fluent-gem install fluent-plugin-couchbase

# install couchbase server 2.0
  http://www.couchbase.com/download

# install libcouchbase
  http://www.couchbase.com/develop/c/current

# install couchbase gem
  gem install couchbase

<match couchbase.**>
  type couchbase      # fluent output plugin file name (sans fluent_plugin_ prefix)
  hostname localhost  # host name
  port 8091           # port name
  pool default        # pool name
  bucket default      # bucket name
  ttl 0               # number of seconds before document expires. 0 = no expiration
  include_ttl false   # store the ttl value w/ each document
</match>

NOTE: requires the following:
      1) Couchbase Server 2.0
      2) libcouch
      3) couchbase gem
      4) update spec/out_couchbase_spec.rb with your
         hostname, port, pool, and bucket prior to running the tests

1) specify multiple nodes?