Enabling HTTP-Level Request/Response Logs

HTTP-level request/response logs help monitor your application's usage activities, such as who is accessing it, how many hits it receives, what the errors are etc. This information is useful for troubleshooting. As the runtime of WSO2 products is based on Apache Tomcat, you can use the Access_Log_Valve variable in Tomcat 7 as explained below to enable HTTP-level request/response logs in WSO2 products. 

Follow the instructions below to enable HTTP level request/response logs:

1. Edit the Access_Log_Valve  variable in the  <PRODUCT_HOME>/repository/conf/tomcat/catalina-server.xml file, using the following configuration:

   <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"/>

   The pattern parameter is used to specify the parts of the request/response that needs to be logged.

   • xxx - stands for the header name we need to log
   • %{xxx}i - stands for the request headers
   • %{xxx}o -  stands for the response headers

   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

   
   

2. Restart the server. This will create a log file named  localhost_access_log_sample.{DATE}.log  inside the <PRODUCT_HOME>/repository/logs directory.

Sample configurations

Given below are a few sample configurations:

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 sample configuration logs the  Content-type, Accept  and Accept-encoding headers of every  request coming to the server. For example, in the following example, we use the RequestInfoExample to send the HTTP request:

GET http://<IP>:<PORT>/example/servlets/servlet/RequestInfoExample?abc=xyz

It records 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 a bove configuration sample logs the  Content-type, Content-Length, Date  and Server headers of every response coming from the server 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 sample configuration logs 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 the server as follows. 

“GET /example/servlets/servlet/RequestInfoExample?abc=xyz HTTP/1.1”      ?abc=xyz     10.100.0.67

Example 4: Logging URL encoded parameters

You cannot use the AccessLogValve to log URL encoded parameters. However, you can use the ExtendedAccessLogValve attribute for this purpose. In this example only two values (namely, 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"/>

Send the POST request together with the URL  encoded values such as  param1=value1  and  param2=value2 as follows:

POST http://<IP>:<PORT>/example/servlets/servlet/RequestInfoExample

The  above sample configuration logs the following:

'value1'     'value2'