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Chapter 14. Configuring Transactions

14.1. Transactions Subsystem Configuration

14.1.1. Configuring the Transaction Manager

You can configure the transaction manager using the web-based management console or the command line management CLI.

Configuring the Transaction Manager Using the Management Console

The following steps explain how to configure the transaction manager using the web-based management console:

Select the Configuration tab from the top of the screen.
If you are running JBoss EAP as a managed domain, choose the desired profile to modify.
From the Subsystem list, select Transactions and click View.
Click Edit on the appropriate tab for the settings that you want to edit, such as Recovery for recovery options.
Make the necessary changes and click Save to save the changes.
Click Need Help? to display help text.

Configuring the Transaction Manager Using the Management CLI

Using the management CLI, you can configure the transaction manager using a series of commands. The commands all begin with /subsystem=transactions for a standalone server or /profile=default/subsystem=transactions/ for the default profile in a managed domain.

For a detailed listing of all the transaction manager configuration options, see the Transaction Manager Configuration Options for JBoss EAP.

14.1.2. Configuring Your Datasource to Use JTA

This task shows you how to enable Java Transaction API (JTA) on your datasource.

Prerequisites

Your database must support Java Transaction API. If in doubt, consult the documentation for your database.
Create a non-XA datasource.
Note
XA datasources are already JTA capable by default.

Configuring the Datasource to use Java Transaction API

Use the following management CLI command to set the jta attribute to true.
```
/subsystem=datasources/data-source=DATASOURCE_NAME:write-attribute(name=jta,value=true)
```
Note
In a managed domain, precede this command with /profile=PROFILE_NAME.
Reload the server for the changes to take effect.
```
reload
```

Your datasource is now configured to use JTA.

14.1.3. About Transaction Log Messages

You can track the transaction status while keeping the log files readable by using the DEBUG log level for the transaction logger. For detailed debugging, use the TRACE log level. Refer to Configuring Logging for the Transactions Subsystem for information on configuring the transaction logger.

Transaction Manager (TM) can generate a lot of logging information when configured to log in the TRACE log level. Following are some of the most commonly-seen messages. This list is not comprehensive, so you may see messages other than these.

Table 14.1. Transaction State Change
Transaction Begin	When a transaction begins, a method `Begin` of class `com.arjuna.ats.arjuna.coordinator.BasicAction` is executed and presented in the log with the message `BasicAction::Begin() for action-id <transaction uid>`.
Transaction Commit	When a transaction commits, a method `Commit` of class `com.arjuna.ats.arjuna.coordinator.BasicAction` is executed and presented in the log with the message `BasicAction::Commit() for action-id <transaction uid>`.
Transaction Rollback	When a transaction rolls back, a method `Rollback` of class `com.arjuna.ats.arjuna.coordinator.BasicAction` is executed and presented in the log with the message `BasicAction::Rollback() for action-id <transaction uid>`.
Transaction Timeout	When a transaction times out, a method `doCancellations` of `com.arjuna.ats.arjuna.coordinator.TransactionReaper` is executed and presented in log as `Reaper Worker <thread id> attempting to cancel <transaction uid>`. You will then see the same thread rolling back the transaction as shown above.

14.1.4. Configuring Logging for the Transactions Subsystem

You can control the amount of information logged about transactions, independent of other logging settings in JBoss EAP. You can configure the logging settings using the management console or the management CLI.

Configuring the Transaction Logger Using the Management Console

Navigate to the Logging subsystem configuration.
1. In the management console, click the Configuration tab. If you use a managed domain, you must first choose the appropriate server profile.
2. Select the Logging subsystem and click View.
Edit the com.arjuna attributes.
Select the Log Categories tab. The com.arjuna entry is already present. Select com.arjuna and click Edit in the Attributes section. You can change the log level and choose whether to use parent handlers or not.
- Log Level:
  As transactions can produce a lot of logging output, the default logging level is set to WARN so that the server log is not overwhelmed by transaction output. If you need to check transaction processing details, use the TRACE log level so that transaction IDs are shown.
- Use Parent Handlers:
  Parent handler indicates whether the logger should send its output to its parent logger. The default behavior is true.
Click Save to save the changes.

Configuring the Transaction Logger Using the Management CLI

Use the following command to set the logging level from the management CLI. For a standalone server, remove the /profile=default from the command.

/profile=default/subsystem=logging/logger=com.arjuna:write-attribute(name=level,value=VALUE)

14.2. Transaction Administration

14.2.1. Browse and Manage Transactions

The management CLI supports the ability to browse and manipulate transaction records. This functionality is provided by the interaction between the TM and the management API of JBoss EAP.

The TM stores information about each pending transaction and the participants involved the transaction, in a persistent storage called the object store. The management API exposes the object store as a resource called the log-store. The probe operation reads the transaction logs and creates a node path for each record. You can call the probe operation manually, whenever you need to refresh the log-store. It is normal for transaction logs to appear and disappear quickly.

Refresh the Log Store

The following command refreshes the log store for server groups which use the profile default in a managed domain. For a standalone server, remove the profile=default from the command.

/profile=default/subsystem=transactions/log-store=log-store:probe

View All Prepared Transactions

To view all prepared transactions, first refresh the log store (see Refresh the Log Store), then run the following command, which functions similarly to a file system ls command.

ls /profile=default/subsystem=transactions/log-store=log-store/transactions

/host=master/server=server-one/subsystem=transactions/log-store=log-store:read-children-names(child-type=transactions)

Each transaction is shown, along with its unique identifier. Individual operations can be run against an individual transaction (see Manage a Transaction).

14.2.1.1. Manage a Transaction

View the Attributes of a Transaction

To view information about a transaction, such as its JNDI name, EIS product name and version, or its status, use the read-resource operation.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9:read-resource

View the Details of a Transaction Participant

Each transaction log contains a child element called participants. Use the read-resource operation on this element to see the details of a participant of the transaction. Participants are identified by their JNDI names.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9/participants=java\:\/JmsXA:read-resource

The result may look similar to this:

{
   "outcome" => "success",
   "result" => {
       "eis-product-name" => "ActiveMQ",
       "eis-product-version" => "2.0",
       "jndi-name" => "java:/JmsXA",
       "status" => "HEURISTIC",
       "type" => "/StateManager/AbstractRecord/XAResourceRecord"
   }
}

The outcome status shown here is in a HEURISTIC state and is eligible for recovery. See Recover a Transaction Participant for more details.

In special cases it is possible to create orphan records in the object store, that is XAResourceRecords, which do not have any corresponding transaction record in the log. For example, XA resource prepared but crashed before the TM recorded and is inaccessible for the domain management API. To access such records you need to set management option expose-all-logs to true. This option is not saved in management model and is restored to false when the server is restarted.

/profile=default/subsystem=transactions/log-store=log-store:write-attribute(name=expose-all-logs, value=true)

You can use this alternate command, which shows participant IDs of transaction in an aggregated form.

/host=master/server=server-one/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9:read-children-names(child-type=participants)

Delete a Transaction

Each transaction log supports a delete operation, to delete the transaction log representing the transaction.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9:delete

This deletes all participants in the transaction as well.

Recover a Transaction Participant

Each transaction participant supports recovery by using the recover operation.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9/participants=2:recover

If the transaction participant’s status is HEURISTIC, the recover operation switches the status to PREPARE and asks the periodic recovery process to replay the commit.

If the commit is successful, the participant is removed from the transaction log. You can verify this by running the probe operation on the log-store and checking that the participant is no longer listed. If this is the last participant, the transaction is also deleted.

Refresh the Status of a Transaction Participant

If a transaction needs recovery, you can use the refresh operation to be sure it still requires recovery, before attempting the recovery.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9/participants=2:refresh

14.2.2. View Transaction Statistics

If transaction manager statistics are enabled, you can view statistics on processed transactions by the transaction manager. See Configuring the Transaction Manager for information about how to enable transaction manager statistics.

You can view statistics using either the management console or the management CLI. In the management console, transaction statistics are available by navigating to the Transactions subsystem from the Runtime tab. From the management CLI, you can view statistics by using include-runtime=true to the read-resource operation. For example:

/subsystem=transactions:read-resource(include-runtime=true)

The following table shows each available statistic and its description.

Table 14.2. Transactions Subsystem Statistics
Statistic	Description
number-of-transactions	The total number of transactions processed by the transaction manager on this server.
number-of-committed-transactions	The number of committed transactions processed by the transaction manager on this server.
number-of-aborted-transactions	The number of aborted transactions processed by the transaction manager on this server.
number-of-timed-out-transactions	The number of timed out transactions processed by the transaction manager on this server. The number of timed out transactions is calculated to number of aborted transactions too.
number-of-heuristics	Number of transactions in a heuristic state.
number-of-inflight-transactions	Number of transactions which have begun but not yet terminated.
number-of-application-rollbacks	The number of failed transactions whose failure origin was an application.
number-of-resource-rollbacks	The number of failed transactions whose failure origin was a resource.

14.2.3. Transactions Object Store

Transactions need a place to store objects. One of the options for object storage is a JDBC datasource. If performance is a particular concern, the JDBC object store can be slower than a file system or ActiveMQ journal object store.

Important

If the transactions subsystem is configured to use Apache ActiveMQ Artemis journal as storage type for transaction logs, then two instances of JBoss EAP are not permitted to use the same directory for storing the journal. Application server instances can not share the same location and each has to configure a unique location for it.

Note

Losing a transaction object store can lead to losing data consistency. Thus, the object store needs to be placed on a safe drive.

Use a JDBC Datasource as a Transactions Object Store

Follow the below steps to use a JDBC datasource as a transactions object store.

Create a datasource, for example, TransDS. For instructions, see Create a Non-XA datasource. Note that the datasource’s JDBC driver must be installed as a core module, not as a JAR deployment, for the object store to work properly.

Set the datasource’s jta attribute to false.

/subsystem=datasources/data-source=TransDS:write-attribute(name=jta, value=false)

Set the jdbc-store-datasource attribute to the JNDI name for the datasource to use, for example, java:jboss/datasources/TransDS.
```
/subsystem=transactions:write-attribute(name=jdbc-store-datasource, value=java:jboss/datasources/TransDS)
```

Set the use-jdbc-store attribute to true.

/subsystem=transactions:write-attribute(name=use-jdbc-store, value=true)

Restart the JBoss EAP server for the changes to take effect.

Transactions JDBC Store Attributes

The following table identifies all of the available attributes related to JDBC object storage.

Table 14.3. Transactions JDBC Store Attributes
Property	Description
use-jdbc-store	Set this to `true` to enable the JDBC store for transactions.
jdbc-store-datasource	The JNDI name of the JDBC datasource used for storage.
jdbc-action-store-drop-table	Whether to drop and recreate the action store tables at launch. The default is `false`.
jdbc-action-store-table-prefix	The prefix for the action store table names.
jdbc-communication-store-drop-table	Whether to drop and recreate the communication store tables at launch. The default is `false`.
jdbc-communication-store-table-prefix	The prefix for the communication store table names.
jdbc-state-store-drop-table	Whether to drop and recreate the state store tables at launch. The default is `false`.
jdbc-state-store-table-prefix	The prefix for the state store table names.

Use the ActiveMQ Journal Object Store

Follow the below steps to use an ActiveMQ journal object store.

Set the use-journal-store attribute to true.

/subsystem=transactions:write-attribute(name=use-journal-store,value=true)

Restart the JBoss EAP server for the changes to take effect.