Dynamically populate the serverHost attribute

The conventional method of setting the serverHost attribute is to configure it via the server_attribute:

<match scalyr.*>
@type scalyr

....
server_attributes {
  "serverHost": "fluentd-host",
}

The hostname can also be populated from the log directly, as the DataSet Fluentd plugin supports an alternative solution that allows a parsed field to be applied as the value of serverHost. All you need to do is to add __origServerHost ${record["host"]} to the record_transformer config ( i.e replacing serverHost with the value of the host field) and set use_hostname_for_serverhost to false. For example,

#scalyr specific options
api_write_token YOUR_SCALYR_WRITE_TOKEN
...
use_hostname_for_serverhost false
...

<filter **>
  @type record_transformer
  <record>
    __origServerHost ${record["host"]}
  </record>
</filter>

Here is an example of the sample message sent to Fluentd

{"msg": "hello world", "host": "hostnameEmbededdinMsg"}

The value of the host parameter is now correctly applied as the serverHost attribute