research heaven, west virginia pi: katerina goseva – popstojanova students: ajay deep singh &...
DESCRIPTION
Research Heaven, West Virginia 3 Relevance to NASA Increasing use of Web-based technology at NASA Web sites Agency wide Control of daily mission operations from multiple geographically distributed locations via Internet (e.g., Web Interface for Telescience at JPL) Real-time applications remotely controlled/monitored over the Internet or an Intranet (e.g., Tempest embedded Web server at Glenn Research Center)TRANSCRIPT
Research Heaven,West Virginia
PI: Katerina Goseva – PopstojanovaStudents: Ajay Deep Singh & Sunil Mazimdar
Lane Dept. Computer Science and Electrical Engineering West Virginia University, Morgantown, WV
Performability of Web-based Applications
2
Research Heaven,West Virginia
Problem
• World Wide Web is the biggest existing distributed system so far – Huge number of Web clients - tens of millions and rising– Users demand 24/7 availability and response time within
several seconds – However, very often they experience long and unpredictable
delays
(WWW - World Wide Wait)
• Problem: Traditional analysis and prediction methods do not work for Web
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Research Heaven,West Virginia
Relevance to NASA
Increasing use of Web-based technology at NASA• Web sites Agency wide
• Control of daily mission operations from multiple geographically distributed locations via Internet (e.g., Web Interface for Telescience at JPL)
• Real-time applications remotely controlled/monitored over the Internet or an Intranet (e.g., Tempest embedded Web server at Glenn Research Center)
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Research Heaven,West Virginia
Relevance to NASA • Our empirical analysis is based on data extracted from
actual Web logs of ten servers– Three public and three private Web servers at the NASA IV&V Facility– Lane Department of Computer Science and Electrical Engineering
(CSEE) Web server– NASA Kennedy Space Center (NASA-KSC) Web server
– Campus wide Web server at the University of Saskatchewan– Web server of the commercial Internet provider ClarkNet
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Research Heaven,West Virginia
Approach
Develop methods and tools that are general and powerful enough to provide flexible analysis and quality assurance of Web reliability, availability, and performance
Develop scalable framework that combines measurements and models at different levels of detail and abstraction
• Reliability/Availability: based on typical usage patterns• Performance: non-Poisson queuing theory• Combine reliability / availability and performance and analyze their
tradeoffs
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Research Heaven,West Virginia
Approach
Web access log analysis
User session characterization
Realistic workload
Software/hardwareresource utilization
Application & hardware resource
monitoring
Web error log analysis
Request-based and session-based error
characterization
Software/hardwarefailure/recovery
characterization
Performabilitymodel
Session layer
(user view)
Service layer(software
architectural view)
System layer(deployment view)
Reliability/availability
model
Performancemodel
Resource layer(hardware device
view)
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Research Heaven,West Virginia
Accomplishments
Workload analysis
Intra-sessioncharacteristics
Inter-sessioncharacteristics
Web log files
Create relational database
Errors and reliabilityanalysis
Unique errors(frequency &
severity)
Request-basedreliability
Session-basedreliability
Unique fileswith errors
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Research Heaven,West Virginia
Accomplishments
• Empirical analysis of the Web workload, errors, request-based and session-based reliability for ten Web servers
1 2 3 4 5
6-10
11- 2
0
21- 5
0
51- 1
00
101-
250
251-
700
701-
150
0
1501
- 300
0
3001
- 500
0
CS
EE
1
CS
EE
2
1
10
100
1,000
10,000
100,000
Num
ber o
f uni
que
erro
rs
Frequency of occurrence
Error rates have heavy tail distributions
0
5
10
15
20
25
30
35
% E
rror
sNASAPvt1
NASAPvt2
NASAPvt3
NASAPub1
NASAPub2
NASAPub3
CSEE 1 CSEE 2
File 3
File 2
File 1
10-35% of the total number of errors are due only to 3 files
• Some examples
• Fixing the errors with the highest frequency of occurrence is the most cost effective way to improve Web quality
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Research Heaven,West Virginia
Accomplishments
0 1 2 3 4 5 67
89
10 >10NASA-Pvt 1
NASA-Pvt 2
NASA-Pvt 3
NASA-Pub 1
NASA-Pub 2
NASA-Pub 3
CSEE
ClarkNet
NASA-KSC
Saskatchewan
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
% s
essi
ons
Number of errors per session
We argue that session-based reliability is a better indicator of the users perception of the Web quality than request-based reliability
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Research Heaven,West Virginia
Importance/benefits
• Innovative theoretical and empirical research results– Introduced and empirically analyzed new measures for
session-based workload and reliability– Conducted detailed empirical study on Web errors,
including severity level of errors, unique errors, and unique files with errors – measures that have not been considered earlier
• Practical value – The results of our research were actually used by Web
administrators of the NASA IV&V and CSEE Web servers to improve their quality in a cost-effective way
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Research Heaven,West Virginia
Next steps
• Performance attributes – Develop non-Poisson queuing theory
• Standard performance models (Queuing Networks & Layered Queuing Networks) assume Poisson arrivals
• Web workload is bursty (highly non-Poisson)
• Dependability attributes (reliability, availability)– Develop architecture-based models based on typical usage patterns
• Combine performance and reliability / availability models– Analyze tradeoffs among multiple quality attributes