Providing Fault-Tolerant Group Membership into JuxMem

1. Providing Fault-Tolerant Group Membership into JuxMem Sébastien Monnet GDS Meeting May 4th, Rennes

2. Motivations

3. Fault tolerance • Data replication • Active • Passive • Quorum • More than one copy up-to-date • Guaranties are needed • Multiple updates • Consistency GDS meeting, Rennes

4. Active data replication GDS meeting, Rennes

5. Active data replication GDS meeting, Rennes

6. Goals • Mechanism that ensures messages are delivered • By every peers in a group • In the same order • Atomic multicast • Keep the replication degree even in case of failure • Fault-tolerant group membership GDS meeting, Rennes

7. Goals: atomic multicast Group GDS meeting, Rennes

8. Goals: conserve replication degree Group • Failure detection • Support for join& leave GDS meeting, Rennes

9. What’s new ? • Relies on the existing architecture • New design (more modular) • Plug different • Failure detectors • Replication strategies • Mainly: Reliable atomic multicast • All members deliver the same set of messages • Messages are delivered in the same order GDS meeting, Rennes

10. Fault-tolerant group membership (FTGM) • Associated with an ID • Messages delivered in the same order to all members • Peers can join or leave the FTGM • Faulty peers detection and replacement Fault-tolerant group membership GDS meeting, Rennes

11. Adapter Failure detector FTGM needs Fault-tolerant group membership Group membership GDS meeting, Rennes

12. Adapter Failure detector Failure detector (FD) • Configurable QoS • Suspected peers list GDS meeting, Rennes

13. Adapter Failure detector FTGM needs Fault-tolerant group membership Group membership GDS meeting, Rennes

14. Group membership (GM) Group membership • Associated with an ID • Messages delivered in the same order to all members • Peers can join or leave the GM • Implementation • Stores a member list • Ordered message queue GDS meeting, Rennes

15. Group membership needs Group membership Atomic multicast Communications GDS meeting, Rennes

16. Atomic multicast (AMCAST) • API: send(Message m) • Number message • Multicast it • May be partitioned in • Atomic multicast • Multicast Atomic multicast GDS meeting, Rennes

17. Atomic multicast needs Atomic multicast Consensus Communications GDS meeting, Rennes

18. Consensus Consensus • API: Object decide(Object proposition) • Real consensus • Efficiency • 3 peers needed at least • Replicated serialization peer • Less powerful • Enough GDS meeting, Rennes

19. Adapter Failure detector Consensus needs Consensus Communications GDS meeting, Rennes

20. Send(ID, message) Recv(ID, message) Communications • Unreliable • Reliable Communications GDS meeting, Rennes

21. The big picture Communications Fault-tolerant group membership Adapter Group membership Atomic multicast Consensus Adapter Failure detector GDS meeting, Rennes

22. members num Sample : atomic multicast FTGM Adap GM AMCAST Consensus Adap FD GDS meeting, Rennes

23. Sample: atomic multicast (continued) Group GDS meeting, Rennes

24. Current state: Non fault-tolerant • Network • JXTA Pipes considered as reliable • Peers • No failure detection • 1 peer numbers all group messages • 1 peer receives and atomic multicast in the group all external messages GDS meeting, Rennes