foo=bar    type=alpha    T=20180306174204527

input {
  file {
    path => "/tmp/data/*.txt"
    start_position => "beginning"
  }
}
filter {
  kv {
    field_split => "t"
    value_split => "="
  }
}
output {
  elasticsearch { hosts => ["elasticsearch:9200"] }
  stdout {
    codec => rubydebug
  }
}

{
          "host" => "07f3051a3bec",
           "foo" => "bar",
       "message" => "foo=barttype=alphatT=20180306174204527",
             "T" => "20180306174204527",
    "@timestamp" => 2019-06-17T13:47:14.589Z,
          "path" => "/tmp/data/ucL12018_03_06.txt",
          "type" => "alpha"
      "@version" => "1",
}

{
...
             "T" => "2018-03-06T17:42:04.527Z",
    "@timestamp" => 2019-06-17T13:47:14.589Z,
...
}