SIENA: WideArea Event Notification Service

1
SIENA Wide-Area Event Notification Service

• Antonio Carzaniga
• David S. Rosenblum
• Alexander L. Wolf

2
Event Services Are Not New!

• Event models
• simple (UNIX signals)
• sophisticated (database triggers)
• Event notification services
• LAN message servers (e.g., SUN ToolTalk, DEC
  Fuse, HP SoftBench)
• USENET News (NNTP)
• Basic communication infrastructure
• point-to-point (TCP/IP, RPC, CORBA, RMI)
• multicast (MBONE)

3
Challenges

• Scalability
• many-to-many communications
• large number of objects and events
• decentralized control
• heterogeneous platforms and protocols
• Expressiveness
• rich event notification model
• expressive subscription language (an IP multicast
  address just doesnt cut it)
• Tradeoffs between scalability and expressiveness

4
SIENA Event Service
financial institution
NASDAQ
Event Service
object of interest
interested party
subscription
advertisement
NEW
subject stock name price
subject stock name MSFT
advertise
subscribe
unadvertise
unsubscribe
notification
Subject stock name MSFT price 123 diff
-1.0
publish
notify
5
Filters and Patterns
Pattern
Filter X price lt 5
time
publish
publish
publish
publish
publish
publish
publish
publish
publish
price2 stockMSFT date7.12.98
currLira qty4321
currLira qty4321 diff10
price3 stockDEC
price12 stockDEC
price1
price10
price2
price7
X
Y
Z
X price lt 5
XYZ
y
x
y
x
z
z
x
notify
notify
notify
price1
price2
price2 stockMSFT date7.12.98
currLira qty4321
currLira qty4321 diff10
price3 stockDEC
6
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7
Event Service Topologies
peer-to-peer acyclic graph
centralized
servers
clients
hierarchical
peer-to-peer generic graph
8
Subscription Forwarding

• subscriptions are forwarded to every server
• notifications follow (backwards) the paths set up
  by subscriptions

publish
notify
subscribe
9
Advertisement Forwarding

• advertisements are forwarded to every server
• subscriptions follow (backwards) and activate
  the paths set up by advertisements
• notifications follow the paths activated by
  subscriptions

advertise
publish
notify
subscribe
10
Optimization

• Multicasting is done downstream(closer to
  interested parties)

• Filters and patterns evaluated upstream(closer
  to objects of interest)

pattern assembly ABAB
multicast of notification
X
A
advertisement
subscription
advertisements
X
A
AB
X
B
B
subscriptions
AB
AB
A
X
A
AB
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12
Design Validation

• Problem validation of server topologies and
  routing strategies with respect to
• network traffic
• memory usage
• CPU usage
• SIENA approach simulation

13
Parameters for Simulations

• Network
• topology, latency, bandwidth, cost function
• Servers
• location, topology, routing strategy
• Objects of interest and interested parties
• number, location, primary server, behavior

14
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15
Prototype

• C/Java servers
• C/Java client interface
• XML data representation
• Several communication protocols
• SMTP (e-mail), HTTP, plain TCP/IP

16
Conclusions

• SIENA is an architecture that implements a
  scalable and flexible event service
• event service interface
• notification model
• service topologies
• notification dispatching strategies
• validation through simulation
• prototype