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Web Load Balancing Through More Accurate Sever Report

Web Load Balancing Through More Accurate Sever Report. C. Edward Chow and Indira Semwal Department of Computer Science University of Colorado Springs In the 2 nd PDCAT conference. Outline. 1. Introduction 2. Related Research 3. Apache Web Server with Accurate Server Load Reporting

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Web Load Balancing Through More Accurate Sever Report

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  1. Web Load Balancing Through More Accurate Sever Report C. Edward Chow and Indira Semwal Department of Computer Science University of Colorado Springs In the 2nd PDCAT conference

  2. Outline • 1. Introduction • 2. Related Research • 3. Apache Web Server with Accurate Server Load Reporting • 4. Webstone Benchmarking Result • 5. Conclusion

  3. 1. Introduction • How to spread work load? --Replication --Cluster systems, web switch, and control devices.

  4. Introduction(cont.)

  5. Introduction(cont.) • To determine “ better” replicated servers -- Geographic proximity -- Factors that affect the quality of connection or response time of a remote server. • LBA( Load Balancing Agent) --The bottleneck bandwidth -- The available bandwidth -- The expected delay at the web server. How to probe the network??? Bprob and Cprob. The delay at the server is measured by the server itself.

  6. Introduction(cont.) • Modified balancing DNS server

  7. 2. Related Research • In the past: --Geographical location --Some dynamic algorithm • Round-Robin scheme • Clients must have knowledge about the traffic on the path

  8. 3. Apache Web Server with Accurate Server Load Reporting • The Apache provides a server status about the history of: -- CPU load -- server throughput -- connection rate -- The pending queue size of requests

  9. Each child process keeps: -- byte remaining= file size – bytes already transferred -- Total access= the sum of requests made to all the children(count) -- Total traffic= the sum of bytes served by each child(kbcount) -- Bytes served -- Bytes/ sec= kbcount/ uptime -- Bytes per request= kbcount / count -- CPU load -- Request/ sec= count/uptime

  10. Statue handler Child Speed=( the sum of Bytes sent/ the sum of time)/ N Average Speed= the sum of child speed / The number of alive children precesses Time left= B/ Average Speed

  11. LBA (Load Balance Agent) -- Network bandwidth for each replicated web server -- Network Congestion bandwidth -- Expected delay at the server

  12. About the report of probing result -- Write the output to a file and then parse it. -- Use sockets to send the final bandwidth information to the LBA. -- Write out the final bandwidth and host name to a file, apart doing a screen dump  Weight = (1+b_result+c_result)/((1+delay)*10000)

  13. 4. Webstone Benchmarking Result • Hardware configuration for Web server 4 Pentium 500 MHz PCs(128 M) LAN: 100 Mbps Web server; Apache 1.3.9 • Hardware configuration for LBA 1 Pentium 240 MHz PC (128 M) O.S: Redhat 7.0

  14. 5. Conclusion • The better performance is near the 5-second update interval and the the connection rate is better than round-robin scheme near 1.9 times. • In the future -- few LBAs to serve in the WAN -- LBA s could exchange information to each other (multicast) -- Bprobe is very slow  SimProbe

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