Error and Access Logging Overview

The web server can generate two kinds of log file, the access log and the error log. The access log is controlled on a per Virtual Server basis by the log module. When enabled, the access log records information about every transaction the web server has processed. This can be in a standard format, such as Common Log Format (CLF), or a user-specified format for maximum flexibility.

The error log file (which by default lives in $ZEUSHOME/web/log/errors) records notable events in the web server which are not able to be logged in the transaction format of the log file. For example, events such as starting or stopping a Virtual Server, running out of file-descriptors or Virtual Server startup configuration errors.

An error log line is categorized into one of 4 levels of increasing severity, 'INFO', 'WARN', 'SERIOUS' and 'FATAL'. A sample log line is shown here:

[18/Apr/2000:10:49:31 +0100] INFO:Zeus Web Server started

Errors pertaining to a particular Virtual Server have the Virtual Server name postfixed to the severity level. For example, if the Virtual Server was called 'main', a sample log line could be:

[18/Apr/2000:10:49:31 +0100] INFO:main:Website http://www.mysite.com starting

It is possible to configure Virtual Server specific entries to log to a separate log file on a per-Virtual Server basis instead of logging them to the main log. This is achieved on the 'General Configuration' section for that Virtual Server.

As well as messages generated by the web server, the error log file is used to capture output from the standard error ('stderr') channel of CGI scripts. This output contains the error messages generated by CGI scripts and will not be in the above format. This information is useful in debugging CGI scripts. Alternatively, it is possible to configure the web server to send the 'stderr' output for the CGI script to the client's browser instead of logging it to the error log file, by changing the tunable "tuning!modules!cgi!logstderr" to "yes".

List of run-time and startup error/warning messages

Detailed in the appendix, are a list of the most common run-time and startup error and warning messages.