“load testing early and often” by donald doane presentation to the rockville mdcfug
TRANSCRIPT
“Load Testing Early and Often”
By Donald Doane
Presentation to theRockville MDCFUG
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Session Overview
OpenDemand Systems
• Introduction to Load Testing Web Applications
• Testing from Development to Deployment
• Load Testing Over the LAN vs. the Internet
• Creating a Real-World Example in ColdFusion
• Load Testing Best Practices
• Identifying Common Performance Bottlenecks
• ColdFusion Performance Tuning Hints and Tips
• Questions & Answers
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The ColdFacts
OpenDemand Systems
• Most developers are familiar with the “concept”
of load testing, but very few actually do it!
• Most common reasons for not testing are Time,
Complexity & Cost ($$$ can be very expensive)
• Most sites run into performance problems with
only a few users (you don’t have to be Victoria’s
Secret)
• Most performance problems are discovered too
late in the game to properly address the issues
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What is a Load Test?
OpenDemand Systems
• Simulates multiple users to measure, define, validate and maintain optimal application performance, scalability and reliability
• Serves as a compass for understanding the limits of any Web-enabled application and, subsequently, for managing its performance and growth
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Why Load Test from Development to Deployment?
OpenDemand Systems
Identifies problems early on before they become costly to resolve (avoid the pyramid effect) Prevents the “Onion-Peel” syndrome Reduces development cycles Produces better quality, more scalable code Prevents revenue and credibility loss due to poor Web site performance Increases customer satisfaction and retention Enables intelligent planning for future expansion
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What does it mean for your site to perform or scale well?
OpenDemand Systems
• Delivers page views to users in 8 seconds or less (industry standard)• Performs consistently across multiple page view requests (avoid the wack-o-mole effect)• Response times scale linearly as user load increases as opposed to exponentially
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Virtual User Simulation
OpenDemand Systems
• One-to-many relationship between user and browser requests• Browser opens multiple concurrent connections to Web server• HTTP Request-Response Thread:
GET / HTTP/1.1Host: www.mysite.com-------------------------------HTTP/1.1 200 OKContent-Length: 327Content-type: text/html
[BODY]
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OpenDemand Systems
Your Browser
Your Web Site/App
VirtualUsers
VirtualUsers
OpenLoad Appliance
Virtual Users
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Load Testing over the LAN vs. the Internet
OpenDemand Systems
LAN Testing: Eliminates network variability due to the Internet Saturates system rather than the network
Internet Testing: Uncovers hidden delays due to Internet weather Exercises your pipe, routers, firewalls and load balancers in addition to the system under test Ensures Service Providers are meeting SLAs
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Load Testing Do’s
OpenDemand Systems
Do test early and do test often Do establish what is and is not acceptable performance for your application Do test from the user’s perspective - it’s the only one that counts Do baseline and compare your findings Do monitor your system while you test Do test whenever there’s a change in your site’s content, code or infrastructure
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Load Testing Don’ts
OpenDemand Systems
Don’t wait until the last minute to test Don’t depend on your customers to do your testing for you Don’t test under unrealistic conditions Don’t forget that increases in table sizes, disk usage and network traffic will degrade your application’s performance over time Don’t be so quick to throw hardware at the problems you turn up - it doesn’t always help
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Creating a Real-World Example in ColdFusion
OpenDemand Systems
Customer Case Study: Set up a User Profile Configure a Load Test Scenario Schedule a Load Test Analyze Test Results
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Identifying Common Performance Bottlenecks
OpenDemand Systems
Over design of Web pages (too many graphics) Bad code (avoid recursive function calls) Web server connection limit too low (IIS is set to 10 by default) Poorly tuned Web application server (play with your Administration Server Settings) Excessive queue lengths (more than one) & wait times (more than a few milliseconds) Memory contention issues (paging in) Heavy disk I/O (high service times) Network latency (packet collisions & lost)
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Performance Tuning Hints & Tips
OpenDemand Systems
Observe design & coding best practices (Fusebox) Pre-load images before they are needed Validate on the client whenever possible (JavaScript or ActionScript) Strip formatting white space, tabs, carriage returns and line feeds from HTML (speeds up response) Upgrade to CF5 (Up to 5x faster than CF4.5) Tune simultaneous requests per CPU (cfstat) Turn on “Trusted Cache” & increase cache size Restart server at 5-10 unresponsive requests
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Performance Tuning Hints & Tips Cont’d
OpenDemand Systems
Log slow pages (remember 8-second rule) Enable Debugging (check processing time) Replace frequently referenced Custom Tags with User Defined Functions (less overhead) Bump up your cached query limit (if you can spare the memory) Let ColdFusion work smarter and your Database work harder (write smart SQL - don’t do SELECT *) Use stored procedures for faster execution
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Test your app for FREE
OpenDemand Systems
Register at http://www.opendemand.com/cf/ Test for up to 5 virtual users for FREE!
Try-out performance tuning tips
Test again and compare results to your baseline
