Internet Scale Event Notification

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Internet ScaleEvent Notification

• David S. Rosenblum
• ICS Department
• Univ. of California, Irvine
• http//www.ics.uci.edu/dsr

Alexander L. Wolf CS Department Univ. of
Colorado, Boulder http//www.cs.colorado.edu/alw
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Acknowledgment

• Antonio Carzaniga(Politecnico di Milano and CU
  Boulder)
• Dennis Heimbigner(CU Boulder)
• Elisabetta Di Nitto(CEFRIEL and UC Irvine)
• Alfonso Fuggetta(Politecnico di Milano and UC
  Irvine)

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Some Statistics fromNetwork Wizards (www.nw.com)

• January 1998 Survey
• 29,669,611 hosts in DNS
• 5,331,640 of these reply to ping
• 204 active level 1 domains
• 781,602 level 2 domains
• 10,380,858 level 3 domains
• These are double the January 1997 survey numbers

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Attributes of Internet Scale

• Huge numbers of hosts and users
• Vast numbers of events
• Heterogeneity
• Increased importance of
• Network latency
• Autonomy
• Resource accounting
• Security
• Mobility

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Implications of Internet Scale on Event
Notification

• Event interaction becomes too burdensome for
  applications to manage on their own
• Thus, a separate event notification service is
  required
• But, event technologies originally designed for
  LANs dont scale

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What An Event Is Not
Common notions of event confound the
phenomenon, the representation, and the transport
of an event

• An event is not
• an object
• a message
• a notification

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What Is an Event?
Object of Interest
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What Is an Event?
Object of Interest
Invoker
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What Is an Event?
Object of Interest
Invoker
invocation
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What Is an Event?

• An event is the effect of the termination of an
  invocation of an operation on some object of
  interest

Object of Interest
Invoker
invocation
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What Is an Event?

• An event is the effect of the termination of an
  invocation of an operation on some object of
  interest
• Events occur regardless of whether or not theyre
  observed

Object of Interest
Invoker
invocation
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Event Notification
Interested Party
Event!
Object of Interest
Interested Party
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Event Notification
Interested Party
Object of Interest
Interested Party
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Event Notification Protocol
Interested Party
Object of Interest
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Event Notification Protocol
Interested Party
Advertise
Object of Interest
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Event Notification Protocol
Subscribe
Interested Party
Advertise
Object of Interest
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Event Notification Protocol
Subscribe
Interested Party
Advertise
Object of Interest
Publish
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Event Notification Protocol
Subscribe
Interested Party
Notify
Advertise
Object of Interest
Publish
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Event Notification Protocol
Subscribe
Interested Party
Notify
Unsubscribe
Advertise
Object of Interest
Publish
Unadvertise
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Event Notification Infrastructure
Interested Party
Object of Interest

• Provides
• Storage of advertisements
• Storage of subscriptions
• Efficient delivery of notifications

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Service Protocol Infrastructure

• Protocol developers exploit existing
  infrastructures
• e.g., new protocols exploiting Web servers
• Infrastructure providers must design a protocol
• e.g., CORBA Event Service based on RPC
• e.g., TIBCO based on publish/subscribe

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Other Critical Issues (I)

• Event observation
• Polling vs. announcing
• Extraction of event information
• Event naming
• Structure-based vs. content-based
• Pattern-matching and filtering
• Expressive power vs. efficiency

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Other Critical Issues (II)

• Time ordering
• Relativistic effects
• Availability of global clock
• Resource accounting
• Allocation of service costs
• Mobility of objects of interest and interested
  parties
• Efficient reconfiguration of service

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Conclusions

• Current technologies are optimized for special
  cases
• A single generator of events
• e.g., PointCast
• Event notification as a component of a single
  application
• e.g., CORBA Event Service
• Need better evaluation criteria
• Model problems, benchmarks, metrics,

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Additional Pointers

• Design Framework
• Rosenblum Wolf, A Design Framework for
  Internet-Scale Event Observation and
  Notification, Proc. ESEC/FSE 97, Springer LNCS
  1301
• SIENA
• Event service architectures
• JEDI
• Object-oriented event service for Java