To enable http level request/response logs in Application Server (AS), we can use the Access_Log_Valve which is provided in Tomcat 7.
To enable logging, you have to put the following XML element under the /Server/Service/Engine/Host/ directory in the {WSO2AS_HOME}/repository/conf/tomcat/catalina-server.xml file and restart the AS server.
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_sample."
suffix=".log"
pattern="%{xxx}i %{xxx}o"
resolveHosts="false"/>
This will create a log file named localhost_access_log_sample.{DATE}.log inside the {WSO2AS_HOME}/repository/logs directory.
The pattern parameter is used to specify which parts of the request/response needs to be logged. In the above sample, xxx stands for the header name we need to log. Here %{xxx}i stands for the request headers and %{xxx}o stands for the response headers.
Example 1: Logging request headers
The configuration is as follows:
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_test."
suffix=".log"
pattern="%{Content-Type}i %{Accept}i %{Accept-Encoding}i"
resolveHosts="false"/>
This will log the Content-type, Accept and Accept-encoding headers of every request coming to AS.
For an example, here we are going to use the RequestInfoExample that comes with AS, to send the request to.
When we send the following http request:
GET http://<IP>:<PORT>/example/servlets/servlet/RequestInfoExample?abc=xyz
We can see the following log entry in the localhost_access_log_sample.{DATE}.log file.
text/plain; charset=utf-8 */* gzip,deflate,sdch
Example 2: Logging response headers
The configuration is as follows:
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_test."
suffix=".log"
pattern="%{Content-Type}o %{Content-Length}o %{Date}o %{Server}o"
resolveHosts="false"/>
The above will log Content-type, Content-Length, Date and Server headers of every response coming from AS, as follows:
text/html;charset=ISO-8859-1 662 Tue, 09 Jul 2013 11:21:50 GMT WSO2 Carbon
Example 3: Logging other variable values
The configuration is as follows:
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_test."
suffix=".log"
pattern="%r %q %h"
resolveHosts="false"/>
The above will log the first line of the request (method and request URI), Query string (prepended with a '?' if it exists) and Remote hostname (or IP) of every request coming to AS as follows. (For more information on all possible values that can be given in the pattern parameter, go to http://tomcat.apache.org/tomcat-7.0-doc/config/valve.html#Access_Log_Valve)
“GET /example/servlets/servlet/RequestInfoExample?abc=xyz HTTP/1.1” ?abc=xyz 10.100.0.67
Example 4: Logging URL encoded parameters
You can not use the Access Log Valve to log URL encoded parameters. However, you can use the Extended Access Log Valve for this. Here only 2 parts ( className and pattern ) are modified from the previous configuration.
The configuration is as follows:
<Valve className="org.apache.catalina.valves.ExtendedAccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_extended."
suffix=".log"
pattern="x-P(param1) x-P(param2)"
resolveHosts="false"/>
Thereafter, when the POST request is sent together with the URL encoded values param1=value1 and param2=value2:
POST http://<IP>:<PORT>/example/servlets/servlet/RequestInfoExample
The above configuration will log the following:
'value1' 'value2'