FluentdでApacheのエラーログを収集する正規表現 ref: http://qiita.com/y-ken/items/b302b73d0721162ff401

file0.conf

<source>
  type   tail
  path   /var/log/httpd/error_log
  format /^(\[(?<time>[^\]]*)\] \[(?<level>[^\]]+)\] (\[client (?<host>[^\]]*)\] )?(?<message>.*)|(?<message>.*))$/
  time_format %a %b %d %H:%M:%S %Y
  tag    apache.error
  pos_file /var/log/td-agent/apache_error.pos
</source>

# 送り先を Fluentd の標準ログへ出力します
<match apache.error>
  type stdout
</match>

file1.conf

<source>
  type   tail
  path   /var/log/httpd/error_log
  format apache_error
  tag    apache.error
  pos_file /var/log/td-agent/apache_error.pos
</source>

# 送り先を Fluentd の標準ログへ出力します
<match apache.error>
  type stdout
</match>

file2.txt

$ sudo tail -f /var/log/httpd/error_log
[Tue Aug 05 15:48:43 2014] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Tue Aug 05 15:48:43 2014] [notice] Digest: generating secret for digest authentication ...
[Tue Aug 05 15:48:43 2014] [notice] Digest: done
[Tue Aug 05 15:48:43 2014] [notice] Apache/2.2.15 (Unix) DAV/2 configured -- resuming normal operations
[Tue Aug 05 15:48:56 2014] [error] [client ::1] Directory index forbidden by Options directive: /var/www/html/

file3.txt

$ sudo tail -f /var/log/td-agent/td-agent.log
2014-08-05 15:48:43 +0900 apache.error: {"level":"notice","message":"suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)"}
2014-08-05 15:48:43 +0900 apache.error: {"level":"notice","message":"Digest: generating secret for digest authentication ..."}
2014-08-05 15:48:43 +0900 apache.error: {"level":"notice","message":"Digest: done"}
2014-08-05 15:48:43 +0900 apache.error: {"level":"notice","message":"Apache/2.2.15 (Unix) DAV/2 configured -- resuming normal operations"}
2014-08-05 15:48:56 +0900 apache.error: {"level":"error","host":"::1","message":"Directory index forbidden by Options directive: /var/www/html/"}