Robust Reconfigurable Erlang Component System ErlCOM

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Robust Reconfigurable Erlang Component
SystemErlCOM

• Gabor Batori, Zoltan Theisz, Domonkos Asztalos
• ETH Software Engineering Group

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Why?

• Robust
• Fault tolerant, Highly available
• Reconfigurable
• Adaptability to environmental changes
• Erlang
• Ericssons preferred language ?
• Component
• Separation of functionality
• Structured, reusable code
• System
• Application neutral framework

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Component Model

• Component, Composite Component Functionality
  Owner
• Interface, Receptacle Interaction Point Owner
• Binding Communication Owner
• Component Framework Constraint Owner

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Robust Component Model

• Capsule Supervision Owner
• Caplet Component Owner
• Component Functionality Owner

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Reconfiguration

• Reactive behavior
• Due to environmental changes (switch-over)
• Due to HW/SW faults (fail-over)
• Implementation
• Reflectivity (observable)
• Operational Facility (dynamic reconfiguration)

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Basic concepts
Concept Erlang ErlCOM
Concurrent entity Process Component
Communication Message Passing Binding
State Local state information Reflective Repository

• No reasoning about messages
• Interception consists of pre/post actions ?
  synchronous communication

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RUNES Example

• Gateways represented by Capsules (running Erlang)
• Middleware and Application Component Frameworks
  using the services of the Ubiquitous CRTK

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Erlang Mapping

• Component ? gen_server
• Interface/receptacle ? gen_server
• Binding ? gen_server
• Pre/post action ? process
• Capsule ? erlang node, gen_server
• Caplet ? gen_server, supervisor
• Reflective Repository ? mnesia
• CRTK ?module (floating reflective API)

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Implementation details(1)

• Entity Relationship Diagram (ERD) generated
  Erlang Code

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Implementation details(2)

• Message Sequence Chart (MSC) Erlang Code (CRTK)

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What we have learnt?

• Entity Relationship Diagram helps identify
  concepts
• MSC helps describe dynamics
• Erlang provides versatile platform for component
  based systems
• Current implementation provides a feasible proof
  of concept for RUNES CRTK.
• BUT, the implementation code is COMPLEX

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How to reduce complexity?

• Custom libraries (API design)
• Code maintenance problem (version handling)
• Custom behavior (language design and virtual
  machine)
• Too intrusive , too costly
• Generative Programming (meta-modeling, modeling
  and transformation design)
• New design approach ? Domain Specific Language
  engineering and supporting IDE needed

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Our solution

• Development cycle

Translator (Erlang Templates)
ERD,MSC
Generates
ErlCOM Structural Description
Application Code (Erlang)
Application (Erlang)
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Generic Modeling Environment (GME)

• NOT object-oriented, NOT UML
• Supports multi domain modeling
• Meta-model aware graphical editor
• Supports transformation frameworks
• Freely available, Open Source, BUT industry
  quality
• Perfect match to Erlang ?

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Conclusion

• ErlCOM extends Erlang with new abstractions (like
  OTP)
• ErlCOMs Component System provides adaptive
  behavior to Erlang applications in Run-Time
• ErlCOMs GME IDE allows design abstraction driven
  Erlang code production in Development-Time
• Should not be used in application development
  where the Erlang abstraction level is perfectly
  sufficient (ErlCOM is a component based adaptive
  extension)