Information Technology Reference
In-Depth Information
T
ABLE
I
G
ENERIC
E
RROR
T
YPES AND THE
R
ECORDED
E
RRORS
BY
T
YPE FOR
SMU/SEAS
Type
Description
# of errors
A
permission denied
2079
B
no such file or directory
14
C
stale NFS file handle
4
D
client denied by server configuration
2
E
file does not exist
28
,
631
F
invalid method in request
0
G
invalid URL in request connection
1
H
mod_mime_magic
1
I
request failed
1
J
script not found or unable to start
27
K
connection reset by peer
0
All types
30
,
760
Type A errors, accounting for 6.8% of the total recorded errors, involve improper
access authorization or problems with the authentication process. These errors are
more closely related to security problems instead of reliability problems we focus on
in this chapter. Further analyses of them may involve the complicated authentication
process. In addition, type A errors also account for much less of a share of the total
recorded errors than type E errors. Therefore, we decided not to focus on these errors
in our study.
Type E errors usually represent bad links. They are by far the most common
type of problems in web usage, accounting for 93.1% of the total recorded er-
rors. This is in agreement with survey results from 1994-1998 by the Graph-
ics, Visualization, and Usability Center of Georgia Institute of Technology (see
http://www.gvu.gatech.edu/user_surveys
)
. The surveys found that broken link is the
problem most frequently cited by web users, next only to network speed problem.
Therefore, type E error is the most observed web content problem for the general
population of web users. Further analysis can be performed to examine the trend of
these failures, to guide web testing, and to provide an objective assessment of the
web software reliability.
For the KDE web site, only access logs are used but not the error logs. However,
from the HTTP response code, we can extract the general error information. For
example, type E (missing file) errors in the error logs are equivalent to access log
entries with a response code 404. The access logs for the KDE web site for the 31
days recorded more than 14 million hits, of which 793,665 resulted in errors. 785,211
hits resulted in response code 404 (file-not-found), which accounted for 98.9% of all
the errors. The next most reported error type was of response code 408, or “request
