Applied Architectures

Eunyoung Hwang

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Objectives

• How principles have been used to solve challenging problems

• How architecture can be used to explain and analyze common commercial systems

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Outline

• Distributed Network-based Applications– Limitations– REST– Commercial Internet Scale Applications: Google

• Decentralized Architecture– Grid Computing– Cloud Computing– Peer-2-Peer: Napster, Grutella, Skype

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Fallacies of Distributed Systems Viewpoint

• The network is reliable• Latency is zero• Bandwidth is infinite• The network is secure• Topology does not change• There is one administrator• Transport cost is zero• The network is homogeneous

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WWW Architecture

• World Wide Web is distributed, decentralized, hypermedia application.

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Representational State Transfer (REST) Style

User agent Origin ServerRequest

ResponseProxies Gateways

Intermediaries

C C C C

• A set of constraints based on WWW architectural style

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Process View of a REST-based Architecture

$ $Client+Cache:Client Connector: Server Connector: Server+Cache:

$ $

Origin Servers

User Agent

$$

DNS

$DNS

Proxy

Proxy Gateway

wais

http

orbhttp

http

http http

a

b

c

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Derivation of REST

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REST (cont.)

• Constraints– Client-server– Context-free (stateless)– Cache– Code on demand– Layered– Uniform Interface

• Benefits– Efficiency– Scalability– User perceived performance

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Commercial Internet-Scale Applications

• Google strategy– Simpler storage system offering fewer features– Data Storage and manipulation – A high fault-tolerant platform– Cost effective manner

• Google design– Google distributed file system (GFS)– MapReduce

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Google File System Architecture

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MapReduce

• Large-scale data processing• Map

– Take input key/value pair, generate a set of intermediate pair

• Reduce– Merge all intermediate values associated with the same intermediate key

Map (k1, v1) -> list(k2, v2)Reduce (k2, list(v2)) -> list(v2)

• E.g., word frequency– map (URL, contents) -> set of (word, 1) – Reduce (word, 1) -> set of (word, sum)

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MapReduce Execution Flow

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MapReduce (cont.)

• Architecture Provides– Automatic parallelization & distribution

– Fault tolerance• Walker failure• Master failure

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Decentralized Architecture

• Networked applications where there are multiple authorities

• Not a new idea– E.g., web sites, international postal mail

• Designing challenges

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Grid Computing

• Coordinated resource sharing and computation in a decentralized environment

• Technologies that allow consumers to obtain computing power on demand

• Starts with large-scale federated resources

• Issues – Interoperability– Security

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Grid Architecture

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Globus Grid Architecture (recovered)

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Cloud Computing

• A key computing platform for sharing resources• A specialized distributed computing paradigm

– Massively scalable– Different level of service– Driven by economies of scale– Dynamically configured and delivered on demand

• What makes Cloud Computing interesting now?• Not a new concept!

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Cloud Computing

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Three level Services by Cloud Computing

• Infrastructure as a Service(IaaS) – Amazon EC2

• Platform as a Service (PaaS) – Google App Engine

• Software as a Service (Saas) – Salesforce

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Grid vs Cloud Computing Grid Computing Cloud Computing

General 10 years agoLarge -scale federated systems

Now, new needs to analyze massive dataCommercial large-scale systems

The cost of computing Reliability & Flexibility with same issues

Business Model Pay for units spent Pay on a consumption basis

Architecture 5 layered 4 layered, 3 level services

Compute Model Batch-scheduled queuing system

Shared by all users at the same time

Data Model Virtual Data Triangle model

Security Strict Single sign-on

Simpler and less secureeasy to manage account

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Peer-to-Peer: LL

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Napster

•Hybrid client-server/P2P

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Gnutella

•Pure decentralized P2P

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Skype

•Overlayed P2P

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Review

• Distributed Network-based Applications- REST

- Google: GFS, MapReduce

• Decentralized Architecture- Grid Computing- Cloud Computing- Peer-2-Peer: Napster, Grutella, Skype

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References

• Principled Design of The Modern Web Architecture.– Fielding, Roy T., and Richard N. Taylor.

• Cloud Computing and Grid Computing 360-Degree Compared.– Foster, Ian, and Zhao Yong.

• MapReduce: Simplied Data Processing on Large Clusters– Dean, Jeffrey, and Sanjay Ghemawat.

• The Google File System.– Ghemawat, Sanjay, Howard Gobioff, and Shun-Tak Leung