A framework for collaborative distributed simulation over the grid
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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 l.jpg

A Framework for Collaborative Distributed Simulation over the Grid

Stephen John Turner

Parallel & Distributed Computing Centre

Nanyang Technological University

Singapore


Outline l.jpg
Outline the Grid

  • 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 l.jpg
Distributed Simulation the Grid

  • 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 l.jpg
Example Application Areas the Grid

  • 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 l.jpg

Federation the Grid

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 l.jpg
High Level Architecture the Grid

  • 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 l.jpg
Grid Computing the Grid

  • 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 l.jpg
Grid Computing the Grid

Web Services

Grid Services

OGSA

OGSI

Globus Toolkit

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Motivation l.jpg
Motivation the Grid

  • 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 l.jpg
Motivation the Grid

  • 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 l.jpg

Resource the Grid

Managem’t

Semantic Interfaces

Policies

Workflow

Security

Service/ModelDiscovery

Service/ModelComposition

Execution

Simulation Life Cycle

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Research challenges l.jpg
Research Challenges the Grid

  • 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 l.jpg
Research Challenges the Grid

  • 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 l.jpg
Research Challenges the Grid

  • 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 l.jpg
Research Challenges the Grid

  • 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 l.jpg

Main work the Grid

Security

Service/ModelDiscovery

Service/ModelComposition

Execution

Simulation Life Cycle

Resource

Managem’t

Semantic Interfaces

Policies

Workflow

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Hla based distributed simulation l.jpg

RTI the Grid

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 l.jpg

5 the Grid

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 l.jpg

4a the Grid

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 l.jpg

Load Management System (LMS) the Grid

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 l.jpg

Load Management System (LMS) the Grid

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 l.jpg

LMS the Grid

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 l.jpg

LM the Grid

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 l.jpg
Federate the Grid

  • 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 l.jpg
Load Manager the Grid

  • 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 l.jpg
Migration Approaches the Grid

  • Federation wide synchronization

federate

federate

federate

Federation-Wide Save

Federate Migration

Federation-Wide Restore

Costly Operation!

Brunel


Migration approaches27 l.jpg

federate the Grid

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 l.jpg
Our Approach the Grid

  • 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 l.jpg
Federate Migration the Grid

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

Brunel


Experimental results l.jpg
Experimental Results the Grid

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Grid enabled hla rti l.jpg

Resource the Grid

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 l.jpg
Design the Grid

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

Brunel


Discussion l.jpg
Discussion the Grid

  • 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 l.jpg
Conclusions the Grid

  • 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 l.jpg
Conclusions the Grid

  • 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 l.jpg

Thank you for your attention! the Grid

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


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