Transactional OSGi applications done right & Karl PaulsClement Escoffier , akquinet

OutlineTransactions ???OSGi Transaction Service (RFC-98)Transaction & Dynamism …From “Hell” to the “EJB3-paradise”2Transactional OSGi applications done right

Transactions ???Transactions are a mechanism that allows endowing a sequence of actions with the properties of a single atomic (indivisible) action.3Transactional OSGi applications done right

Transactions ???Properties(Failure) Atomicity : the action is performed either entirely or not at allConsistency : from a consistent state to another consistent stateIsolation: no intermediate states are visible to any concurrently executing action.Durability: after a transaction has committed, the changes that it made are immune to failures (catastrophes excluded).Transactions are a mechanism that allows endowing a sequence of actions with the properties of a single atomic (indivisible) action.4Transactional OSGi applications done right

Transactions ??Transaction EnginecommitbeginSequence of actionsrollback5Transactional OSGi applications done rightUsesResources

Why an OSGi Transaction Service ?A lot of OSGi applications deals withDevicesDatabaseRemote resources and services=> Need transactions to ensure the system consistency6Transactional OSGi applications done right

OSGi Transaction ServiceBased on Java Transaction APIXA resourcesTransaction-aware “critical” resourcesJTA common interfaces are provided as OSGi servicesUser Transaction: programmatic transactionsTransaction Synchronization Registry: used by server components such as persistence managers to register synchronization objectTransaction Manager: allows the server to control transaction boundaries on behalf of the application being managed. 7Transactional OSGi applications done right

OSGi Transaction ServiceServiceReferencetxRef = bundleContext.getServiceReference("javax.transaction.UserTransaction"); UserTransactiontx = (UserTransaction)bundleContext.getService(txRef); // begin transaction tx.begin(); // perform some operations in the context of the transaction try { // Create a transactional resource ConfigResourceconfig = ...; // Perform some transactional work Configuration x = config.createConfiguration("abc"); tx.commit(); // make changes persistent } catch (Throwableth) { tx.rollback(); // rollback changes. } 8Transactional OSGi applications done right

Great … but9Transactional OSGi applications done right

Dynamism impact …How to automate transaction management ?What happens when a transaction “thread” accesses a service leaving before the end of the transaction ?How to support dynamism with XA resources and volatile resources ?The OSGi Transaction service provides everything to go further ! 10Transactional OSGi applications done right

The “EJB dream”Avoid the developer to manage transactions manuallyTransaction demarcation:methodTransactional method declares the transaction propagationREQUIRED, REQUIRES_NEW, SUPPORTS, NOT_SUPPORTED, MANDATORY, NEVERThe transaction management is made by the container@TransactionAttribute(REQUIRES_NEW) public void firstMethod() {...} @TransactionAttribute(REQUIRED) public void secondMethod() {...}11Transactional OSGi applications done right

iPOJO Transaction SupportsiPOJO Transaction handlerAutomates transaction managementAllows using transaction just like with EJB@Transactionpublic class MyClass { @Requires public FooServicefoo; @Transactionnal(propagation="requiresnew") public void firstMethod () {// ...foo.foo(); // Invoke a service//... } @Transactionnal (propagation=“required”) public void secondMethod() {...} // … }12Transactional OSGi applications done right

iPOJO Transaction and dynamismHow to automate transaction management ?The transaction management is made by the containerFlexible Allows injecting the current Transaction inside a fieldCan notify the POJO of the current transaction progressWhat happens when a transaction “thread” accesses a service leaving before the end of the transaction ?The transaction is roll backed as soon as an instance becomes invalidHow to support dynamism inside XA resources and volatile resources ? The Transactional Service Providing handler emulates XA Resources or Volatile resourcesExperimental…13Transactional OSGi applications done right

ConclusionTransactions are becoming more and more important inside OSGi applicationsThe Transaction Service is definitely WelcomeTHANKS !However, we’ve to take care to avoid the Transaction NightmareiPOJO proposes EJB-like transaction management reducing the pain !14Transactional OSGi applications done right

Questions ?Transactional OSGi applications done right15Karl Paulskarl.pauls@akquinet.deBülowstraße 66, 10783 Berlin+49 151 226 49 845Dr. Clement Escoffierclement.escoffier@akquinet.deBülowstraße 66, 10783 Berlin+49 175 246 77 17