1. AOP: Does It Make Sense? The Case of Concurrency and Failures by Jörg Kienzle and Rachid Guerraoui Sibylle Aregger & Antonia Schmidig Presentation based on

2. Concurrency SeminarSS 20042 NO!

3. Concurrency SeminarSS 20043 The Problem aspectizing Concurrency and Failures AspectJ & Transactions aspectize transaction semantics aspectize transaction interfaces aspectize transaction mechanisms

4. Concurrency SeminarSS 20044 Overview 1.Transactions 2.AOP (Aspect Oriented Programming) 3.aspectize transaction semantics 4.aspectize transaction interfaces 5.aspectize transaction mechanisms 6.Conclusion

5. Concurrency SeminarSS 20045 Transactions ACID Serializability Concurrency Failure Recovery => fundamental paradigm to handle Concurrency and Failures

6. Concurrency SeminarSS 20046 AOP separation of concerns -> separate code (aspect) Weaving Code + Aspect(s) = Program

7. Concurrency SeminarSS 20047 AOP: Example [Picture: Figure/Point/Line Example]

8. Concurrency SeminarSS 20048 AOP: JoinPoint JoinPoint: –point in flow of program –„hook“ to insert aspect-code Method JoinPoint Program Flow

9. Concurrency SeminarSS 20049 AOP: PointCut PointCut: –set of JoinPoints pointcut moves(): receptions(void Line.setP1(Point)) || receptions(void Line.setP2(Point)) || receptions(void Point.setX(int)) || receptions(void Point.setY(int));

10. Concurrency SeminarSS 200410 AOP: Advice Before After Around Method JoinPoint Program Flow

11. Concurrency SeminarSS 200411 AOP: Example aspect MoveTracking { static boolean flag = false; static boolean testAndClear() { boolean result = flag; flag = false; return result; } pointcut moves() :... after() : moves() { flag = true; } }

12. Concurrency SeminarSS 200412 Aspectize Transaction Semantics combine non-transactional code with transaction aspects problems: –irreversible actions –deadlock

13. Concurrency SeminarSS 200413 ATS: Unsolvable Deadlock T1: A.deposit(Amount) while (B.getBalance() <= Amount) {} B.withdraw(Amount) T2: B.deposit(Amount) while (A.getBalance() <= Amount) {} A.withdraw(Amount) Problem: linearizability  serializability Solution: multithreaded transactions New Problem: automatic detection of cooperating threads

14. Concurrency SeminarSS 200414 Aspectize Transaction Interfaces

15. Concurrency SeminarSS 200415 Aspectize Transaction Mechanisms

16. Concurrency SeminarSS 200416 Conclusion aspectize transaction semantics: not possible aspectize transaction interfaces: possible, but artificial aspectize transaction mechanisms: only syntactical separation