out_datadog: Document dd_hostname configuration option

Added by fluent/fluent-bit#8988

Signed-off-by: Jesse Szwedko <[email protected]>

Author: jszwedko

pipeline/outputs/datadog.md

@@ -24,7 +24,8 @@ Before you begin, you need a [Datadog account](https://app.datadoghq.com/signup)
 | dd_service      | _Recommended_ - The human readable name for your service generating the logs (e.g. the name of your application or database). If unset, Datadog will look for the service using [Service Remapper](https://docs.datadoghq.com/logs/log_configuration/pipelines/?tab=service#service-attribute)." |                                  |
 | dd_source       | _Recommended_ - A human readable name for the underlying technology of your service (e.g. `postgres` or `nginx`). If unset, Datadog will look for the source in the [`ddsource` attribute](https://docs.datadoghq.com/logs/log_configuration/pipelines/?tab=source#source-attribute).                                                                                                                                                                                                                                                                                                                   |                                  |
 | dd_tags         | _Optional_ - The [tags](https://docs.datadoghq.com/tagging/) you want to assign to your logs in Datadog. If unset, Datadog will look for the tags in the [`ddtags' attribute](https://docs.datadoghq.com/api/latest/logs/#send-logs).                                                                                                                                                                                                                                                                                                                                   |                                  |
-| dd_message_key  | By default, the plugin searches for the key 'log' and remap the value to the key 'message'. If the property is set, the plugin will search the property name key.                                                                                                                                                                                                                                                                          |                                  |
+| dd_message_key  | By default, the plugin searches for the key 'log' and remap the value to the key 'message'. If the property is set, the plugin will search the property name key.                                                                                                                                                                                                                                                                                                                                                                                                       |                                  |
+| dd_hostname     | The host that emitted logs should be associated with. If unset, Datadog will expect the host to be set as `host`, `hostname`, or `syslog.hostname` attributes. See Datadog Logs preprocessor documentation for up-to-date recognized attributes.                                                                                                                                                                                                                                                                                                                       |                                  |
 
 ### Configuration File
 
@@ -41,6 +42,7 @@ Get started quickly with this configuration file:
     dd_service  <my-app-service>
     dd_source   <my-app-source>
     dd_tags     team:logs,foo:bar
+    dd_hostname myhost
 ```
 
 ## Troubleshooting