HTTP Access Logging

HTTP access logs help you monitor your application's usage with information such as the persons who access it, how many hits it received, what the errors are, etc. This information is useful for troubleshooting errors. All WSO2 products can enable access logs for the HTTP servlet transport. This servlet transport works on 9443/9763 ports, and it recieves admin/operation requests. Therefore, access logs for the servert transpot is useful for analysing operational/admin-level access details.

See the topics given below to configure the default behaviour of HTTP access logs in WSO2 products.

Configuring access logs for the HTTP servlet transport

As the runtime of WSO2 products is based on Apache Tomcat, you can use the Access_Log_Valve variable in Tomcat as explained below to configure access logs to the HTTP servlet transport:

1. Open the <WSO2_OB_KM_HOME>/repository/conf/tomcat/catalina-server.xml and <WSO2_OB_APIM_HOME>/repository/conf/tomcat/catalina-server.xml files (which is the server descriptor file for the embedded Tomcat integration) 

2. Customize the attributes for the Access_Log_Valve variable shown below. 

   <Valve className="org.apache.catalina.valves.AccessLogValve"
   directory="${carbon.home}/repository/logs"
   prefix="localhost_access_log_sample."
   suffix=".log"
   pattern="combined"

   The attributes that are used by default are explained below. See the descriptions of the Tomcat-supported Access Log Valve attributes and customize the required values.

   directory	The path to the directory that will store the access log file. By default, this is location is set to ${carbon.home}/repository/logs in all WSO2 products.
   prefix	The prefix added to the log file's name.
   suffix	The suffix added to the log file's name. By default, this is .log for all WSO2 products.
   pattern	The attribute defines the format for the log pattern, which consists of the information fields from the requests and responses that should be logged. The pattern format is created using the following attributes: A standard value to represent a particular string. For example, "%h" represents the remote host name in the request. See the list of string replacement values supported by the Tomcat valve. %{xxx}i is used to represent the header in the incoming request (xxx=header value). %{xxx}o is used to represents the header in the outgoing request (xxx=header value). While you can use the above attributes to define a custom pattern, the standard patterns shown below can be used. common (Apache common log pattern): pattern=%h %l %u %t "%r" %s %b combined (Apache combined log pattern): pattern=%h %l %u %t "%r" %s %b "%{Referer}i" "%{User-Agent}i"

3. Restart the server. According to the default configurations, a log file named  localhost_access_log_sample.{DATE}.log  is created inside the <WSO2_OB_KM_HOME>/repository/logs  and <WSO2_OB_APIM_HOME>/repository/logs directories. The log is rotated on a daily basis.

Customizing access logs by pattern

Given below are a few sample configurations for customizing the pattern attribute:

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"
/>

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

The following log entry is recorded 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"
/>

The above 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"
/>

The above sample configuration logs the first line of the request (method and request URI), query string (prepended with a '?' if it exists), and a 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)"
/>

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'