regex - FluentD regex parsed values not appearing in Elasticsearch

Question

So I saw there were a few other questions of this type, but none seemed to solve my issue.

I am attempting to take Springboot logs from files, parse out useful information, and send the result to Elasticsearch, and ultimately read from Kibana. My fluentd.conf looks like the following:

<source>
  type tail
  read_from_head true
  path /path/to/log/
  pos_file /path/to/pos_file
  format /^(?<date>[0-9]+-[0-9]+-[0-9]+\s+[0-9]+:[0-9]+:[0-9]+.[0-9]+)\s+(?<log_level>[Aa]lert|ALERT|[Tt]race|TRACE|[Dd]ebug|DEBUG|[Nn]otice|NOTICE|[Ii]nfo|INFO|[Ww]arn?(?:ing)?|WARN?(?:ING)?|[Ee]rr?(?:or)?|ERR?(?:OR)?|[Cc]rit?(?:ical)?|CRIT?(?:ICAL)?|[Ff]atal|FATAL|[Ss]evere|SEVERE|EMERG(?:ENCY)?|[Ee]merg(?:ency)?)\s+(?<pid>[0-9]+)\s+---\s+(?<message>.*)$/
  tag my.app
</source>
<match my.app>
 type stdout
</match>
<match my.app>
 type elasticsearch
 logstash_format true
 host myhosthere
 port 9200
 index_name fluentd-app
 type_name fluentd
</match>

Given a typical Springboot log line:

2015-07-16 19:20:04.074 INFO 16649 --- [ main] {springboot message}

By also writing to stdout as a test, I see my parser is resulting in:

{
 "date":"2015-07-16 19:20:04.074",
 "log_level":"INFO",
 "pid":"16649",
 "message":"[ main] {springboot message}"
}

However, when this gets written to Elasticsearch, all that results is:

{
 _index: "fluentd-app-2015.07.16",
 _type: "fluentd",
 _id: "AU6YT5sjvkxiJXWCxeM8",
 _score: 1,
 _source: {
  message: "2015-07-16 19:20:04.074 INFO 16649 --- [ main] {springboot message}",
  @timestamp: "2015-07-16T19:20:04+00:00"
 }
},

From what I had read about fluentd-plugin-elasticsearch I expected _source to contain all of the parsed fields that I see in stdout. I have also tried the grok parser - though it seems apparent the issue lies with understanding of the fluentd elasticsearch plugin. How do I get the fields I parsed to persist to elasticsearch?