Using Global Server Load Balancing to Improve Web Site Performance

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Using Global Server Load Balancing to Improve Web
Site Performance

• Jeff Poe, NWS Office of Chief Information Officer
• Bruce Marshak, NWS Southern Region Headquarters
• NOAATech 2006
• November 3, 2005

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GSLB in NWS Web Farms

• Agenda
• Problem Overview
• Global Server Load Balancing (GSLB)
• Summary
• Future Plans

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GSLB in NWS Web Farms

• Problem Overview
• NWS currently has six web farms providing Web
  Services (OCIO, NOAA, SRH, ERH, CRH, WRH)
• Different circuit capacities from OC-12 to T3
• Publics response to certain severe weather
  events could use all available circuit capacity
  at a web farm
• Hurricane landfall for SR
• Severe thunderstorm activity in CR or ER

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GSLB in NWS Web Farms

• National Doppler Radar Sites

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GSLB in NWS Web Farms

• Maximum Bandwidth per day in Mbits/sec for 2004

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GSLB in NWS Web Farms

• Problem Summary
• Web farm bandwidth requirement had doubled each
  year for the past 3 years
• Web farms did not have capacity to serve
  projected increase for 2005
• Strategies to handle increased usage
• Bigger Faster Circuits
• Content Delivery Network a.k.a. Web Caching
  Service
• Akamai
• Mirror Image Internet
• Global Server Load Balancing

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GSLB in NWS Web Farms

• GSLB Overview
• GSLB acts as a DNS proxy for selected domain
  names
• Local server load balancer (SLB) serving requests
  to web servers at the web farm for a virtual IP
  address
• Multiple virtual IP addresses and multiple domain
  names
• Uses algorithm consisting of several configurable
  policies and metrics in order to select best web
  farm for a user
• Automatically redirects users away from failed
  sites
• Conceptually aggregates servers and circuit
  capacity allowing more efficient use of resources
• Need content mirrored at globally load balanced
  server farms

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GSLB in NWS Web Farms

• Domain Name Service (DNS) Operation
• User requests URL, browser queries local DNS to
  resolve hostname to IP address
• Local DNS performs queries iteratively,
  ultimately reaching the authoritative DNS for
  requested domain name
• Authoritative DNS replies with one or more IP
  addresses for a given domain name
• Local DNS responds back to users browser, which
  opens TCP connection to given IP address and
  downloads web pages
• Local DNS caches authoritative DNS response and
  provides same address for future requests to
  domain until time-to-live (TTL) parameter of
  domains IP specified by authoritative DNS
  expires

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GSLB in NWS Web Farms

• Drawbacks of DNS
• Web server farm supporting website is down or at
  capacity limit, authoritative DNS continues to
  return that web farms IP address in response to
  local DNS queries until authoritative DNS is
  manually updated
• If application that serves that website is down,
  users receive error code, timeout, or stale data

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GSLB in NWS Web Farms

• DNS with GSLB
• User requests URL, browser queries local DNS to
  resolve hostname to IP address
• Local DNS performs queries iteratively,
  ultimately reaching the GSLB as the authoritative
  DNS for requested domain name
• GSLB uses algorithm to select best Virtual IP
  (VIP) address for a given domain name and
  responds to local DNS
• Local DNS responds back to users browser, which
  opens TCP connection to given VIP address and
  downloads web pages
• Local DNS caches authoritative DNS response and
  provides same address for future requests to
  domain until time-to-live (TTL) parameter of
  domains IP specified by authoritative DNS
  expires

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GSLB in NWS Web Farms

• GSLB Policy / Metric processing order
• Server health check
• Weight of VIP
• Remote SI's session capacity threshold
• Round trip time between remote SI and client
• Geographic location
• Remote SI's available session capacity
• Remote SI's preference value
• Least response selection

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GSLB in NWS Web Farms

• Milestones
• Feb 05 Foundry Training
• Mar 05 Installation and Configuration
• Apr 05 May 05 Testing and Proof of Concept
• May 05 Serving live data
• May 05 Jun 05 Phased Implementation into
  Production
• Jul 05 Dennis, Emily
• Aug 05 Irene, Katrina
• Sep 05 Ophelia, Rita
• Oct 05 Stan, Wilma

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GSLB in NWS Web Farms

• Summary
• gt 100 increase in peak traffic with ample
  available headroom in bandwidth and server
  capacity
• Average response times lt 1 sec
• Improved availability, reliability, and provided
  a better service to the public
• Able to take a web farm out of production for
  maintenance without impacting users

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GSLB in NWS Web Farms

• Future Plans
• Additional domains and services
• NOAA web farms
• Norman and Boulder

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GSLB in NWS Web Farms

• Project Team
• Susan Beckwith SRH
• Bill Gery CRH
• Alex Hsia NOAA Boulder
• Chi Kang NOAA Silver Spring
• Paul Kirkwood SRH
• Bruce Marshak SRH
• Todd Metcalf ERH
• Reginald Pace NOAA Silver Spring
• Sameka Prather NWS OCIO
• Graham Stork - WRH
• Joe Rizo Foundry
• Fortune Vilcko ERH
• Eric Williams - NCIRT

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GSLB in NWS Web Farms

• Thank You!