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Ungraceful. Procedures produce chkpnt independentlyDomino Results!. Next: Coordinated Blocking Chkpnt. Composed Blocking. Procedures are facilitated to frame a steady worldwide state, and
Transcripts
Slide 1

Conveyed Snapshots: Non-blocking checkpoint coordination convention Next: Uncoordinated Chkpnt

Slide 2

Uncoordinated Processes produce chkpnt freely Domino Results! Next: Coordinated Blocking Chkpnt

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Coordinated Blocking Processes are composed to shape a predictable worldwide state, and … * approve, channels flushed Ready! Go! initiator * p1 * p2 * p3 Next: Coordinated Blocking Chkpnt (cont " )

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Coordinated Blocking (cont\') Advantage Always reliable No Domino Effect Less capacity overhead Disadvantage Large dormancy to chkpnt! Next: Coordinated Non-blocking Chkpnt

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Coordinated Non-blocking Processes are composed, however … Do we truly need to square … ? ! Leslie Lamport K. Mani Chandy ! Next: Global-state Recording Algorithm

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Global-state Recording Alg. "Circulated depictions: deciding worldwide conditions of conveyed frameworks" , K. Mani Chandy and Leslie Lamport Step 1: prepare states Step 2: channel states Step 3: end of the calculation Next: Model of Distributed System

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c1 p q r c2 c3 c4 Model of Distributed System Processes Channels: coordinated, FIFO, blunder free Next: Step 1, handle states

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Step 1: handle states Initiator: Save its neighborhood state Send marker tokens on every cordial edge All different procedures: On accepting the main marker on any approaching edges, Save state, and spread markers on every friendly edge Resume execution. Facilitate markers will be eaten up. Next: Example

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c1 initiator c2 c3 c4 r p q marker checkpoint Example p x q x r Next: Proof

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x p q Proof Let us expect that a message m exists, and it makes our cut conflicting. p m q Next: Proof (cont " )

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x2 x x1 x p q [Incomplete page] Proof(cont\') p m x1 is the 1 st marker for process q x2 p m (2) x1 is not the 1 st marker for process q x1 q x2 Contradict the presumption. Next: Step 2, channel states

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Step 2: divert states p In-flight messages q Sent along the channel before the sender " s chkpnt Received along the channel after the recipient " s chkpnt Next: Example

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Example (2) p has recently spared its state (1) p is accepting messages r s q x 7 x 8 5 x 3 6 2 1 4 p x u t Next: Example (cont " )

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Example(cont\') p " s chkpnt activated by a marker from q r s x q x 7 1 2 3 5 4 6 7 8 p x 8 5 x 3 6 q 2 1 4 x p r x u s t x Next: Algorithm (changed)

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Algorithm (reconsidered) Initiator: Save its neighborhood state Send marker tokens on every single active edge All different procedures: On getting the principal marker on any approaching edges, Save state, and spread markers on every single active edge Resume execution, additionally spare approaching messages until a marker touches base through the channel Guarantees a steady worldwide state! Next: Step 3, end of the calculation

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initiator r p q Step 3: end of the calculation Did each procedure spare its state and in-flight messages? guide channel to the initiator? spreading over tree? General arrangement? Next: References

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References "Circulated depictions: deciding worldwide States of conveyed frameworks" , K. Mani Chandy and Leslie Lamport

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