Transactional OSGi Applications Done Right

Transactional OSGi applications done right
& Karl Pauls
Clement Escoffier , akquinet

Outline
Transactions ???
OSGi Transaction Service (RFC-98)
Transaction & Dynamism …
From “Hell” to the “EJB3-paradise”
2

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

Transactions ???
Properties
(Failure) Atomicity : the action is performed either entirely or not at all
Consistency : from a consistent state to another consistent state
Isolation: 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.
4

Transactions ??
Transaction Engine
commit
begin
Sequence of actions
rollback
5
Uses
Resources

Why an OSGi Transaction Service ?
A lot of OSGi applications deals with
Devices
Database
Remote resources and services
=> Need transactions to ensure the system consistency
6

OSGi Transaction Service
Based on Java Transaction API
XA resources
Transaction-aware “critical” resources
JTA common interfaces are provided as OSGi services
User Transaction: programmatic transactions
Transaction Synchronization Registry: used by server components such as persistence managers to register synchronization object
Transaction Manager: allows the server to control transaction boundaries on behalf of the application being managed.
7

OSGi Transaction Service
ServiceReferencetxRef = 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.
}
8

Great … but
9

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 !
10

The “EJB dream”
Avoid the developer to manage transactions manually
Transaction demarcation:method
Transactional method declares the transaction propagation
REQUIRED, REQUIRES_NEW, SUPPORTS, NOT_SUPPORTED, MANDATORY, NEVER
The transaction management is made by the container
@TransactionAttribute(REQUIRES_NEW)
public void firstMethod() {...}
@TransactionAttribute(REQUIRED)
public void secondMethod() {...}
11

iPOJO Transaction Supports
iPOJO Transaction handler
Automates transaction management
Allows using transaction just like with EJB
@Transaction
public class MyClass {
@Requires
public FooServicefoo;
@Transactionnal(propagation="requiresnew")
public void firstMethod () {
// ...
foo.foo(); // Invoke a service
//...
}
@Transactionnal (propagation=“required”)
public void secondMethod() {...}
// …
}
12

iPOJO Transaction and dynamism
How to automate transaction management ?
The transaction management is made by the container
Flexible
Allows injecting the current Transaction inside a field
Can notify the POJO of the current transaction progress
What 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 invalid
How to support dynamism inside XA resources and volatile resources ?
The Transactional Service Providing handler emulates XA Resources or Volatile resources
Experimental…
13

Conclusion
Transactions are becoming more and more important inside OSGi applications
The Transaction Service is definitely Welcome
THANKS !
However, we’ve to take care to avoid the Transaction Nightmare
iPOJO proposes EJB-like transaction management reducing the pain !
14

Questions ?
15
Karl Paulskarl.pauls@akquinet.de
Bülowstraße 66, 10783 Berlin+49 151 226 49 845
Dr. Clement Escoffierclement.escoffier@akquinet.de
Bülowstraße 66, 10783 Berlin+49 175 246 77 17

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Transactional OSGi Applications Done Right

by clement.escoffier on Jun 23, 2009

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Transactional OSGi Applications Done Right — Presentation Transcript