Extended Engine

1
Components of Mozart Implementation
Extended Engine
DMM Distributed Memory Managem.
Marshaler
Protocol Layer
Network Layer
2
Implementation Architecture-1

• Extended Engine
• Virtual Machine for local execution
• Extended for distribution
• Does not handle operations on distributed
  entities
• Protocol Layer
• Entity-specific protocols for network-transparent
  distributed entities.
• Examples mobile object protocol, variable
  protocol

3
Implementation Architecture-2

• Marshaler (Serialization)
• Unmarshaling too.
• Serialization of language graphs
• Constructor of language graphs
• Distributed Memory Management
• Distributed garbage collection
• Mappings between local representative and
  distributed (global) name
• Globalization/localization

4
Network Layer

• Multiplexing - at most one TCP-connection between
  any 2 sites irrespective of number of shared
  entities
• Graceful degradation - sharing limited
  OS-resources, i.e. connections transparently on
  high demand (fair between threads)
• Flow control feedback to asynchronous
  message-passing
• Recovery on network-partitioning (when wanted)
• Buffering before marshaling

5
Components of Mozart Implementation
Extended Engine
DMM Distributed Memory Managem.
Marshaler
Protocol Layer
DISTRIBUTION LAYER
Network Layer
6
Extending the Engine
Core Engine

• Core vs. Extended
• Outgoing arcs
• new native functionality
• Ingoing arcs
• hooks into virtual machine

7
Properties of a good core VM

• From Distribution point-of-view
• Concurrency
• lightweight threads and scheduler
• fine-grained suspension
• All entities are first class
• integrate deal with code/data

8
Entity extensions

• Distribution tuning
• mobile vs. stationary
• lazy vs. eager
• Failure extensions
• how to behave on different failure conditions
• e.g. object-state permanently lost
• e.g. object-state temporarily lost - network
  partitioning.
• Security extensions

9
Extended Engine

• Basic operation on distributed entity returns one
  of
• suspends (executing thread)
• continue
• exception
• Language extensions e.g
• connection (tickets)
• explicit mobility
• best if engine open to extension
• Engine extended to be suspendable on all
  operations

Protocol Layer
10
Examples

• Basic operation return values
• remote stationary distributed object
• suspends
• exception (failure)
• state access/update on mobile distributed object
• suspends
• continue
• exception
• asynchronous message sending
• continue
• exception
• suspends (flow control!!)

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Extended Engine

• Activate Thread

Protocol Layer
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Extended Engine

• Distributed IO slot
• Engine scheduler top-level
• Threads(computation)
• Distributed IO
• Other IO
• Engine scheduler for threads
• Fairness
• Priority

Network Layer
13
Extended Engine
Distributed Memory Management

• Globalize/localize entity
• Failure watcher activation
• Garbage collection
• additional root
• liveness inquiry

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Extended Engine
Distributed Memory Management

• Garbage Collection
• Entity locally accessible
• Provide gc-roots
• Centralized GC collection done

15
Marshaler
Extended Engine

• Builder routines
• constructors for all language entities
• Decompose routines
• inverse of the above

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Marshaler
Extended Engine

• Pickling
• marshaling stateless entities to file
• Persistence
• marshaling system snapshot to file

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Virtual Machine for Distribution

• VM handles centralized computation
• Minimal set of hooks into VM to achieve
  distribution
• Hooks not for the application programmer
• lower level
• without safety net

VM