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Replication Techniques

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High Level Abstraction. Group Communication. ??? ... Abstraction in Replication. Group Communication. ????? ????? ?????? ?? ?? ??? ... – PowerPoint PPT presentation

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Title: Replication Techniques


1
Replication Techniques
  • ???? ??????

2
?????
  • 1)M. Wiesmann, F. Pedone, A. Schiper B. Kemme,
    G. Alonso
  • Understanding Replication in Databases and
    Distributed Systems
  • This paper appeared in the Proceedings of
    20th International Conference on Distributed
    Computing Systems
  • (ICDCS'2000), April 2000. IEEE Computer
    Society Technical Committee on Distributed
    Processing.
  • http//citeseer.ist.psu.edu/wiesmann00understa
    nding.html
  • 2)Matthias Wiesmann Fernando Pedoney Andre
    Schiper ,Bettina Kemmez Gustavo Alonsoz
  • Database Replication Techniques a Three
    Parameter Classification 2002 Proceedings of
    19th IEEE Symposium on Reliable Distributed
    Systems

3
?????
  • 3) F. Pedone, R. Guerraoui, and A. Schiper.
  • Exploiting atomic broadcast in replicated
    databases. In Proceedings of EuroPar
  • (EuroPar98), Sept. 1998.
  • http//citeseer.ist.psu.edu/agrawal96exploiting.ht
    ml
  • 4)B. Kemme and G. Alonso.
  • A suite of database replicationprotocols based
    on group communication primitives.
  • In Proceedings of the 18th International
    Conference on Distributed Computing Systems
    (ICDCS), Amsterdam, The
  • Netherlands, May 1998.
  • http//citeseer.ist.psu.edu/kemme98suite.html

4
Replication
  • ?? ?? ???? ????? ???? ???
  • Distributed DataBase
  • Distributed System
  • Replication ?? ???????? ????? ???
  • ??? ???? ?? Replication
  • Fault tolerance
  • Failure ???? ?? ??? ????? ? application ?????
    ????

5
Group Communication
  • ?????? ?? ?? ????????? ? ???????? ??? ???? ????
    ??????? ?????? ? ???? ???????? Replicate ???
  • ???? ???? ??? Replica ?? ?????? ?? ??????? ????
    ????
  • Agreement Properties
  • Ordering Properties
  • ?????
  • Fault Tolerance
  • Consistency

6
Distributed Databases
  • Distributed Database
  • ??? performance
  • ????? ?? ????? ???? Failure ????
  • ????? crash ?????? rollback ?? ???

7
Report Objective and Approach
  • ??????
  • ?????? ???????? Replication ?? ?? ????
  • ??????? ?? ???? ??? ???? ?? Distributed Sys. ??
  • High Level Abstraction
  • Group Communication
  • ???
  • Group Communication-based replication in Data
    Base
  • ??????
  • Classification of replication Techniques
  • Distributed Database
  • Distributed System

8
Overall View
9
Distributed System
  • ??????? ?? Distributed System
  • ????? ????? ??????? ?? ????? ???
  • ???? ?????
  • Group communication
  • ??? ???? ?? Replication
  • Fault tolerance
  • Failure ???? ?? ??? ????? ? application ?????
    ????

10
Replication protocol in Distributed Sys
  • ???? 5 ??? ?? ????
  • Request
  • Server Coordination
  • Execution
  • Agreement Coordination
  • Client Response

11
Replication protocols in Distributed Sys
  • Request
  • ?? client ??????? ?? ??? ?? ?? ??? replica ??
    ?? ????? ?? ???
  • ?? ??????
  • client ?? ????? replica ?? ??????? ?? ?????
  • client ?? ?? replica??????? ??????? ??? ?????
    replica ?? ??? server coordination ?????? ?? ??
    ???? replica ?? ????? ?????
  • ???? ??????? ?? Database ??
  • ????? ???? ?? ???? ?? ??? ????? transparent ????
  • Active Replication vs. Passive Replication

12
Replication protocol in Distributed Sys
  • Server Coordination Phase
  • ?????? ?? ?? ???? ????? ????? ?????? ??????
    ?????? ???? ??????
  • Execution phase
  • ?????? ???? ?????
  • Agreement Coordination
  • replica ?? ?? ?? ????? ?? ???? ???? ?? ??? ??
    ????? ???? ???
  • Client Response Phase
  • ???? ?? ?? Client ???? ?? ?? ??? ????? ??????
    ?????

13
Replication protocol in Distributed Sys
  • Eager Replication
  • No response until everything has been done
  • Lazy Replication
  • Immediate response

14
Client A
Client A
Replica 1
Update
Replica 2
Update
Replica 3
Update
Phase 1 Request
Phase 3 Execution
Phase 4 Agreement
Phase 5 Response
Phase 2 Coordination
Client B
Client B
15
Abstraction in Replication
  • Group Communication
  • ????? ????? ?????? ?? ?? ???
  • ????? ???? ?????????? ??? ???????
  • Atomic Broadcast (ABCAST)
  • View Synchronous Broadcast (VSCAST)

16
Atomic Broadcast
  • ABCAST Provides
  • Atomicity
  • ??? ???? ?? ???? ????? m ?? ?????? ??? ???? ????
    ??? ???? ?????? ?????? ???
  • Total order
  • ??? ??? ?? ????? ???? ?? ????? m ? n ?? ?? ?????
    ???? ?? ???? ??? ?? ??? ???? ??? ??? ?? ????? ??
    ?? ???? ????? ?????? ?????

17
View Synchronous Broadcast
  • ?? ???? ????? ?????? ?? ?? view ?? ??? ?? state
    ???? ?? ???? ?? ???
  • V0,V1,V2,,Vn
  • g) ) Vi ????? ???? ???? ?? ?? ???? ???
  • ?????? ?? ??????? ?????? ?? ???? ????? ??? ?????
    ?? ?????? crash ??? View ???? Vi1 ????? ?
    Install ?? ???.
  • VSCAST ????? ????? ??? ?????? p (?? Vi ) ????? m
    ?? ??? ?? Install ???? Vi1 ?????? ??? ??????
    ????? ??? ?? ?????? m ??? ????? Vi1 ?? Install
    ????

18
Active Replication
  • client ???? ABCAST ??????? ???? Server?? ??
    ?????.
  • Server Coordination ???? ?????? Total Order?
    ABCAST ????? ?? ???.

19
Active Replication
  • ????? replica ?? ?? ?????? ?? ?? ??????? ??
    ?????? ?????? ???? ?? ???? ?????.
  • ????? replica ?? ???? ?? ?? client ?? ?? ???????
  • Same input same order gt same output
  • Clients address servers as a group
  • ?????? Input ?? ?? ????? ????? ?????? ??????

20
Passive Replication
  • ??? ?? Replica?? ?? ????? primary ??? ? ????
    backup ?????
  • client ?? ????? ?? ?? primary ?? ?????.
  • ??? initial coordination ???? ????.
  • Primary ?? ????? ?? ???? ?? ???
  • Primary ?? ???? ??????? ???????? update ?
    coordinate ?? ???.
  • Primary ???? ?? ?? client ?? ?????.

21
Replication in Database
  • ??? ?? Replication ???????? ???? ????? ???.
  • ??????
  • ???? ???? ???? ?? query
  • Replication Model ?? ?????? ???? ??
  • Client ?? ?? ???? ???????? ?? ???? ?? ??????
    ?????
  • ?? ?????? ?? ?? ?????? ???? ?? ?? conflict ?????
    ?? ?? ?? ???? ?????? ????? ????? ???? ?? ????
    write ????
  • Isolation ?? ???? ????? ?????????? concurrency
    control ??? locking protocol

22
Replicated Databases
  • One Logical Database
  • N logical replicas
  • Network connects Replicas
  • Clients connect to the logical Database.
  • Replicas processes transactions (ACID properties)

23
???????? ??? Replication
  • ??? ???? ????? Replication
  • . ????? ?? update propagation ?? ?? ???
  • eager vs. Lazy
  • ?????? ?? update ?? ????? ?? ???
  • primary vs. every where
  • eager replication
  • update ?? ?? ?? ?????? ????? ?? ???
  • ???? replica ?? ?? ??? ??????? ?? ???? ???
    ?????? commit ?????
  • ??????? ???? ?? ??? ?? ???
  • Overhead ????? ????? ???? ???
  • ???? ???? ?? ???? ???

24
???????? ??? Replication
  • Lazy Replication
  • ?? ??? ???? ?? ??? ??????? ?? ???
  • ? ?? ?? commit ?????? update ?? ??? ?? ???
  • ?????? ??????
  • ?? ???? ????? ????????? ???? ?????
  • Primary copy
  • ????? ???? primay ?? ??? ??????? ?? ??? ??? ????
    ???? ??
  • replication control ???? ??
  • Single point of failure
  • Bottleneck

25
???????? ??? Replication
  • update every where
  • ?? ??? ???? ??? ????? ?? ??? ??????? ???
  • ????? ??????? ???? ??

Update Propagation
Eager Primary Copy
Lazy Primary Copy
Update Location
Eager Update Everywhere
Lazy Update Everywhere
26
Eager primary copy replication
  • update ????? ?? primary master ????? ?? ????
  • ?? ?? ?? update ?? ???? ?????? ???? ?? ???
  • ???? primary copy ????? ??????? ???? ?? ????
    commit ?? ???

27
Eager primary copy replication
  • ??? SC ?? ??????
  • Eager Primary Copy Replication ????? Passive
    Replication
  • Eager Primary copy ? 2pc
  • Passive Replication ? VSCAST

28
Eager Update everywhere replication
  • ?? ?????? ?????? ???? ??????? ?? conflict????
    ????
  • distributed locking
  • Atomic broadcast
  • Distributed locking approach

29
Distributed locking approach
  • Client ??????? ?? ?? ??? ?? ?????? ?? ?????
  • SC ???????lock ?? ???? ?????? ??????? ?????
  • ?? ???? ?????? ????? lock ?? ??? update ?????
    ?? ?????
  • ????? 2PC

30
Data Replication based on Atomic broadcast
  • ???? ???? ??????? ?? total order ?? ??????? ??
    ABCAST
  • ???? ??????? ?????? ?? ???? ???? ??????
  • .??? SC ?? ??? 2PC ???? total order ?? ABCAST
    ????? ?? ???
  • ?? ??? ?????? ?? ????? ABCAST ?? ????? ??????
    ???? ?? ????

31
Data Replication based on Atomic broadcast
  • client ?? ????? ?? ?? server ???? ?? ?????
  • server ??????? ?? ?? ???? server ?? ?? ????
    ABCAST ?? ?????
  • server ?? ?????? ?? ???? ?? ????
  • ??? 4 ?? ???? ????? ????.
  • server ???? ?? ????? ?? ?? client ?? ?????

32
  • Eager Update everywhere
  • Active Replication

33
(No Transcript)
34
Lazy Replication
  • Overhead ????? ??
  • SC ?? ?? ???? ?? client ?? ?? ???
  • Reconciliation update ????? ?? ???? ?? ???

35
Conclusion
  • ????? ????????? ?? ?? ??????? ????? ?????
  • ??? ?? ????? ?? ?? ??? SC ? ?? AC
  • primary copy ? passive replication
  • SC ??????
  • Update Everywhere
  • SC ????

36
Another Classification for eager replication
  • ?????????? ???? ????
  • Server Architecture
  • Primary-copy
  • Update everywhere
  • Server Coordination
  • Constant Interaction
  • Linear Interaction
  • Transaction Termination
  • Voting termination
  • Non-voting termination

37
Update Everywhere Constant Interaction
Non-Voting Techniques
  • The transaction starts on the delegate server.
  • The transaction is processed in a
    non-deterministic way.
  • The point of determinism is reached.
  • The transaction is sent to all servers using an
    atomic commitment.
  • Processing continues on all replicas in a
    deterministic way.
  • Each replica terminates the transaction in the
    same way.

38
Update Everywhere Constant Interaction
Voting Techniques
  • 1. The transaction starts on the delegate server.
  • 2. The transaction is processed in a
    non-deterministic way.
  • 3. The transaction is broadcast to all servers.
  • 4. Processing continues on all replicas.
  • 5. A voting termination phase takes place.
  • 6. Each replica terminates the transaction
    according to the outcome of the voting
    protocol.

39
Recovery and Fault-ToleranceIssues
  • 1-safe when the client receives the notification
    of ts commit, t has been committed on the
    delegate or the primary server of t.
  • 2-safe when the client receives the notification
    of ts commit, t is guaranteed to eventually
    commit on all servers.
  • Group-safe when the client receives the
    notification of ts commit, t is guaranteed to
    eventually commit on group of servers.

40
Future Work
  • ???????? ???? ???? ??
  • ????? ???????? ??? Application ? ???? Group
    Communication
  • ????? ???? (Unification) ???????? ???? ??
    (Primitives) ???????? ?????
  • ????? ????? ????? ??? ????
  • ????? ??? ?????? ?? Interface ???? ???
    Application ? Group Communication
  • ??????? ?? ???????? Messaging ???? ????? ???????
  • Group-Safe Replication
  • ???? ?? ???? Fault-Tolerance
  • ?? ??? ???? ?????? ?? ???? ?? ??? ??????(Crash)
    ????
  • ??????? ?? ?? ??? ?????? f ?? ?? ?????? (0ltfltn)

41
Future Work
  • ???????? ?????? Replication
  • ?????? ?? ???????? ??? ??? ????? ???? ???? ???
  • ??????? ?? Total Order Broadcast ???? ??????? ??
    ?? ??? (Dead Lock)
  • ??????? ?? ??? Agreement Control ?? Voting ????
    ????? Atomicity
  • ?????? ???????? ??????
  • ?? ?? ??? ?????? ???????? ???? ?? ? ?? ????? (??
    Total Broadcast)
  • ??? ???? ?? Determinism
  • Replica ?? ???????? ????? ??? Deterministic ???
    ???? ? ???????? ?? Abort ???? ? Atomicity
    ????? ????? ???? ???? ?? ????? ?? ?? State ??????
    ???
  • ????? ? Specification ??????? ?????? ?????? ??
    ??? ?? ?????
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