Atomic Transactions

8/10/2019 Atomic Transactions

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Atomic TransactionsCS-4513, D-Term 2007 1

Atomic Transactions in

Distributed Systems

CS-4513

D-Term 2007(Slides include materials rom Operating System Concepts, 7t!ed", by Silbers!at#, $al%in, & $a'ne,

Modern Operating Systems, 2nded", by Tanenbaum, andDistributed Systems: Principles & Paradigms, 2nded" y Tanenbaum and )an Steen*


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Deinition + Transaction

A seuence o o.erations t!at .erorm a

sin'le lo'ical unction /am.les

it!drain' money rom your account

ain' an airline reser%ation

ain' a credit-card .urc!ase

...

sually used in contet o databases


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Deinition +Atomic Transaction

A transaction t!at !a..ens com.letely or

not at all 6o .artial results

/am.le Cas! mac!ine !ands you cas! and deducts amount

rom your account

Airline conirms your reser%ation and+ 8educes number o ree seats

+ C!ar'es your credit card

+ (Sometimes* increases number o meals loaded on li'!t


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Atomic Transaction 8e%ie

9undamental .rinci.les +A C I D

+Atomicity+ to outside orld, transaction!a..ens indi%isibly

+Consistency+ transaction .reser%es system

in%ariants

+Isolated+ transactions do not interere it!

eac! ot!er

+Durable+ once a transaction commits,t!e

c!an'es are .ermanent


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Distributed Atomic Transactions

Atomic transactions t!at s.an multi.le sites

and:or systems Same semantics as atomic transactions on

sin'le systemA C I D

9ailure modes Cras! or ot!er ailure o one site or system

6etor ailure or .artition

y#antine ailures


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Atomic TransactionsCS-4513, D-Term 2007 ;

To-

=ne site is elected coordinatoro t!e

transaction T SeeElectional'orit!ms (..t, !tml*

Phase : !en coordinator is ready to

commit t!e transaction


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To-

Phase $:Coordinator

+> any .artici.ant re.liesAbort(T*


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Atomic TransactionsCS-4513, D-Term 2007 @

To-


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Atomic TransactionsCS-4513, D-Term 2007

To-

coordinator .artici.ant

PREPARE


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9ailure 8eco%ery + To-

9ailure modes (rom coordinators .oint o %ie*

+=n cras!

+'aitstate 6o res.onse rom some .artici.ant

to !ote"re#uestmessa'e

9ailure modes (rom .artici.ants .oint o %ie*

+=n cras!+eadystate 6o messa'e rom coordinator to

%lobal"Abort(T* or %lobal"Commit(T*


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?ac o 8es.onse to Coordinator

!ote"e#uest(T* messa'e

/"'",

+.artici.ant cras!

+6etor ailure

Timeout is considered eui%alent toAbort

+


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Coordinator Cras!

>ns.ect ?o'

>Abortor Commitstate+ 8esend corres.ondin' messa'e

+ Tae corres.ondin' local action

>Preparestate, eit!er+ 8esend !ote"re#uest(T* to all ot!er .artici.ants and

ait or t!eir res.onsesB or

+ nilaterally abort transaction >"e", .utAbort(T* in on lo' on stable store

Send %lobal"Abort(T* messa'e to all .artici.ants

> not!in' in lo', abort transaction as abo%e


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6o 8es.onse to


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ns.ect local lo'

+Commitstate 8edo:re.lay t!e transaction

+Abortstate

ndo:abort t!e transaction

+6o records about T

Same as local"abort(T*

+eadyState

Same as no res.onse toeady"to"commit(T* messa'e


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To-

idely used in distributed transaction and

database systems $enerally ors ell

+!en coordinators are liely to reboot uicly

+!en netor .artition is liely to end uicly

Still subect to .artici.ant blocin'


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Atomic TransactionsCS-4513, D-Term 2007 1;

T!ree-

inor %ariation

idely uoted in literature

8arely im.lemented ecause indeinite blocin' due to coordinator

ailures doesnt !a..en %ery oten in real lie


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PREPARE

T!ree-

T!ere is no state rom !ic! a transition can bemade to eit!er Commitor Abort

T!ere is no state !ere it is not .ossible to mae ainal decision and rom !ic! transition can bemade to Commit"


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Atomic TransactionsCS-4513, D-Term 2007 1@

T!ree-

Coordinator sends !ote"e#uest(as beore*

> all .artici.ants res.ond airmati%ely,


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T!ree-

Coordinator bloced ineadystate

Sae to abort transaction

Coordinator bloced inPrecommitstate Sae to issue %lobal"Commit

Any cras!ed or .artitioned .artici.ants ill commit

!en reco%ered


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T!ree-

any inPrecommit, t!e mo%e toPrecommitstate

E


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T!ree-

> any .rocesses are inPrecommitstate,

t!en all cras!ed .rocesses ill reco%er toeady,Precommit, or Committedstates

> any .rocess is ineadystate, t!en all

ot!er cras!ed .rocesses ill reco%er toInit,Abort, orPrecommit

Sur%i%in' .rocesses can mae collecti%e decision


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Atomic Transactions in

Distributed Systems

CS-4513D-Term 2007

(Slides include materials rom Operating System Concepts, 7t!ed", by Silbers!at#, $al%in, & $a'ne,Modern Operating Systems, 2nded", by Tanenbaum, andDistributed Systems: Principles & Paradigms, 2nd

ed" y Tanenbaum and )an Steen*

Assumptions:

Graduate level

Operating SystemsMaking Choices aout operation systems

!hy a micro"century# $%ust aout enough time &or one

concept


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Deinition + Transaction

A seuence o o.erations t!at .erorm asin'le lo'ical unction

/am.les it!drain' money rom your account

ain' an airline reser%ation

ain' a credit-card .urc!ase

...

sually used in contet o databases


24/42


Deinition +Atomic Transaction

A transaction t!at !a..ens com.letely ornot at all

6o .artial results

/am.le Cas! mac!ine !ands you cas! and deducts amount

rom your account

Airline conirms your reser%ation and+ 8educes number o ree seats

+ C!ar'es your credit card

+ (Sometimes* increases number o meals loaded on li'!t


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Atomic Transaction 8e%ie

9undamental .rinci.les +A C I D+Atomicity+ to outside orld, transaction

!a..ens indi%isibly

+Consistency+ transaction .reser%es system

in%ariants

+Isolated+ transactions do not interere it!

eac! ot!er

+Durable+ once a transaction commits,t!e

c!an'es are .ermanent


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Distributed Atomic Transactions

Atomic transactions t!at s.an multi.le sitesand:or systems

Same semantics as atomic transactions on

sin'le system A C I D

9ailure modes Cras! or ot!er ailure o one site or system

6etor ailure or .artition y#antine ailures


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To-

Phase $:Coordinator+> any .artici.ant re.liesAbort(T*


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Atomic TransactionsCS-4513, D-Term 2007 @

To-


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Atomic TransactionsCS-4513, D-Term 2007

To-

coordinator .artici.ant

PREPARE


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9ailure 8eco%ery + To-

9ailure modes

(rom coordinators .oint o %ie*

+=n cras!

+'aitstate 6o res.onse rom some .artici.ant

to !ote"re#uestmessa'e

9ailure modes (rom .artici.ants .oint o %ie*

+=n cras!

+eadystate 6o messa'e rom coordinator to

%lobal"Abort(T* or %lobal"Commit(T*


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?ac o 8es.onse to Coordinator

!ote"e#uest(T* messa'e

/"'",+.artici.ant cras!

+6etor ailure

Timeout is considered eui%alent toAbort

+


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Coordinator Cras!

>ns.ect ?o'

>Abortor Commitstate+ 8esend corres.ondin' messa'e

+ Tae corres.ondin' local action

>Preparestate, eit!er+ 8esend !ote"re#uest(T* to all ot!er .artici.ants and

ait or t!eir res.onsesB or

+ nilaterally abort transaction >"e", .utAbort(T* in on lo' on stable store

Send %lobal"Abort(T* messa'e to all .artici.ants > not!in' in lo', abort transaction as abo%e


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6o 8es.onse to


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ns.ect local lo'+Commitstate

8edo:re.lay t!e transaction

+Abortstate

ndo:abort t!e transaction

+6o records about T

Same as local"abort(T*

+eadyState

Same as no res.onse toeady"to"commit(T* messa'e


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To-

idely used in distributed transaction anddatabase systems

$enerally ors ell

+!en coordinators are liely to reboot uicly

+!en netor .artition is liely to end uicly

Still subect to .artici.ant blocin'


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Atomic TransactionsCS-4513, D-Term 2007 1;

T!ree-

inor %ariation

idely uoted in literature

8arely im.lemented ecause indeinite blocin' due to coordinator

ailures doesnt !a..en %ery oten in real lie


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PREPARE

T!ree-

T!ere is no state rom !ic! a transition can bemade to eit!er Commitor Abort

T!ere is no state !ere it is not .ossible to mae a

inal decision and rom !ic! transition can bemade to Commit"


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Atomic TransactionsCS-4513, D-Term 2007 1@

T!ree-

Coordinator sends !ote"e#uest(as beore*

> all .artici.ants res.ond airmati%ely,


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T!ree-

Coordinator bloced ineadystate Sae to abort transaction

Coordinator bloced inPrecommitstate Sae to issue %lobal"Commit

Any cras!ed or .artitioned .artici.ants ill commit

!en reco%ered


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T!ree-

any inPrecommit, t!e mo%e toPrecommitstate

E


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T!ree-

> any .rocesses are inPrecommitstate,t!en all cras!ed .rocesses ill reco%er to

eady,Precommit, or Committedstates

> any .rocess is ineadystate, t!en all

ot!er cras!ed .rocesses ill reco%er to Init,Abort, orPrecommit

Sur%i%in' .rocesses can mae collecti%e decision

Atomic Transactions

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