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Small-Scale Peer-to-Peer Publish/Subscribe. Vinod Muthusamy, Hans-Arno Jacobsen University of Toronto July 17, 2005. P2PKM 2005 San Diego, CA. Motivation. Many distributed hash table (DHT)-based peer-to-peer applications Storage (OceanStore, Past) Database (PIER)

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small scale peer to peer publish subscribe

Small-Scale Peer-to-Peer Publish/Subscribe

Vinod Muthusamy, Hans-Arno Jacobsen

University of Toronto

July 17, 2005

P2PKM 2005San Diego, CA

motivation
Motivation
  • Many distributed hash table (DHT)-based peer-to-peer applications
    • Storage (OceanStore, Past)
    • Database (PIER)
    • Naming service (Chord-DNS)
    • Publish/subscribe (Scribe, P2P-ToPSS, Meghdoot)
  • Typically designed for and evaluated on a large-scale
  • Small-scale performance is important
    • Even large systems start small
    • Benefits even on small scale
  • Small-scale case study of a DHT-based pub/sub protocol

Small-Scale P2P Publish/Subscribe

agenda
Agenda
  • Background
    • Publish/subscribe model
    • Distributed hash tables
  • Small-scale benefits
  • Publish/subscribe on DHT
  • Evaluation
  • Conclusions

Small-Scale P2P Publish/Subscribe

publish subscribe model

Notification

Notification

Publish/subscribe model

TSX

Stock markets

NASDAQ

  • Simple interface
  • Decoupled interaction
  • Network efficiency

NYSE

Publisher

Publisher

AMGN=58

Publications

IBM=84

ORCL=12

JNJ=58

HON=24

INTC=19

MSFT=27

BrokerNetwork

Subscriptions

Subscriber

Subscriber

Subscriptions:

IBM > 85

ORCL < 10

JNJ > 60

Small-Scale P2P Publish/Subscribe

distributed hash tables
Distributed hash tables
  • Example: Pastry
  • Distributed version of a hash table data structure
    • Store (key, value) pairs
  • Each node receives at most K/N keys
  • Each node has about O(logN) routing state
  • Lookups resolved with O(logN) hops

Small-Scale P2P Publish/Subscribe

small scale benefits
Small-scale benefits

Small-Scale P2P Publish/Subscribe

service oriented architecture soa
Service oriented architecture (SOA)
  • An illustration of small-scale benefits
  • SOA: a distributed architecture
    • Loosely coupled reusable components
    • Enterprise service bus (ESB) comm. fabric
      • Can be realized as a pub/sub broker network
      • Pub/sub support in IBM Websphere, Sonic ESBs
  • Example
    • Three-tier Web server
    • Communication between components through pubs and subs
      • Decoupled interaction
      • Declarative bindings
    • Simple to add a Monitor component
      • Incremental service deployment
      • Late binding

Application

Server

Enterprise Service Bus

User

Products

Monitor

Database

Database

Small-Scale P2P Publish/Subscribe

pub sub case study
Pub/sub case study
  • P2P-ToPSS
    • A pub/sub system built over DHT
    • Large-scale performance previously studied [under submission]
  • Evaluate small-scale benefits (of the same algorithm) now
    • Subscription load balance

Small-Scale P2P Publish/Subscribe

distributed multidimensional matching dmm

Subscription

Publication

price < 50

weight > 50

price = 10

weight = 70

Distributed multidimensional matching (DMM)

1) Pub/sub domain:

3) Network domain:

-

0

1

2) Spatial domain:

100

00

01

10

11

01

11

0

1

weight

00

10

DHT network used to map from tree nodes to peers

0

0

price

100

Small-Scale P2P Publish/Subscribe

distributing the tree

peer-id

AF3483BQ1

hash

Region

weight

price

name/code

z-code

p_w_1101

1101

Distributing the tree
  • Let region r have z-code z, and tree node n(r)
  • Store n(r) at peer p(r), where p(r) is where DHT would store key z
  • Each peer performs mapping locally
  • Hash function ensures even distribution

Network

Subscription

price = …

weight = …

p/w

Small-Scale P2P Publish/Subscribe

load balancing
Load balancing
  • Peers can be overloaded due to
    • Excessive subscriptions storage
    • Excessive publication traffic
  • Overloaded peer delegates subscriptions to children in the DMM tree
    • A local decision

Network

0

00

01

p/w

Small-Scale P2P Publish/Subscribe

evaluation
Evaluation
  • SimPastry simulator (Microsoft Research)
    • Pastry DHT
    • Simulate network latencies, message costs
  • Nodes connected in a LAN
    • 1ms latency between every pair of nodes
  • Subscriptions
    • Attribute name + range
      • E.g.: “20 < weight < 40”
  • Metric
    • Storage load of subscriptions

Small-Scale P2P Publish/Subscribe

dht performance
DHT performance
  • 1000 random keys
  • DHT successfully balances load

Small-Scale P2P Publish/Subscribe

pub sub performance
Pub/sub performance

weight

price

  • 1000 fine-grained subscriptions
  • Load balancing distributes storage load

Small-Scale P2P Publish/Subscribe

pub sub performance1
Pub/sub performance

weight

price

  • 1000 coarse-grained subscriptions
  • Load balancing distributes but also increases storage load

Small-Scale P2P Publish/Subscribe

observation
Observation
  • Load balancing technique assumes available resources somewhere in the network
    • Leads to runaway subscription delegation
    • Common assumption in DHT applications
      • CAN DHT’s active caching and replication
      • Meghdoot’s hotspot circumvention
    • In DHT, no knowledge of aggregate available resources
  • Fundamental assumption of DHT applications not valid in small-scale networks

Small-Scale P2P Publish/Subscribe

conclusions
Conclusions
  • Pub/sub and DHTs
    • Proven benefits in large-scale network
    • Untapped benefits in small-scale networks
  • Common assumption on DHT applications
    • Sufficient available resources in the network
    • Small-scale networks break this assumption
  • Future work
    • Implement algorithms to estimate global resource availability
    • Curb runaway subscription delegation with this information
    • Evaluate other DHT applications in small-scale networks

Small-Scale P2P Publish/Subscribe

slide18
Q&A

Small-Scale Peer-to-Peer Publish/Subscribe

www.msrg.toronto.edu

Small-Scale P2P Publish/Subscribe