Set processor

Use the Set processor to assign a specific value to a field, creating the field if it doesn't exist or overwriting its value if it does.

To use a set processor:

Select Create → Create processor.
Select Set from the Processor menu.
Set Source Field to the field you want to insert, upsert, or update.
Set Value to the value you want the source field to be set to.

This functionality uses the Elasticsearch Set processor internally, but you configure it in Streamlang. Streamlang doesn't always have 1:1 parity with the ingest processor options and behavior. Refer to Processor limitations and inconsistencies.

YAML reference

In YAML mode, configure the set processor using the following parameters. For the complete Streamlang syntax, refer to the Streamlang reference.

Specify exactly one of value or copy_from.

Parameter	Type	Required	Description
`to`	string	Yes	Target field.
`value`	any	One of `value` or `copy_from`	A literal value to assign.
`copy_from`	string	One of `value` or `copy_from`	A source field to copy the value from.
`override`	boolean	No	When `false`, the target field is only set if it doesn't already exist.

		- action: set
  to: attributes.environment
  value: production

- action: set
  to: attributes.backup_message
  copy_from: body.message
		
	