How to forward a JSON file with FluentD to Graylog2 with a valid time format

I am working on logging with FluentD and Graylog GELF with limited success. I want to forward a JSON file:

<source>
  @type tail
  path /var/log/suricata/eve.json
  pos_file /var/log/td-agent/suri_eve.pos # pos record
  tag ids
  format json
  # JSON time stamp: 2016-02-01T11:52:49.157072+0000
  # this timestamp is ruby's t.strftime("%Y-%m-%dT%H:%M:%S.%6N%z")
  time_format %Y-%m-%dT%H:%M:%S.%6N%z
  time_key timestamp # I show a JSON message below
</source>

<match **>
  @type graylog
  host 1.2.3.4 #(optional; default="localhost")
  port 12201 #(optional; default=9200)
  flush_interval 30
  num_threads 2
</match>

This kicks in, but produces error messages:

2016-02-01 15:30:11 +0000 [warn]: plugin/in_tail.rb:263:rescue in convert_line_to_event: "{\"timestamp\":\"2016-02-01T15:27:09.000087+0000\",\"flow_id\":51921072,\"event_type\":\"flow\",\"src_ip\":\"10.1.1.85\",\"src_port\":59820,\"dest_ip\":\"224.0.0.252\",\"dest_port\":5355,\"proto\":\"UDP\",\"flow\":{\"pkts_toserver\":4,\"pkts_toclient\":0,\"bytes_toserver\":294,\"bytes_toclient\":0,\"start\":\"2016-02-01T15:26:30.393371+0000\",\"end\":\"2016-02-01T15:26:37.670904+0000\",\"age\":7,\"state\":\"new\",\"reason\":\"timeout\"}}" error="invalid time format: value = 2016-02-01T15:27:09.000087+0000, error_class = ArgumentError, error = invalid strptime format - `%Y-%m-%dT%H:%M:%S.%6N%z'"

An original messages looks like this:

{"timestamp":"2016-02-01T15:31:02.000699+0000","flow_id":52015920,"event_type":"flow","src_ip":"10.1.1.44","src_port":49313,"dest_ip":"224.0.0.252","dest_port":5355,"proto":"UDP","flow":{"pkts_toserver":2,"pkts_toclient":0,"bytes_toserver":128,"bytes_toclient":0,"start":"2016-02-01T15:30:31.348568+0000","end":"2016-02-01T15:30:31.759024+0000","age":0,"state":"new","reason":"timeout"}}

So I checked the Ruby docs. I am not too familiar with FluentD but from what I know the time format expression should fit? I tried format=none but that also doesn't work.

Solution

https://github.com/Graylog2/graylog2-server/issues/1761

This is a bug/problem with reserved fields (undocumented) in Graylog2. If you find a similar bug with timestamps, check the linked issue and the dev response.