Default format of log record is not compatible with common logfile format (http://www.w3.org/Daemon/User/Config/Logging.html#common-logfile-format). Although default "pattern" attribute value in

/subsystem=undertow/server=default-server/host=default-host/setting=access-log

is set to "common" the log record looks like this:

127.0.0.1 - - 18/May/2015:17:53:57 +0200 GET / HTTP/1.1 304 -

which is almost perfect but whole date and time segment should be enclosed in brackets - [ Date ] - so log line would look like this:

127.0.0.1 - - [18/May/2015:17:53:57 +0200] GET / HTTP/1.1 304 -

Later format is also one that is used in current jboss-web module.

So when "pattern" attribute is set to "common" the behavior is not correct according to the W3C standard. When I set "pattern" attribute value of "%t" then log record looks like this:

18/May/2015:17:54:34 +0200

It simply looks like there is some misunderstanding in implementation of this particular string. Here is how it is defined in apache: http://httpd.apache.org/docs/1.3/logs.html

[10/Oct/2000:13:55:36 -0700] (%t)