CSE 190: Internet E-Commerce

1
CSE 190 Internet E-Commerce

• Lecture 14 Operations

2
Operations

• Everything it takes to keep a web site up and
  running, 24x7
• Deployment Process
• Monitoring (SNMP)
• Build system
• Link rot
• Maintenance window
• Load testing
• Browser compliance
• Log rotation
• Database backups
• Disk failure
• Router failure
• Robots
• Staffing
• Data centers
• Expense of running a high availability site is
  comparable to running a physical store front

3
Deployment Process

• Proceeds in three phases
• Development
• Within corporation, not accessible outside
• Stage
• Within internet environment
• UAT run here
• Only operations staff may access
• Live
• Accessible to outside world

4
Monitoring

• SNMP (Simple Network Management Protocol)
• Used to monitor both hardware, software
• Provides Counters, Values, Triggers, Statistics
• Remote control of services
• Information stored in MIB (Management Information
  Base)
• RMON sometimes used as alternative to SNMPv2
• Software
• HP OpenView

5
Maintenance Window

• Installation
• Standard J2EE standard web service descriptor
  (XML file with tarball of files)
• InstallShield
• Custom installation scripts
• Upgrades
• Defined time on Friday or weekend to upgrade
  site, posted on web site
• Process
• Front page linked to Site down
• Load balancer redirected if appropriate
• Application stops accepting new clients
• (Pause) Application terminates all active
  sessions
• Application upgraded
• Sanity checks performed
• Servers rebooted
• Load balancer restored

6
Link Rot

• Link rot the continual process by which links
  become invalid over time
• Tracked with custom tools
• Best practice Pages have permanent URLs
• Referral field
• Tracking this in logs shows whos linking to what
  URL on your site

7
Load Testing

• Network load (60 bandwidth max)
• Average page size (20-30k)
• CPU load Occurs at least three levels
• HTTP level
• Application level
• DB query level
• Metrics maximum number of simultaneous users,
  latency vs. users
• Memory usage (256 M 1 G per machine)
• Disk I/O load
• 1 Gb per machine typical
• Tools
• Mercury Interactive WinRunner
• Segue SilkTest
• Rational SiteLoad
• Microsoft WCAT

8
Browser Compatibility

• Cost of testing proportional to the number of
  platforms youre compatible with
• The same product isnt the same on different
  operating systems
• E.g. IE4.5 isnt the same on Mac vs. Windows
• Incompatible DOMs between MS, Netscape, Mozilla
• Browser archive
• http//browsers.evolt.org/

9
Robots

• Robots Automatically traverse web pages to
  retrieve documents, link structure, data
• Used for
• Indexing
• HTML validation
• Link validation
• Mirroring
• Problems
• Too much rapid access from single IP
• May be indexing dynamic, obsolete data
• Robot exclusion file /robots.txt file for
  mysite.com User-agent webcrawlerDisallow
  User-agent lycra Disallow / User-agent
• Disallow /jspDisallow /logs

10
Failure Models

• Mean Time To Failure (MTTF) average amount of
  time the system is up
• Mean Time between Failures (MTBF) average
  amount of time between failures
• Mean Time To Repair (MTTR) average amount of
  time the system is down after it fails - active
  repair time (diagnostics and repair)
• Mean Down Time (MDT) - average amount of time
  system is down after it fails - active repair
  time preventive maintenance logistics time
  (time spent waiting for personnel, etc)
• Intrinsic availability Mean Time To Failure
  (MTTF) Mean Time To
  Failure (MTTF) MTTR
• Operational availability Mean Time Between
  Failure (MTBF)
  Mean Time Between Failure (MTBF) MDT

11
When things go wrong

• Network operations
• Software recovers from common failures
• Network staff paged by email if server not
  available (via SNMP)
• Usually rotating assignment
• Application developers may be called in if
  restarting servers, etc. fails completely. Only
  if it doesnt look like a network problem.

12
Data Centers

• Data centers Host your machines in their own
  premises
• Also called colocation
• Features
• Security controlled entrance, exit
• Weather maintained temperature, humidity
• Power Backup power, available circuits
• Bandwidth OC-192 connections
• Monitoring 24/7 staff, may reboot misbehaving
  machines
• Machines typically arranged in cages 1u, 2u
  machines
• Server blades
• Examples
• NTT / Verio
• Exodus / Global Crossing