I know this answer is a bit old but I stumbled over this when trying to quickly find a simple regex for Tomcat instead of needing to install the TA. In regards to this question, the regex is slightly incorrect. There are three "/" (forward-slashes) that need to be escaped, see below for the correct syntax. Your log file is also in the incorrect format and is likely from the wrong log source. The regex you shown is for tomcat_localhost_access logs. The log you posted looks to be httpd_access logs. Hopefully this might help someone else that stumbles over this in the future. ^(?P<ip>(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|(?:[A-F0-9]{1,4}:){7}[A-F0-9]{1,4})\s-\s(?P<user>(-|\w+))\s\[\d+\/\w+\/\d{4}:\d{2}:\d{2}:\d{2}\s[\+\-]\d{4}\]\s"(?P<method>[A-Z]{3,7})\s(?P<request_uri>[\S]+)\s(?P<protocol>[\w\/\.]+)"\s(?P<status>\d{3})\s(?P<bytes_sent>(?:\d+|-))$ ... View more