Load Sharing and Balancing

1
Load Sharing and Balancing

• - Saravanan Mathialagan
• Masters in Computer Science
• Georgia State University

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Agenda

• Introduction
• Basic concepts
• Advanced concepts of server Load Balancing
• Application - Global server load balancing (GSLB)
• Application Web Caching
• Load balancing in Java

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Introduction

• In computer networking, load balancing is a
  technique to distributed work between many
  computers, processes, hard disks or other
  resources in order to get optimal resource
  utilization and decrease computing time 3.
• The function is performed by the load balancers.

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Introduction Understanding the Load Balancer

• Fig 1.1 Server Farm with a load balancer 2

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Introduction Understanding the Load Balancer

• An easy example Router in a call center server
• Load Balancer Software hardware
• Various other functions like
• Server load balancing
• Firewall load balancing
• Transparent cache switching
• Server protection
• Fault Tolerance
• Load Balancer does not works in the application
  level

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Advanced Concepts

• Session Persistence
• The mega proxy problem
• Delayed binding
• Cookie switching

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Advanced Concepts - Session Persistence

• How application that runs on top of TCP/IP
  protocol affects the function of load balancer
  Maintain Session2

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Advanced Concepts the mega proxy problem

• Situations where the source IP is not a reliable
  way to identify a user, due to a proxy server is
  known as the megaproxy problem

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Advanced Concepts

• Delayed Binding
• Delayed binding is this process of delaying the
• binding of a TCP connection to a server until
• after the application request is received.
• Cookie Switching
• Reading the cookie information to solve the
• Mega proxy problem

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Application - Global Server Load Balancing

• Domain Naming Service
• Positioning the GSLB
• Not to affect the existing flow
• Site selection

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Application - GSLB

• Site selection based on the following 2
• Site health conditions
• Site response time
• Site Loading time

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Application Web Caching

• Caches can be installed and utilized with the
  Load balancers in the following ways 2
• Forward proxy for client acceleration
• Transparent proxy for client acceleration
• Reverse proxy for server acceleration
• Transparent reverse proxy for server acceleration

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Application Web Caching

• Transparent reverse proxy for server acceleration
  2

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Load Balancing in Java

• Load Balancing for Servlets and JSPs
• Load Balancing for EJBs and RMI Objects
• Load Balancing for JDBC Connections

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Load balancing in Java Servlets and JSPs

• Load Balancing with a Proxy Plug-in
• Weblogic proxy plug-in maintains as list of web
  logic servlet and JSP instances
• Forwards the HTTP request to those cached
  instances in round-robin method
• Some webservers and associated proxies
• Weblogic server HTTPClusterServlet
• Apache with Apache proxy plug-ins
• Microsoft IIS with IIS plugins

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Load balancing in Java EJBs and RMIs

• The Object instances stored in the stubs 1
• Techniques
• Round Robin Load Balancing
• Weight-Based Load Balancing
• Random Load Balancing

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Load balancing in Java EJBs and RMIs

• Round Robin Load Balancing
• Server instances called in order
• Simple and cheap are the advantages
• If one is slow others will be affected
• Weight based load balancing
• Weighted in scale of 1-100 depending on the load
  managed by server
• Load distributed accordingly
• Random Load Balancing
• Does not discrete difference in processing and
  assumes homogenous systems
• Overhead in generating random number
• simple

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Load balancing in Java JDBC Connection

• Load balancing of JDBC connection requires the
  use of a multipool configured for load balancing.
  Load balancing support is an option you can
  choose when configuring a multipool 1.
• Multipool has an ordered lit of connection pool
  that routes the connection
• Default the first connection pool if not run in
  load balancing mode

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References

• Load Balancing in Java 1
• http//e-docs.bea.com/wls/docs81/cluster/
• load_balancing.html1043771
• Other references on load balancing from 2
• Load Balancing Servers,Firewalls, and Caches by
  Chandra Kopparapu
• Wiki Load Balancing 3
• http//en.wikipedia.org/wiki/Load_balancing