multi-resource allocation with unknown participants
DESCRIPTION
Multi-resource Allocation with Unknown Participants. Ajoy K. Datta , Stéphane Devismes, François Kawala , Lawrence L. Larmore , and Maria Potop-Butucaru. K-resource Allocation. C 1. N >> M. C 2. R 1. C 3. R 2. C 4. …. C 5. R M. C 6. …. Resources. C N. Clients. - PowerPoint PPT PresentationTRANSCRIPT
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Multi-resource Allocation with Unknown Participants
Ajoy K. Datta, Stéphane Devismes, François Kawala, Lawrence L.
Larmore, and Maria Potop-Butucaru
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PDAA'2011, Osaka
K-resource Allocation
December 2, 2011
C1
C2
C3
C4
C5
C6
CN
Clients
R1
… Resources
R2
RM
…
• N >> M
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PDAA'2011, Osaka
K-resource Allocation
December 2, 2011
C1
C2
C3
C4
C5
C6
CN
Clients
R1
… Resources
R2
RM
…
• N >> M
• Clients don’t know each other
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PDAA'2011, Osaka
K-resource Allocation
December 2, 2011
C1
C2
C3
C4
C5
C6
CN
Clients
R1
… Resources
R2
RM
…
• N >> M
• Clients don’t know each other
• Request: up to K resources
• Clients only know the IDs of the resource they request
• Request given by an oracle
R1, R2
R1, R3
R4
R2, R6, R7
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PDAA'2011, Osaka
K-resource Allocation
December 2, 2011
C1
C2
C3
C4
C5
C6
CN
Clients
R1
… Resources
R2
RM
…
R1, R2
R1, R3
R4
R2, R6, R7
SAFETY: Each resource is used by at most one client at a time
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PDAA'2011, Osaka
K-resource Allocation
December 2, 2011
C1
C2
C3
C4
C5
C6
CN
Clients
R1
… Resources
R2
RM
…LIVENESS:
Every request is eventually satisfied
R1, R2
R1, R3
R4
R2, R6, R7
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PDAA'2011, Osaka
Related Work
• K-out-of-L Exclusion• Drinking philosophers
• Application: Peer-to-Peer systems
December 2, 2011
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PDAA'2011, Osaka
Model
December 2, 2011
• Asynchronous message passing
• Reliable link
•Any client can only communicate with the resources it requests
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PDAA'2011, Osaka
2-Resource Allocation
• Overview– Queues• At each resource• To store client’s requests• The request at head of the queue is satisfied
• Issue– Deadlock
December 2, 2011
C3
C1
C2
R5
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PDAA'2011, Osaka
2-Resource Allocation
December 2, 2011
R1
R3R2
C1 C2
C3
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PDAA'2011, Osaka
Deadlock
December 2, 2011
C2
C1
R1
C3
C2
R3
C1
C3
R2
C1 C2
C3
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PDAA'2011, Osaka
Our solution
• First request: strong• (Second request: weak)• Two queues per resource: strong, weak• Resource allocated to the head of its strong
queue• Weak requests move from weak to strong
queue– Under some conditions
December 2, 2011
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PDAA'2011, Osaka
Our solution
December 2, 2011
R1
C1
R2
C1,R1,Weak
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PDAA'2011, Osaka
Our solution
December 2, 2011
R1
C1
R2
C1
C1,R2,Strong
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
R2
C1
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
R2
C1
StrongReady
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
C1
R2
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
C1
R2
ResAllowed
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
C1
R2
CS
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
C1
R2
Done
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PDAA'2011, Osaka
Our solution
December 2, 2011
C1
R1
C1
R2
Done
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PDAA'2011, Osaka
Our solution
December 2, 2011
R1
C1
R2
EndAck
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PDAA'2011, Osaka
Deadlock
December 2, 2011
C3
R3
C2C2
R2
C1C1
R1
C3
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PDAA'2011, Osaka
Deadlock
December 2, 2011
C3
R3
C2
C2
R2
C1
C1
R1
C3
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PDAA'2011, Osaka
Dependancy Cycle
December 2, 2011
C3
R3
C2
C2
R2
C1
C1
R1
C3
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PDAA'2011, Osaka
Conflict Resolution
• Dependency cycle detection– A message follows the dependencies
• Dependency cycle breaking– A dependency is broken– A client’s request is penalized
December 2, 2011
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PDAA'2011, Osaka
Fairness
• Penalization must be fair– Identifiers cannot be used
• We use a token – circulating on the resource ring
December 2, 2011
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PDAA'2011, Osaka
Token (1/2)
• Token reception– The resource marks all its strong requests
• Token releasing– When all marked request have been satisfied– Forwarded to the next resource in the ring
• Each resource gets the token infinitely often
December 2, 2011
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PDAA'2011, Osaka
Token (2/2)
• Token holder never penalized• Penalized dependency: – the one out-coming from the smallest non token
holder• The token holder “flushes” its “old” requests
before releasing the token
December 2, 2011
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PDAA'2011, Osaka
Dynamicity
• Join– New identity
• Leave– With announcement: easy– Crash• Need a participant detector
December 2, 2011
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PDAA'2011, Osaka
Participant Detector
• Required : Perfect [Fetzer,2003]
– Strong completeness: Every client that leaves tge system is eventually removed from the participant lists
– Strong accuracy: No client can be removed from a list before it leaves the system
December 2, 2011
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PDAA'2011, Osaka
K > 2
• Generalized the previous solution: hard
• Pessimistic approach: prevent deadlock creation– Resource allocated sequentially– Not efficient (not enough concurrency)
• Hybrid solution ?
December 2, 2011
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PDAA'2011, Osaka
Thank youDecember 2, 2011