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Selective Anti-Entropy

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Summary vector: replica, full replication. Summary matrix: replica & scope, partial ... membership information of the replica set. Generic Anti-entropy Request ... – PowerPoint PPT presentation

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Title: Selective Anti-Entropy


1
Selective Anti-Entropy
  • Weibin Zhao
  • Henning Schulzrinne
  • zwb,hgs_at_cs.columbia.edu
  • Internet Real-Time Laboratory
  • Columbia University

2
Introduction
  • Anti-Entropy
  • Asynchronous replication, eventual consistency
  • Peer-wise session
  • Exchange differences, summary vector
  • Complete anti-entropy (CAE)
  • Reconcile all inconsistent states
  • Selective anti-entropy (SAE)
  • Selectively reconcile inconsistent states

3
Approach
  • Subsets of updates
  • Rx all updates initially received by Rx
  • T(Rx, Rx1, Rx2, , Rxk, Rz) SAE request
  • Only specified subsets are solicited
  • SAE types
  • Select-one-direct T(Rx, Rz, Rz)
  • Select-one-indirect T(Rx, Ry, Rz)
  • Select-multiple T(Rx, Ry, Rz, Rz)
  • Select-all CAE

4
Example SAE vs. CAE
  • R2 a,b, R3 c,d

CAE
R2 a,b,c
R3 a,c,d
d
a,b,c
R1
R1 a,b,c
R1 a,b,c,d
R2 a,b,c
R3 a,c,d
SAE
a,b
c,d
T(R1,R2,R2)
T(R1,R3,R3)
R1 a,b,c,d
R1
5
Parallel SAE Sessions
  • All select-one-direct sessions
  • In general, Rx can run k SAE sessions s1,
    s2, , sk in parallel if update subsets u1,
    u2, , uk do not overlap,
    i.e., u1 ? u2 ? ? uk ?
  • Example
  • if u1 R2, R4, u2 R3, R5,
    then R1 can run s1 and s2 in parallel

6
Multi-Scope Partial Replication
  • State set divided into subsets scopes
  • Applications directory services
  • SLP directories scopes
  • UDDI registries classifications

R1(S1,S2,S3)
R2(S1)
R3(S1,S2)
R4(S2,S3)
R5(S3)
R6(S1,S2)
R7(S3)
7
Summary Problem
(2)
State Scope ID
a S1 (R6, t1)
b S2 (R6, t2)
c S1 (R6, t3)
  • Solution space
  • Summary vector replica, full replication
  • Summary matrix replica scope, partial
    replication
  • SAE summary vector replica, partial replication

R2(S1)
R3(S1,S2)
a,c
a,c
(3)
b?
(1)
R6(S1,S2)
R6 states (t1ltt2ltt3)
8
Safe SAE Sessions
  • select-one-direct T(Rx, Rz, Rz)
  • Safe for all
  • select-one-indirect T(Rx, Ry, Rz)
  • Safe if S(Rx) ? S(Ry) ? S(Rz)
  • Safe T(R3, R1, R6)
  • S(R3) ? S(R1) S1, S2 S(R6)
  • Unsafe T(R3, R6, R2)
  • S(R3) ? S(R6) S1, S2 ? S(R2) S1
  • select-multiple or select-all
  • Safe if all select-one-indirect sessions are safe

R1(S1,S2,S3)
R2(S1)
R3(S1,S2)
R6(S1,S2)
9
Conclusions
  • Advantages of SAE
  • Generalize CAE select-all CAE
  • Fine control of received subsets of updates
  • Perform multiple SAE sessions in parallel
  • Support multi-scope partial replication
    efficiently
  • Prerequisite of SAE
  • membership information of the replica set
  • Generic Anti-entropy Request
  • Anti-entropy type selective or complete
  • Each entry lower upper bound timestamps
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