Web Server System - Network Processing Architectures - Lecture Slides, Slides of Computer Architecture and Organization

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Implementing a Load-

balanced Web Server System

Architecture of A Cluster-based Web System

Courtesy: IBM Research Report, The state of the art in the locally distributed Web Server systems. Docsity.com

Our Web Server Cluster

• The whole web server only provides one

visible web address to the outside world.

• Each Web Server is able to provide two

kinds of web services.

• The load distributor distributes the

incoming requests among the servers

according to either content-aware or

content-unaware load balancing

strategies. Docsity.com

Tasks to do to set up the

system

• Building up the web services on the

servers

• File Services
• Video-on-demand Services
• Database Services

• Implementing the load distributor on the

frond-end node

• Content aware request distribution
• Content unaware request distribution Docsity.com

Video On Demand Service

• VideoLAN project (Open Source Media Streaming

Solution)

• Targeting multimedia streaming of MPEG-1 , MPEG-2 , MPEG-4 and DivX files, DVDs , digital satellite channels, digital terrestial television channels and live videos on a high-bandwidth IPv4 or IPv6 network in unicast or multicast.
• Client-server Architecture
• Server streams MPEG-1, MPEG-2 and MPEG-4 / DivX files, DVDs and live videos on the network in unicast or multicast.
• Client receives, decodes and displays MPEG stream.

VideoLan System

Load Balancing Schemes

• Content Unaware Scheme

• Choose a server before receiving the URL

request

• Round Robin

• Content Aware Schemes

• Choose a server to dispatch a request after

receiving and looking at the URL request

• Balance load according to different URL

request

• For database service — Database Server Docsity.com

Implementing the Load

• Install the TCPSPDistributor

• The tcp splicing is a technique to splice two connections inside the kernel, so that data relaying between the two connections can be run at near router speeds.
• Write the Distributor program in C language
• Two load balancing strategies are implemented
• The installed kernel module TCPSP is invoked to perform TCP splicing
• Run the distributor program in the application level

Flow Chart of the Load Distributor (content unaware)

Establish a TCP connection with the chosen server Listen for incoming connections on port 8888

Accept the connection

Choose a server according to the load balancing scheme

Create a child process to do further processing

End

Splice two TCP connections

Read the URL request

Write the URL request to the second TCP connection

Monitor the two TCP connections and close them when no more activities are going on

Distributor Child P rocess

Comparison with Gage

• Gage : A QoS Aware Web Server

System

• “Performance Guarantees for Cluster-Based

Internet Services”, Chang Li, State

University of New York at Stony Brook.

• The load distributor is implemented as a

kernel module. It is faster but can only

implement content-unaware load

balancing.

• SPECWEB

Let’s go to the lab to see

DEMO!