HTTP Access Logging

To monitor who is using your server, set up HTTP access logging in Tomcat. Every request that comes to Tomcat gets an entry in the access log.

Setting up Logging

To setup access logging, edit the Tomcat server configuration file, ${tomcat_home}/conf/server.xml and uncomment the AccessLogValve:

        <Valve className="org.apache.catalina.valves.AccessLogValve"
directory="logs" prefix="localhost_access_log." suffix=".txt"
pattern="common" />

By default the log files are created in the ${tomcat_home}/logs directory and roll over to a new file at midnight.

The log messages can be written in either of two standard web access log formats by setting the pattern attribute to common or combined. These appear to be the ones used by web log analysers. Other log formats can be specified with the pattern attribute.

More information on the AccessLogValve and the pattern attribute can be found on the Tomcat Valve Configuration Reference.

Modifying the Log Format

We can extend the "common" and "combined" patterns by appending the response time for each request. To use this, set the


Using FastCommonAccessLogValve

The FastCommonAccessLogValve has better performance than the AccessLogValve. If you are running a production system, you might consider switching to the FastCommonAccessLogValve. The main restriction is that only the "common" and "combined" log formats can be used.

        <Valve className="org.apache.catalina.valves.FastCommonAccessLogValve"
directory="logs" prefix="localhost_access_log." suffix=".txt"
pattern="common" />

The Logging Output

Here is a sample entry from the motherlode logs, using the combined plus response time pattern.

Example log entry: - joe [01/Jul/2007:08:44:38 -0600] "GET /thredds/dodsC/fmrc/NCEP/GFS/Global_0p5deg/offset/NCEP-GFS-Global_0p5deg_Offset_0.0 HTTP/1.1" 200 32707 "null" "IDV/NetcdfJava/HttpClient" 2999
Example Value Meaning client IP address
- not used
joe authenticated username
[01/Jul/2007:08:44:38 -0600] request time
"GET ..." HTTP request verb and path
200 HTTP response code
32707 bytes transferred
"null" Referer
"IDV/NetcdfJava/HttpClient" client name
2999 response time in msecs


Using Web Log Analysers

We have used these two Web Log Analysers, but there are many others to choose from.

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