I got the problem two days ago, finally I got the solution also.
It's all about ruby and gem env path, try the following command to install the elasticsearch plugin:
GEM_HOME="/usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/"
GEM_PATH="/usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/"
/usr/lib64/fluent/ruby/bin/fluent-gem install fluent-plugin-elasticsearch
You probably want to change the path to fit your linux system.
Here is the original page, if you can read Japanese:
I hope fluentd team can resovle this troublesome path issue.
在 2013年12月12日星期四UTC+8上午7时47分41秒,Jay Wilson写道: