JBora Reliable Group Communication Middleware

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JBora Reliable Group Communication Middleware

• Alberto Bartoli
• Etienne Antoniutti Di Muro
• Milan Prica
• Università degli Studi di Trieste, Italy

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What is JBora?

• JBora is the user application interface towards a
  replication layer
• Built on top of Spread Group Communication tool
• JBora is a shared object amongst all application
  threads within the same VM

Programmer Code
JMiramare
JBora
Spread
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What Can You Do With JBora ?

• Usual things
• Join a group
• Multicast message and receive events
• Leave a group
• Inter-thread communication(useful when
  interacting with external channel, e.g. HTTP)
• localCall() and localRespond() novel primitives
• Share application level information, among
  replicas, i.e. load information, sensor data
• WhiteBoard object shared among group members

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JBora Reliability Guarantees

• ? Total Order Uniform Delivery
• In Partitionable Systems
• Without Transitional Views
• Not going to discuss this in detail

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JBora Group Communication Performance

• No Free Lunch
• GC powerful but costly
• Likely to be a key bottleneck
• Objective
• Can we shift the GC-induced bottleneck upto
  higher throughput values ?

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Methodology Message Packing (I)
Traditional (Standard)use of Group
Communication
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Methodology Message Packing (II)
Message Packing(Friedman, Van Renesse 1996)
buffered
buffered
buffered
buffered
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JBora Key FeatureAdaptive Message Packing

• Message buffer is transmitted when sending
  conditions have been satisfied
• packing interval has elapsed
• packing degree has been reached
• packing dimension has been reached
• Each parameter may be kept constant or varied at
  runtime

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JBora Key FeatureAdaptive Message Packing

• We have seen that with suitable values we can
  have very good performance
• The problem is how to tune this once and for all
  ?
• Idea! Enable the system to tune itself
  automatically and adaptively

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What is a Policy?

• A policy is a pluggable module that enables to
  obtain adaptive behaviour
• Run-time access to performance related sensors
• Modifies packing parameters accordingly

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JBora Adaptive Message Packing Performance

• Throughput vs. clientstest application - 3
  replicas

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Policy Implementation Notes

• interface DynamicPacking void
  applyPolicy(PackingConfiguration,int)
• PackingConfiguration class that handles message
  packing parameters
• int table of sensor measurements, one row
  per sensor

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Policy Examples

• Constant policy Dummy Policy . Keeps message
  packing parameters constant, as defined at
  configuration time.
• Max Throughput policy Accesses throughput sensor
  measurements, and adjusts message packing degree
  in order to increase message throughput.
• CPU policy Accesses CPU sensor measurements,
  and adjusts message packing degree in order to
  decrease CPU usage

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Open Issues

• Latency issues

Latency vs. clientstest application - 3 replicas
Packing Degree 10

• Tailoring policies to the application
• Developing new sensors is it worthy ?

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JBora Configuration

• JBora adaptability parameters
• packing interval
• packing degree
• packing dimension
• policy module class name
• Where to put the configuration file ?
• Who handles configuration parameters DOM ?

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Questions ?
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