Pablo Chacin (Polytechnic University of Catalonia, Spain): Utility Driven Service Routing over Large Scale Infrastructures
1. Utility Driven Service Routing
over Large Scale Infrastructures
Pablo Chacin
Polytechnic University of Catalonia
(UPC), Spain
2. Authors
• Pablo Chacin, Polytechnic University of
Catalonia, Spain (UPC)
• Leandro Navarro, UPC
• Pedro Garcia López, Rovira i Virgili
University, Spain
3. Key Points
• UDON is an Utility Driven Overlay Network for routing
service requests to service instances that match some QoS
requirements
• It is aimed for highly dynamic large-scale shared
infrastructures.
• Combines an application provided utility function to express
QoS with an epidemic protocol to disseminate the
information that supports the routing
• Experimental analysis shows that UDON allocates requests
meeting QoS with a high probability and low overhead; it is
scalable, robust and adapts well to a wide range of
conditions.
13-15 December 2010 ServiceWave 2010
4. Outline
• Defining the problem context
• Design principles
• Experimental evaluation
• Conclusions
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5. Internet of Services
Source: Schroth, C., Janner, T.: Web 2.0 and soa: Converging concepts enabling
the internet of services. IT Professional 9(3), 36–41 (May/June 2007)
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7. Challenges
• Non dedicated Servers
– The QoS a server can offer is hard to predict
• Fluctuations in the demand
• Different QoS requirements for different users
– e.g. free/paid; bronze/silver/gold
• Large scale
• Number of instances may vary
– Activations/deactivations due to fluctuations on the
demand
– Failures
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8. Guiding principles
• Decentralized decisions using local information
– No global view; no single point of failure; more
scalable and adaptable
• Representation of QoS as an Utility Function
– Compact representation
– Facilitate comparisons despite heterogeneity
• Model-less adaptation
– No need to elicit or learn a performance model for
the systems
– If information is not exact, rationality may not
help.
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10. Utility Function
• In economics, utility is a
measure of relative
satisfaction
• Summarizes multiple
attributes into a single
scalar value
– F(a1,..an) → [0,1]
• Facilitates comparison,
allow private evaluations
Cobb-Douglas utility function
U(t,c) = t(ac(1-a)
t = execution time
c = cost
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11. Epidemic Overlay
• Simple maintenance algorithm
– Each node has a local view of
the state of a set of neighbors
– Periodically choses some
neighbors and sends its local
view + own state
– Each node merges its local
view with the received views
keeping the most recently
updated entries
• Disseminates information with low
overhead
• Highly scalable and resilient
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12. Randomized Greedy Utility
Routing
• Multi-hop routing using local
information
– On each hop, ranks
neighbors based on its
(potentially outdated)
utility
– Forward to the node with
a probability based on
ranking
• Simple concept. Allows
multiple heuristics for Image source: physics.org
ranking (evaluation is an Greedy Routing Enables Network Navigation
Without a 'Map'
ongoing work) http://www.physorg.com/news154093231.html
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14. Simulation Model
• Network topology is abstracted
– One single cluster, 1000's of servers.
– Constant, negligible delays
• Utility Function simulated as a Random Process
– Make evaluation more general, not tied to a
particular utility definition
– Evaluate the effect of different parameters
• Compared with other overlays of the same family
– Random: no organization (baseline)
– Gradient: keep instances with similar QoS close
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15. The Simulation of the Utility
Function
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16. Metrics
• Overlay (information dissemination)
– Age: how old is the information in the
local view (average)
– Staleness: how accurate is the local view
with respect of real current information
• Routing
– Satisfied demand: how effective and
reliable is the allocation (% of success)
– Hops: how efficient
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17. Overlay
Maintains “fresh”
information
Minimizes
staleness
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18. Performance
Tolerance: maximum allowed difference
between required QoS and node's utility: Allocates requests with high
~ 1.0 any node with a higher utility matches probability, and low number or
~ 0.0 only node with the exact demanded
utility matches hops, even under very
demanding search criteria (low
tolerance)
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19. Performance looking for
scarce resources
Allocates requests
even when target
nodes are scarce.
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20. Churn
Performance
“gracefully” degrades
under high churn
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21. Variation in Utility
Allocates requests even under
highly fluctuating conditions.
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22. Sensitivity to Operational
Parameters
Optimal setup demands low
communication overhead
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24. Conclusions
• Simple, principled solution for routing requests
over large-scale cluster-based web services on
shared infrastructures
• UDON meets requirements on scenarios of
interest and shows desirable properties
– Effective
– Low overhead
– Scalable
– Very adaptable
– Robust
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25. (Near) Future work
• Apply UDON to A concrete scenario
– Simulated cluster based web services
– Use concrete utility functions
• Evaluate alternative routing heuristics
• Propagate information based on usefulness:
see which QoS are more demanded and
propagate information of nodes that offer it
with higher probability
• Consider locality when selecting neighbors to
adapt to wide area distributed clusters (multi-
site)
13-15 December 2010 ServiceWave 2010