuna] (default task-1) BasicAction::End() result for action-id (0:ffff0a28050c:-a09a5fe:5c598d64:3b) is (TwoPhaseOutcome.FINISH_OK) node id: (1)
TRACE [com.arjuna.ats.jta] (default task-1) SynchronizationImple.afterCompletion - Class: class org.wildfly.transaction.client.AbstractTransaction$AssociatingSynchronization HashCode: 1685304571 toString: org.wildfly.transaction.client.AbstractTransaction$AssociatingSynchronization@6473b4fb
TRACE [com.arjuna.ats.jta] (default task-1) SynchronizationImple.afterCompletion - Class: class org.wildfly.transaction.client.provider.jboss.JBossLocalTransactionProvider$1 HashCode: 1429380276 toString: org.wildfly.transaction.client.provider.jboss.JBossLocalTransactionProvider$1@55329cb4
TRACE [com.arjuna.ats.arjuna] (default task-1) TransactionReaper::remove ( BasicAction: 0:ffff0a28050c:-a09a5fe:5c598d64:3b status: ActionStatus.COMMITTED )
```

* It's good to consider to follow with the thread id (in the log above it's `default-task-1`).
  The transaction could be suspended and started at the different thread
  but it's not usual.
* The log shows the Narayana processes the two-phase commit. Bear in mind that the example above
   shows only one resource to be part of the two-phase commit handling.
   That's intentional for the log not being too long.
* the `section-1` refers to the point where the transaction is started. The
  https://javaee.github.io/javaee-spec/javadocs/javax/transaction/Synchronization.html[JTA synchronizations]
  are registered and the transaction is added to be handled by transaction reaper
  (the transaction reaper is an independent thread taking care of transaction timeouts,
    see more at http://narayana.io/docs/project/index.html#d0e2032[section Transaction timeouts]
    in the Narayana documentation).
* At this place consider the `BasicAction` (a Narayana abstraction for the transaction)
  is identified by string `0:ffff0a28050c:-a09a5fe:5c598d64:3b`.
  It refers to the transaction id. You can track it through the log and follow
  what is happening with the particular transaction.
* the `section-2` refers to the part of business logic processing. That's the time
  when a database insertion is run or Jakarta Messaging sends a message to a queue.
  That's where you spot message containing `enlistResource`. After the resource
  is enlisted to the transaction the transaction manager saves a record
  persistently under transaction log store.
* the `section-3` refers to the time when the transaction is about to be committed.
  That means all business logic was finished (that could be the time a method
  annotated with `@Transactional` reached its end).
* the `section-4` refers to the first phase of 2PC which is _prepare_. You can see
  `XAResourceRecord.topLevelPrepare` informing what's the global transaction id
  (already defined at the start of the transaction) and the branch id
  (particular to each resource). The resource is then prepared.
* when whole prepare phase finishes Narayana saves the state into object store
* the `section-5` refers to the second phase of 2PC which is _commit_. You can see
  `XAResourceRecord.topLevelCommit` with similar information as for prepare.
* the `section-6` shows the transaction is finished, information about the transaction
  is removed from the Narayana object store and unregistered from the transaction reaper.

For more grained troubleshooting you can consider using
http://byteman.jboss.org[Byteman tool].

== Transactions configuration

Configuration related to the behaviour of the Narayana transaction manager
is covered under `transactions` subsystem. For the details refer to
link:Admin_Guide{outfilesuffix}#Transactions_Subsystem[Admin Guide Transactions subsystem].

To check the subsystem model you can use the link:wildscribe[WildFly model reference^]
or list all the configuration options of the subsystem in `jboss-cli`

[source,bash]
----
/subsystem=transactions:read-resource-description(recursive=true)
----

NOTE: References in this document to CDI refer to Jakarta Contexts and Dependency Injection unless otherwise noted.
      References in this document to Java Transaction API(JTA) refer to Jakarta Transactions unless otherwise noted.
      References in this document to Enterprise JavaBeans(EJB) refer to the Jakarta Enterprise Beans unless otherwise noted.
