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					Performance Assessments of
     Internet Systems

                  By
          Kishore G. Kamath
        SPAN Technologies
         Testing solutions for the enterprise
        www.spantechnologies.com
      Kishore@spantechnologies.com
              973-575-7235



         Copyright 2003 by SPAN Technologies.
Agenda

•   Why do Internet systems under perform?
•   Performance analysis in the corporate world
•   How do automated tools work?
•   Simulating user load
•   Assessing computer systems




               Copyright 2003 by SPAN Technologies.
Performance Considerations for
Internet Applications
            • Why do Internet applications under-perform?
               – Application Design/Implementation
                   » In-efficient database queries
                   » Poorly written code
            • Identification
               – Simulate light user-load
               – Measure system metrics on Database / App Server
                   » CPU Utilization, Disk I/O and Processor Queue
Web Users            Length



                                                                  Database
                                                                   Server
             Web Server
                                               App Server

                          Copyright 2003 by SPAN Technologies.
Performance Considerations for
Internet Applications




           Courtesy Mercury Interactive Corp


               Copyright 2003 by SPAN Technologies.
Performance Considerations for
Internet Applications
     • Why do Internet applications under-
       perform?
        – Unbalanced System Topology
            » Physical design and topology may be
              in-efficient                                                   Database
                                                                             server
            » App Server components may not be
              co-located on same box.                                 Web
                                                                      Server 2


     • Identification                                      Load
        – Simulate moderate user-load                      balancer

        – Measure system metrics on Database / App                               App
                                                                                 server
          Server
            » CPU Utilization, Disk I/O and
              Processor Queue Length
     • Measure network metrics
        – Characteristics
            » High network load
            » Moderate CPU Utilization
                   Copyright 2003 by SPAN Technologies.
Performance Considerations for
Internet Applications
      • Why do Internet applications under-perform?
         – In-adequate Server/Network Capacity
              » Server hardware under equipped to handle
                software demands.
              » Network pipe to the Internet is too small.

      • Identification
         – Simulate anticipated user-load
         – Measure system metrics on Database / App Server
             » CPU Utilization, Disk I/O and Processor Queue
               Length
         – Measure network metrics
         – Characteristics
             » High network load / High CPU Utilization, Disk I/O
               or Processor Queue Length.


                    Copyright 2003 by SPAN Technologies.
Performance Considerations for
Internet Applications




        Courtesy Mercury Interactive Corp

                 Copyright 2003 by SPAN Technologies.
Performance analysis in the corporate
world
     • Create a Test Region a scale of production
     • Simulate user activity using an automated performance tool
       (Mercury Interactive LoadRunner, Compuware QALoad, Empirix
       E-Load or Segue Silk Performer)
     • Use automated tools to
        – Record user activity
        – Replay user activity x number of users to simulate.

     • Examine system behavior under simulated load
        – Review system metrics
        – Do root-cause analysis.




                    Copyright 2003 by SPAN Technologies.
How do automated tools work?
                • How recording works
                        – Capture user activity at a protocol level
                        – Create a proxy server to capture HTTP requests from
                          a browser
                        – Capture HTTP request components including server
                          target requested and name value pairs.
                        – Store these HTTP requests into a script.

    Record                                         Web             App      Database
                                                                            server
                                                                   server
                                                   server
                        1
                            Private
               HTTP Request Proxy
                       Script
name = “jane”
password = “courant”




                                   Copyright 2003 by SPAN Technologies.
How do automated tools work?
             • How replay and analysis work
                    – Make HTTP requests stored in script.
                    – Replace pivotal values in name-value pairs with other
                      values.
                        » Prevent caching from making results optimistic.

                                               Replay
                                                                                  Database
name = “jane”                                                            App
                                                         Web                      server
                                                                         server
password = “courant”                                     server
                       Script
                                  HTTP Request
name = “john”
password =NYU”           Script

                                Script
 name = “harry”
 password = “edu”




                                     Copyright 2003 by SPAN Technologies.
How do automated tools work?
     • How replay and analysis work
        – Server cannot tell apart a script replay from a real-user
          request.
        – Multiple instances of script execution can simulate
          multiple users.
            » Instances can simulate increasing, decreasing,
               steady-state or random user load.
        – HTTP requests and server response and behavior
          metrics can be monitored and collated.
        – Correlations between requests and behavior can be
          analyzed.




                   Copyright 2003 by SPAN Technologies.
LoadRunner Installation: Review                                                                        6


Putting it all Together
                              Performance metrics




                    Web                  App              Database
                    servers              servers          server




                                                                                          Load Simulator
                                                                                          Machine 2
                                LR
                                CONTROLLER

                          1.Control desk.                                    LOAD
                                                                             GENERATOR 1
     LOAD                                                                         (SF)
     GENERATOR 2
        (NY)

 2.Load Simulator
 Machine 1                                                             3. Analysis Tool
                                                     LR
                               Copyright 2003 by SPAN Technologies.
                                                     ANALYSIS
Performance analysis
     • Light load
        – Load is less than 10% of expected load.
        – Review of transaction response times and
          server/network metrics
            » High response time coupled with high Disk I/O or
              CPU Utilization is indicative of bad code/queries.




                     Copyright 2003 by SPAN Technologies.
Performance analysis




         Courtesy Mercury Interactive Corp



                   Copyright 2003 by SPAN Technologies.
Performance analysis
        • Steady state 100% load
             – Review of server/network metrics
                 » Increasing trend indicates an issue
                 » Memory leaks can be determined




   Courtesy Mercury Interactive Corp
                            Copyright 2003 by SPAN Technologies.
Performance analysis
     • Capacity Planning
        – Increasing load past expected load levels
            » Review of response times and server/network
               metrics
                • Response time under expected and future
                   load.
                • Server/network utilization under expected
                   and future load




                                        Courtesy Mercury Interactive Corp




                   Copyright 2003 by SPAN Technologies.
   Performance analysis




Courtesy Mercury Interactive Corp




                                     Copyright 2003 by SPAN Technologies.
Comparative studies

      • Run load under 2 different conditions
         – Example
             » With and without SSL.
             » Two different server hardware configurations.
             » Two different configuration settings

      • Compare response times and metrics to study
        impact of change
         – Used for tuning, benchmarking.




                   Copyright 2003 by SPAN Technologies.
Courtesy Mercury Interactive Corp




                                     Copyright 2003 by SPAN Technologies.
IP based load-balancing

      • Load re-directors will send load from one IP address
        to the same web server.
      • Load simulation would need to use different IP
        addresses to simulate multiple users
      • Load simulator will spoof IP Addresses not in use
        when making requests to the server.
         – Max of 25-8192 IP addresses per Network card
           depending upon OS.
      • Load balancer uses IP address to direct load to
        appropriate web-server based on hashing algorithm
      • Server host alias file re-points IP addresses back to
        the true load simulator IP address.




                   Copyright 2003 by SPAN Technologies.
Summary

• Performance assessments of Internet systems
  are achieved via simulation.
• Automated tools can create realistic load by
  simulating HTTP requests while changing data.
• Correlation of system metrics with level of load
  can identify performance issues and their root
  cause.




           Copyright 2003 by SPAN Technologies.

				
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