Cannot send logstash output to InfluxDB 0.9.6.1

[lstep]

Hello,
I'm trying to export data I collected from a PostgreSQL to an InfluxDB database, as I want to use Grafana, but Grafana doesn't (yet) support PostgreSQL. For this I'm trying to put a logstash between the PostgreSQL and the InfluxDB, using as logstash input the JDBC plugin (works fine 👍), and the logstash output plugin for InfluxDB.
As the influxdb plugin doesn't support InfluxDB 0.9.x servers (yet 😄), I replaced all the official InfluxDB plugin files in /opt/logstash/vendor/bundle/jruby/1.9/gems with the ones from your repository/fork contentfree/logstash-output-influxdb.

Alas, it still doesn't work. When trying to flush the data (sending it to InfluxDB), I get the following error:

Flushing 1 events to http://127.0.0.1:8086/write?db=pmacct&rp=default&precision=ms&u=admin&p=XXXXX - Teardown?  {:level=>:debug, :file=>"logstash/outputs/influxdb.rb", :line=>"170", :method=>"flush"}
Failed to flush outgoing items {:outgoing_count=>1, :exception=>"NoMethodError", :backtrace=>["/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-influxdb-2.0.2/lib/logstash/outputs/influxdb.rb:338:in `quoted'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-influxdb-2.0.2/lib/logstash/outputs/influxdb.rb:222:in `events_to_request_body'", "org/jruby/RubyHash.java:1342:in `each'", "org/jruby/RubyEnumerable.java:757:in `map'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-influxdb-2.0.2/lib/logstash/outputs/influxdb.rb:222:in `events_to_request_body'", "org/jruby/RubyArray.java:2414:in `map'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-influxdb-2.0.2/lib/logstash/outputs/influxdb.rb:219:in `events_to_request_body'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-influxdb-2.0.2/lib/logstash/outputs/influxdb.rb:171:in `flush'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/stud-0.0.22/lib/stud/buffer.rb:219:in `buffer_flush'", "org/jruby/RubyHash.java:1342:in `each'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/stud-0.0.22/lib/stud/buffer.rb:216:in `buffer_flush'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/stud-0.0.22/lib/stud/buffer.rb:159:in `buffer_receive'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-influxdb-2.0.2/lib/logstash/outputs/influxdb.rb:165:in `receive'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.1.1-java/lib/logstash/outputs/base.rb:81:in `handle'", "(eval):26:in `output_func'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.1.1-java/lib/logstash/pipeline.rb:277:in `outputworker'", "/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.1.1-java/lib/logstash/pipeline.rb:194:in `start_outputs'"], :level=>:warn, :file=>"stud/buffer.rb", :line=>"231", :method=>"buffer_flush"}

I'm not a Ruby user, so I don't exactly understand the problem. It says exception=>"NoMethodError" around the line:

  def quoted(value)
    Numeric === value ? value : %Q|"#{value.gsub('"','\"')}"|
  end

Do I need a particular version of Ruby? I'm on an Ubuntu Server (Trusty), with Ruby 1.9.3.4.

• Logstash version 2.1.1-1
• InfluxDB version 0.9.6.1

If that can help understanding the problem is my logstash output block conf file:

output {
   influxdb {
           host => "127.0.0.1"
           user => "admin"
           password => "XXXXX"
           db => "pmacct"
           coerce_values => {
                "port_src" => "integer"
                "port_dst" => "integer"
                "packets" => "integer"
                "bytes" => "integer"
           }
           data_points => {
                "ip_src" => "%{ip_src}"
                "ip_dst" => "%{ip_dst}"
                "port_src" => "%{port_src}"
                "port_dst" => "%{port_dst}"
                "packets" => "%{packets}"
                "bytes" => "%{bytes}"
                "stamp_inserted" => "%{stamp_inserted}"
                "stamp_updated" => "%{stamp_updated}"
           }
        }
}

Thanks for your help