Why jta

Chapter 1. Transactional standards provide extremely low-level interfaces for use by application programmers. Sun Microsystems has specified higher-level interfaces to assist in the development of distributed transactional applications.

If there is no active JTA transaction it lets the commit continue. I have used this when I was doing the data source program for Apple iPad Support. Home Content Places Search Cancel. Error: You don't have JavaScript enabled. This tool uses JavaScript and much of it will not work correctly without it enabled. Please turn JavaScript back on and reload this page. Please enter a title.

This terminology is usually used in the context of databases or transactional operations. The TM tells transaction participants whether to commit or roll back their data, depending on the outcome of other transaction participants. In this way, it ensures that transactions adhere to the ACID standard. A transaction participant is any resource within a transaction that has the ability to commit or to roll back state.

It is generally a database or a JMS broker, but by implementing the transaction interface, application code could also act as a transaction participant.

Each participant of a transaction independently decides whether it is able to commit or roll back its state, and only if all participants can commit does the transaction as a whole succeed.

Otherwise, each participant rolls back its state, and the transaction as a whole fails. The TM coordinates the commit or rollback operations and determines the outcome of the transaction. The TM allows applications to assign various resources, for example, database or JMS brokers, through a single global transaction. The global transaction is referred as an XA transaction.

Generally resources with XA capabilities are included in such transactions, but non-XA resources could also be part of global transactions. There are several optimizations which help non-XA resources to behave as XA capable resources. Using XTS, you can coordinate complex business transactions in a controlled and reliable manner.

The WS-Coordination WS-C specification defines a framework that allows different coordination protocols to be plugged in to coordinate work between clients, services, and participants. WS-T is developed to unify existing traditional transaction processing systems, allowing them to communicate reliably with one another. Within the scope of an AT, web services typically employ bridging to access XA resources, such as databases and message queues, under the control of the WS-T.

When the transaction terminates, the participant propagates the outcome decision of the AT to the XA resources, and the appropriate commit or rollback actions are taken by each participant.

Web Services-Business Activity WS-BA defines a protocol for web service applications to enable existing business processing and workflow systems to wrap their proprietary mechanisms and interoperate across implementations and business boundaries. Unlike the WS-AT protocol model, where participants inform the transaction coordinator of their state only when asked, a child activity within a WS-BA can specify its outcome to the coordinator directly, without waiting for a request.

A participant can choose to exit the activity or notify the coordinator of a failure at any point. This feature is useful when tasks fail because the notification can be used to modify the goals and drive processing forward, without waiting until the end of the transaction to identify failures.

The WS-BA protocols employ a compensation-based transaction model. When a participant in a business activity completes its work, it can choose to exit the activity.

This choice does not allow any subsequent rollback. Alternatively, the participant can complete its activity, signaling to the coordinator that the work it has done can be compensated if, at some later point, another participant notifies a failure to the coordinator.

In this latter case, the coordinator asks each non-exited participant to compensate for the failure, giving them the opportunity to execute whatever compensating action they consider appropriate. If all participants exit or complete without failure, the coordinator notifies each completed participant that the activity has been closed.

The transaction bridge component, txbridge , provides bi-directional linkage, such that either type of transaction can encompass business logic designed for use with the other type. The technique used by the bridge is a combination of interposition and protocol mapping.

In the transaction bridge, an interposed coordinator is registered into the existing transaction and performs the additional task of protocol mapping; that is, it appears to its parent coordinator to be a resource of its native transaction type, while appearing to its children to be a coordinator of their native transaction type, even though these transaction types differ.

The transaction bridge resides in the package org. It consists of two distinct sets of classes, one for bridging in each direction. The XA standard describes the interface between a global TM and a local resource manager. XA allows multiple resources, such as application servers, databases, caches, and message queues, to participate in the same transaction, while preserving all four ACID properties. One of the four ACID properties is atomicity, which means that if one of the participants fails to commit its changes, the other participants abort the transaction, and restore their state to the same status as before the transaction occurred.

An XA resource is a resource that can participate in an XA global transaction. An XA transaction is a transaction that can span multiple resources. It involves a coordinating TM, with one or more databases or other transactional resources, all involved in a single global XA transaction.

XA Recovery is the process of ensuring that all resources affected by a transaction are updated or rolled back, even if any of the resources that are transaction participants crash or become unavailable. XA Recovery happens without user intervention. In the event of an XA Recovery failure, errors are recorded in the log output. The XA recovery process is driven by a periodic recovery thread which is launched by default every two minutes.

The periodic recovery thread processes all unfinished transactions. It can take four to eight minutes to complete the recovery for an in-doubt transaction because it might require multiple runs of the recovery process. The transaction log might not be cleared from a successfully committed transaction.

If the JBoss EAP server crashes after an XAResource commit method successfully completes and commits the transaction, but before the coordinator can update the log, you might see the following warning message in the log when you restart the server:. This is because upon recovery, the JBoss Transaction Manager TM sees the transaction participants in the log and attempts to retry the commit.

Eventually the JBoss TM assumes the resources are committed and no longer retries the commit. In this situation, you can safely ignore this warning as the transaction is committed and there is no loss of data.

To prevent the warning, set the com. When set to true , the recovery assumes that a previous commit attempt succeeded and the instance can be removed from the log with no further recovery attempts.

This property must be used with care because it is global and when used incorrectly could result in XAResource instances remaining in an uncommitted state. JBoss EAP 7. The transaction is not rolled back and the resources remain locked until the transaction times out or a database administrator manually rolls back the resources and clears the transaction log. When the server is under excessive load, the server log might contain the following warning message, followed by a stacktrace:.

The periodic recovery process detects the transaction still in progress and attempts to initiate a rollback but in fact the transaction continues to completion. At the time the periodic recovery attempts but fails the rollback, it records the rollback failure in the server log. The underlying cause of this issue will be addressed in a future release, but in the meantime a workaround is available. Increase the interval between the two phases of the recovery process by setting the com.

A value of milliseconds is recommended. Note that this does not solve the issue. Instead it decreases the probability that it will occur and that the warning message will be shown in the log. The two-phase commit 2PC protocol refers to an algorithm to determine the outcome of a transaction.

In the first phase, the transaction participants notify the transaction coordinator whether they are able to commit the transaction or must roll back. In the second phase, the transaction coordinator makes the decision about whether the overall transaction should commit or roll back. If any one of the participants cannot commit, the transaction must roll back.

Otherwise, the transaction can commit. The coordinator directs the resources about what to do, and they notify the coordinator when they have done it.

At that point, the transaction is finished. A resource local transaction is a transaction that you have with a specific single resource using its own specific API. Such a transaction typically does not propagate to other methods in a call-stack and you are required to pass some explicit context object around.

In the majority of the resource local transactions it's not possible to have multiple resources participating in the same transaction. Here the context object is expressed by an instance of java. Other examples of resource local transactions are developers creating enterprise applications around Since transaction managers used by JTA were expensive, closed source and complicated things to setup around that era, people went with the cheaper and easier to obtain resource local variants.

You would use a JTA transaction in basically every other scenario. There's nothing to setup and they Just Work. In most cases it's advised to use those as they are easier, cleaner and less error prone. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow.