To enable http level request/response logs in Application Server (AS), we can use the Access_Log_Valve which is provided in Tomcat 7. For more information, please go to http://tomcat.apache.org/tomcat-7.0-doc/config/valve.html#Access_Log_Valve.
To enable logging, you have to put the following XML element under /Server/Service/Engine/Host/ in {WSO2AS_HOME}/repository/conf/tomcat/catalina-server.xml and restart the AS server.
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_sample."
suffix=".log"
pattern="%{xxx}i %{xxx}o"
resolveHosts="false"/>
This will create a log file named localhost_access_log_sample.{DATE}.log inside {WSO2AS_HOME}/repository/logs directory.
The pattern parameter is used to specify which parts of the request/response needs to be logged. In the above sample, xxx stands for the header name we need to log. Here %{xxx}i stands for request headers and %{xxx}o stands for response headers.
Example 1: Logging request headers
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${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 which 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
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_test."
suffix=".log"
pattern="%{Content-Type}o %{Content-Length}o %{Date}o %{Server}o"
resolveHosts="false"/>
The above will log Content-type, Content-Length, Date and Server headers of every response coming from AS, as follows.
text/html;charset=ISO-8859-1 662 Tue, 09 Jul 2013 11:21:50 GMT WSO2 Carbon
Example 3: Logging other variable values
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="${carbon.home}/repository/logs"
prefix="localhost_access_log_test."
suffix=".log"
pattern="%r %q %h"
resolveHosts="false"/>
The above will log 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 which can be given in 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. But, you can use ‘Extended Access Log Valve’ for this. Here only 2 parts (className and pattern) are modified from the previous configuration.
Here is the configuration.
<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"/>
Now, when we send following POST request with 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'