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A Framework for Collaborative Distributed Simulation over the Grid. Stephen John Turner Parallel & Distributed Computing Centre Nanyang Technological University Singapore. Outline. Background Distributed Simulation Grid Computing Motivation Research Challenges

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a framework for collaborative distributed simulation over the grid

A Framework for Collaborative Distributed Simulation over the Grid

Stephen John Turner

Parallel & Distributed Computing Centre

Nanyang Technological University

Singapore

outline
Outline
  • Background
    • Distributed Simulation
    • Grid Computing
  • Motivation
  • Research Challenges
  • HLA-based Distributed Simulation
    • Grid Services and Service Discovery
    • Load Management System
    • Grid Enabled HLA/RTI
  • Conclusions

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distributed simulation
Distributed Simulation
  • Provides a way of linking simulation components (federates) of various types at possibly different locations to create a common virtual environment (federation)

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example application areas
Example Application Areas
  • Battlefield Simulation
    • Linking different types of forces at multiple physical locations to create a realistic and complex virtual world
  • Supply Chain Simulation
    • Managing material and information flow, from manufacturers through distributors to customers
  • Air Traffic Control
    • Simulating airports and airspace sectors to provide faster than real-time simulation for “what-if” analysis
  • Multi-player Internet Games
    • Involving massive multi-player (~10,000) virtual world

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high level architecture

Federation

SOM

SOM

SOM

SOM

SOM

SOM

SOM

SOM

FOM

SOM

HLA Rules

(Federations)

HLA Rules

(Federates)

SimulationSurrogates

Passive Viewers

Simulations

Interface

FED

Run-Time Infrastructure (RTI)

Federation Management Declaration Management

Object Management Ownership Management

Time Management Data Distribution Management

High Level Architecture

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high level architecture6
High Level Architecture
  • Features of High Level Architecture
    • Each federate has a simulation object model (SOM) defining the data to be shared with other federates allowing reuse in different federations
    • The federation (set of federates) has a common federation object model (FOM)
    • HLA supports distributed simulations linking the federates of a federation over a LAN or the Internet
    • Time Management can be used to ensure the correct ordering of events
    • HLA is an IEEE (1516) and OMG standard

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grid computing
Grid Computing
  • Grid technology is the next step in the evolution of computing, enabling new forms of collaboration through the seamless sharing of distributed computing and data resources

Communities can share geographically distributed resources for their common purpose

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grid computing8
Grid Computing

Web Services

Grid Services

OGSA

OGSI

Globus Toolkit

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motivation
Motivation
  • Collaborative Simulation Development
    • The development of complex simulations usually requires collaborative effort from analysts with different domain knowledge and expertise, possibly at different locations
  • Sharing of Computing Resources
    • Simulation systems often require huge computing resources and the participants in the simulation and/or data sets required may also be geographically distributed

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motivation10
Motivation
  • HLA-based Distributed Simulation on the Grid
    • HLA defines a standard for reuse and interoperability
    • Grid technologies enable collaboration and the use of distributed computing resources
  • Collaborative
  • Distributed
  • Complex & Multi-dimensional

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simulation life cycle

Resource

Managem’t

Semantic Interfaces

Policies

Workflow

Security

Service/ModelDiscovery

Service/ModelComposition

Execution

Simulation Life Cycle

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research challenges
Research Challenges
  • Service/Model Discovery
    • Based on requirements, “suitable” component models are selected to form an overall simulation
    • Research Issues
      • How are simulation models registered as grid services
      • How are simulation models discovered?
      • How are the interfaces defined?
      • Are the simulation models HLA compliant?
      • Do they conform to any standard reference models (e.g. HLA-CSPIF)?

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research challenges13
Research Challenges
  • Service/Model Composition
    • Checking semantic interoperability between individual component simulation models from different sources
    • Research Issues
      • Can the output of one simulation model feed into the input of another?
      • How is the work flow of the configuration described?
      • What are the mechanisms for verifying the correctness of the simulation?

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research challenges14
Research Challenges
  • Security
    • Simulation partners should be allowed to specify selective access to their simulation models
    • Research Issues
      • Does a user have access to a particular simulation model or data?
      • Can a user selectively share sensitive data with different partners?
      • Does the simulation model originate from a trusted partner?
      • Must the model be executed on a particular resource?

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research challenges15
Research Challenges
  • Execution
    • Simulation partners may obtain computing resources from the Grid to supplement their needs
    • Research Issues
      • How can the different simulation runs be partitioned onto the available computing resources?
      • What mechanisms should be used for scheduling and load management of simulations on the Grid?
      • What kind of fault tolerance mechanisms are required?

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simulation life cycle16

Main work

Security

Service/ModelDiscovery

Service/ModelComposition

Execution

Simulation Life Cycle

Resource

Managem’t

Semantic Interfaces

Policies

Workflow

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hla based distributed simulation

RTI

RTI

RTI

Model Factory

Model Factory

RTI

RTI

federate

federate

federate

federate

federate

HLA-based Distributed Simulation
  • Discovery and Composition of Models
  • Discovery of Resources
  • Management of Simulation Execution

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grid services and service discovery

5

1

2

4

3

Grid Services and Service Discovery
  • Query Index Service for RTI Service handle for federation
  • Create RtiExec if necessary and get endpoint used by RtiExec
  • Query Index Service for Federate Factory Service handle
  • Create Federate Service and Federate Process
  • Federate Processes join federation

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grid services and service discovery19

4a

5

4

3

Grid Services and Service Discovery
  • Query Index Service for Federate Factory Service handle
  • Create Federate Service and Federate Process
  • 4a.Federate Service can query Index Service for RtiExec endpoint
  • 5. Federate Processes join federation

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load management system

Load Management System (LMS)

SimulationSurrogates

Passive

Viewers

Simulations

Interface

SimulationSurrogates

Interface

Passive

Viewers

Simulations

Run-Time Infrastructure (RTI)

Interface

Federation Management Declaration Management

Object Management Ownership Management

Time Management Data Distribution Management

Run-Time Infrastructure (RTI)

Federation Management Declaration Management

Object Management Ownership Management

Time Management Data Distribution Management

Load Management System
  • Use Grid software for
  • Authentication,
  • Resource Discovery, Allocation & Monitoring, and
  • Facilitating Federate Migration

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load management system21

Load Management System (LMS)

Load Management System (LMS)

Load Management System (LMS)

federate

federate

federate

federate

federate

federate

federate

federate

federate

federate

federate

federate

federate

federate

High Speed Myrinet Switch

Load Management System (LMS)

Load Management System (LMS)

Load Management System

Resource Discovery

Allocation & Monitoring

Globus

Run Time Infrastructure

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simkernel

LMS

Simulation

Code

FederateAmbassador

LMClient

RTIambassador

federate

RTI

Shared

Data

SimKernel
  • Simulation code extended with two interfaces:
  • One for communicating with Runtime Infrastructure (RTI)
  • One for communicating with Load Management System (LMS)

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simkernel23

LM

Sub-

Model

Sub-

Model

Sub-

Model

LMClient

LMClient

LMClient

federate

federate

federate

SIMKernel

SIMKernel

SIMKernel

RTI

map

SimKernel

Design

Implementation

Execution

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federate
Federate
  • Each federate contains two threads: (SimKernel) and load management thread (LMClient)
    • SimKernel processes simulation events as defined by the user and communicates with RTI
    • LMClient works with Load Manager (LM) to perform federate migration
      • receive instruction from LM
      • stop SimKernel
      • get SimKernel execution state
      • transfer SimKernel configuration and execution state

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load manager
Load Manager
  • Load Manager
    • Constantly monitors and collects load information of each individual participating computing node
    • Runs load balancing algorithm to determine which federate should migrate from which host to which destination
    • Communicates with the LMClients at both the source and destination hosts until migration succeeds

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migration approaches
Migration Approaches
  • Federation wide synchronization

federate

federate

federate

Federation-Wide Save

Federate Migration

Federation-Wide Restore

Costly Operation!

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migration approaches27

federate

federate

federate

Migration Approaches
  • Communication among federates:
    • Messages may be lost in transit during migration

publish

subscribe

msg

network

resign

join

subscribe

subscribe

unsubscribe

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our approach
Our Approach
  • We developed an algorithm aiming to:
    • Provide transparent migration, and
    • Minimize the migration overhead
  • Run two instances of the migrating federate until event integrity is ensured
  • No synchronization or FTP communication is required
  • Implementation is specific to federates based on SimKernel

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federate migration
Federate Migration

migrating

federate

sendOutgoingEvents

returnStatus

resignFederationExec

suspend

missingMsg

receivedInteraction

flushQueueRequest

receivedInteraction

collect

returnStatus

LMClient

@source

Req_migrate

migrationSucceeded

notifyMissingMsg

returnInformation

returnInformation

requestInformation

RTI

Load Manager

joinFederation

pub/sub Interaction

flushQueueRequest

receivedInteraction

Req_migrate

getMsgCount

recvMsgCount

LMClient

@destination

resume

restore

new

restarting

federate

Latency period

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grid enabled hla rti

Resource

RtiExec

FedExec1…m

Proxies…

Grid Enabled HLA/RTI

Client 1

Client 1

Grid Network

Client n

Client n

Federation 1

Federation m

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design
Design

Grid Services: indexing, discovery, resource management, monitoring services …

Grid Services

Globus

Proxy

Simulation Code

Proxies & Federates

Grid-enabled API

HLA API

Grid-enabled HLA API

HLA API

Globus

RTI on LAN

Globus

Grid Network

Client

Resource

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discussion
Discussion
  • Advantages
    • Avoids some firewall issues as client communicates with proxy via grid services
    • Client application code can run on heterogenous platforms
    • Provides easy migration of client code, proxy does not need to be migrated
  • Disadvantages
    • Overhead of communication as all simulation events use grid services

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conclusions
Conclusions
  • Work Done:
    • Developed a simple prototype using Globus for resource discovery, allocation and federate deployment (DS-RT ’02)
    • Developed SimKernel framework to allow modeler to concentrate on the simulation, rather than implementation (DS-RT ’03)
    • Developed a federate migration protocol without using federation synchronization (ICCS ’04)
    • Developed Grid Service and Service Discovery Framework (submitted to DS-RT ‘04)

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conclusions35
Conclusions
  • Future Work:
    • Service/model discovery
    • Service/model composition
      • Grid workflow languages
    • Grid enabled HLA/RTI
      • Performance measurement
      • Alternative communication mechanisms
      • Migration and fault tolerance
    • Integration of sub-projects
      • Convert to GT4 (WS-RF)

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thank you for your attention

Thank you for your attention!

Questions & Answers

While the HLA defines a standard for the construction of large-scale distributed simulations, Grid technologies enable collaboration and the use of distributed computing resources, while also facilitating access to geographically distributed data sets