fluent-plugin-select-if rename to fluent-plugin-select

fluent-plugin-select(out_select) is the non-buffered output plugin that can filter event logs by using ruby script.

This sample config outputs access logs that have status code 200.

<source>
  type tail
  format apache
  path /var/log/httpd-access.log
  tag tag
</source>
<match tag>
  type select
  select record["code"] == "200"
  add_prefix filtered
  timeout 1s
</match>
<match filtered.tag>
  type file
  path output.log
</match>

The parameter "select" can use 3 variables in event log; tag, time, record. The format of time is an integer number of seconds since the Epoch. The format of record is hash.

tag is alternative for add_prefix. The 2 following match directives are same:

<match tag>
  type select
  select record["code"] == "200"
  add_prefix filtered
  timeout 1s
</match>
<match tag>
  type select
  select record["code"] == "200"
  tag filtered.tag
  timeout 1s
</match>