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Resolving Web Services Performance Challenges

Understand the dynamics of web services performance, address common problems, and monitor metrics for optimal delivery. Learn about QoS indicators and essential measurements to enhance user experience and system efficiency.

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Resolving Web Services Performance Challenges

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  1. CS6320 – Web Services and Performance L. Grewe

  2. Web Services • Services available via the Internet that complete tasks or conduct transactions. • Self-contained, modular applications that can be described, published, and invoked over the Internet. • Can be automatically invoked by application programs.

  3. Web Services • May be invoked at one site or may combine results of several services executed at different sites.

  4. Performance concerns differ from standard Client/Server • May involve both web service processing and network delays • May be accessed by wide variety of devices -- desktop computers, PDAs, mobile phones, other servers • Access via wireless communication networks: dynamic connectivity, low bandwidth, high latency

  5. Performance concerns differ from standard client/server • Undpredictable nature of requests • Highly bursty • Varies with geographical location of clients, day of week, time of day • Highly variable size of requested objects • “Robot” access • Autonomous software agents that can consume significant amounts of system resources

  6. Types of servers providing Web Services • Web servers • Transaction servers • Proxy servers • Cache servers • Wireless gateway servers • Mirror servers

  7. Common problems • Insufficient bandwidth at peak times • Overloaded servers • Uneven server loads • Delivery of dynamic content • Shortage of connections between application servers and database servers • Failure of third-party servers • Delivery of multi-media content

  8. Example:Bill Paying Service • Portal offers bill paying service • Customers can pay variety of bills through the service • Uses services provided by others: • Debit authorization (100 tps capability) • Electronic funds transfer • Customer authentication

  9. Example:Bill Paying Service

  10. Example: Bill Paying Service • Portal B is bill paying service • Treat overall web service as ‘system’ • Treat component services as ‘devices’ • What is the capacity of B, given that the debit authorization service can support 100 tps and that each payment transaction requires 2 visits to the authorization service …..answer 50tps. (this assumes that the authentication is the slowest device).

  11. Review – web service can return many kinds of Web (HTTP) content

  12. Perception of Performance • User view: • Fast response time; no connections refused • Management view: • High throughput; high availability • Need to have quantitative measurements that describe behavior of Web service

  13. Metrics • Two most important; • Response time -- seconds • Throughput -- http_ops/sec, also bits/sec

  14. Other metrics • Hit • any connection to a web site, including in-line requests and errors • difficult to compare across sites • Visit • Series of page requests by a user at a single site • Inter-request times < timeout_value • Session • Series of consecutive and related requests made during a single visit • Inter-request times < timeout_value

  15. Other metrics • User-perceived response time • Set of geographically distributed agents poll the WS • Error rate • Increase indicates degrading performance • Examples: • Overflow of pending connection queue • For streaming services: • Jitter • Startup latency

  16. Most common measurements of Web service performance • End-to-end response time • Site response time • Throughput (req/sec or transactions/sec) • Throughput (Mbps) • Errors/sec • Visitors/day • Unique visitors/day

  17. Example - Travel Agency • Monitor for 30 minutes: • 9000 HTTP requests • Three types of objects delivered: • Html pages (30%, avg. size 11,200 bytes) • Images (65%, avg. size 17,200 bytes) • Video clips (5%, avg. size 439,000 bytes) • What is the throughput: • 9000 requests/1800 sec = 5 req/sec • What is the throughput in Kbps?

  18. Throughput in Kbps? • Xr = (total_req * class% * avg. size)/time • Xhtml = (9000 * 0.30 * 11,200*8)/1800 = 131.25 • Ximage = (9000 * 0.65 * 17,200*8)/1800 = 436.72 • Xvideo = (9000 * 0.05 * 439,000*8)/1800 = 857.42 • X0 = 131.25 + 436.72 + 857.42 • X0 = 1425.39 Kbps To support the Web traffic, the network connection should be at least a T1 line (1.544 Mbit/s ).

  19. QoS indicators for Web Services • Response time • Availability • Percentage of time a service is ‘live’ (serving customer requests) • Reliability • Probability that WS will perform in satisfactory manner for a given period of time under specified operating and load conditions • Predictability • Cost

  20. Input data needed to monitor QoS • Traffic • Performance • Usage patterns • Knowledge of average and peak load

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