$ gem install fluent-plugin-arrow

<match arrow>
  @type file
  path arrow_test
  <buffer>
    @type arrow_memory
    arrow_format arrow # or parquet
    schema [
      {"name": "key1", "type": "string"},
      {"name": "key2", "type": "uint64"},
      {"name": "key3", "type": "timestamp", "unit": "milli"},
      {"name": "key4", "type": "list", "field": {"name": "value", "type": "uint64"}},
      {"name": "key5", "type": "struct", "fields": [
        {"name": "bar1", "type": "uint64"},
        {"name": "bar2", "type": "list", "field": {"name": "value", "type": "string"}}
      ]}
    ]
  </buffer>
  <format>
    @type arrow
  </format>
</match>