another approach to instance migration

Another Approach to Service Instance Migration

Nannette Liske, Christian Stahl, Niels Lohmann, Karsten Wolf

Humboldt Univ. Techn. Univ. University ofBerlin Eindhoven Rostock

Service

Service

Liske, Lohmann, Stahl, Wolf: Another Approach to Service Instance Migration 2


•We consider business services•many internal states•complex interaction•long running

•We consider service models•states•labeled transitions

•send: !x•receive: ?y•internal: τ

•correct = •deadlock free•bounded channels

?c!a

?b•We can translate

BPEL2oWFN

UML2oWFN

oWFN2BPEL



Why?Long running services may need to be modified ... even running instances

•new legal requirements•new technology•mergers and acquisitions

What?•Freeze old service in some state (preferrably current)•setup new service in fitting state•continue with new service, interacting with the partner(s) of the old one

ChallengeInteracting partners should be able to seamlessly continue interaction



On formal model:

?c!a

?b?c

?c

!a

?b

τ

τ

τ

Problem statement:Given two services Sold and Snew, compute large set of jumper transitions

where

every correctly interacting partner of Sold is a correctly interacting partner of Sold ⊕ Snew ⊕ J

„Hybrid model“


Another Approach to Service Instance Migration[Ryu, Casati et al]•compute jumper transitions based on backward (history) and forward (future) traceinclusion•synchronous communication•implicitly assume deterministic models•unique names for the activities

[Rinderle-Ma, Reichert, Dadam]•migrate workflows•consider sequence of elementary modifications (insert/delete activity, change order)•consider data

[van der Aalst, Basten]•compare two workflows using projection inheritance (stricter than our notion)

Our Approach•compute jumper transitions based on reasoning about correctly interacting partners•asynchronous communication•nondeterministic models


Service ???

?€

?C ?T

!B !B

!€

!C?B

!€

!T?B

!T

!€?B

!C

!€?B

!€!C

?B

!T?B

....!€

!€ !€!T

!T !C

!C

?B ?B


1. Correctly interacting partners


Service ???

?€

?C ?T

!B !B

!€

!C?B

!€

!T?B

!T

!€?B

!C

!€?B

!€!C

?B

!T?B

....!€

!€ !€!T

!T !C

!C

?B ?B

mostpermissive




Service ???!€!€ !€

!T

!T !C

!C

?B ?B

!€!C

?B

!T?B



!€!€ !€

!T

!T !C

!C

?B ?B

!€!T?B

mostpermissive



2. Characterize J

qold ? qnew

Consider Snew ⊕ MPP(Sold)

States....,[qnew,q‘1,M‘1],[qnew,q‘2,M‘2],[qnew,q‘3,M‘3],...,[qnew,q‘n,M‘n],...

⊆

Idea: In the frozen state qold, partner and pending messages are in a situation thatthey could have been in with qnew, had they started with Snew from the beginning.

Consider Sold ⊕ MPP(Sold)

States....,[qold,q1,M1],[qold,q2,M2],[qold,q3,M3],...,[qold,qm,Mm],...

Formally:



Example 1

?c!a

?b?c

?c

!a

?b

SoldSnew

A

B C

D

MPP(Sold)

?a

?a

!b

!b

⊕?c

!a

?b

[A,a] [B,ab][C,-] [D,b]

[B,a] [D,-]

[A,-] [B,b]

⊕

?c?c

!a

?b

[A,a] [B,ab][C,-] [D,b]

[B,a] [D,-] ∅

[A,-] [B,b]



Example 2

?d

?e

Sold Snew

?f

!g

?d

?e ?f

!g

?d

Example 3

?h

!i

Sold Snew

!j

?h

!i !j

?h



Maximality

Computed set of jumper transitions is max if

•services are subsititutable (initial state can be migrated into each other)•want to migrate only into states of Snew reachable with some partner of Sold



Numbers

Service Sold | Interface | States of Sold States of MPP(Sold)

States of Snew

Travel service 10 34 192 202

Purchase Order 10 402 168 176

Ticket Reservation

9 304 110 118

Internal Order 7 1,516 96 104

Contract Negotiation

11 784 576 588

Deliver Finished Goods

14 182 1,632 1,394

Passport Application

11 14,569 1,536 1,540



Numbers

Service Sold States Snew⊕MPP(Sold)

Theoretical Search space

| J | time (sec)

Travel service 2,976 3,333,120 49 2.1

Purchase Order 1,031 4,886,940 359 0.6

Ticket Reservation

2,545 19,851,000 429 1.3

Internal Order 1,455 34,460,220 1,613 0.9

Contract Negotiation

17,331 856,844,640 866 12.9

Deliver Finished Goods

60,753 1,050,783,888 197 123.1

Passport Application

100,975 990,199,624,400 22,382 518.1

Tool and examples: http://www.service-technology.org/live/migration/



Tools related to this presentation

available at www.service-technology.org/tools

•mia compute the jumper transitions

•bpel2owfn translate BPEL to Petri nets•uml2owfn translate UML activity diagrams to Petri nets•owfn2bpel translate Petri nets to abstract BPEL

•wendy synthesize a (most permissive) partner

•sayo compute a public view

and several more



Conclusion

•approach feasible•implemented•different from existing approaches•can be combined (just intersect the resulting jumper sets)

Next steps

•take care of data dependencies and life cycles•concurrent migration


Nannette Liske, Christian Stahl, Niels Lohmann, Karsten Wolf

Humboldt Univ. Techn. Univ. University ofBerlin Eindhoven Rostock

Service

Service

another approach to instance migration

Technology

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service models

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