The job of ingest nodes is to pre-process the documents before sending them to the data nodes. This process is called a pipeline definition and every single step of this pipeline is a processor definition.
You need an up-and-running Elasticsearch installation as we described in the Downloading and installing Elasticsearch recipe in Chapter 2, Downloading and Setup.
To define an ingestion pipeline, you need to provide a description and some processors, as follows:
We will define a pipeline that adds a field
userwith the value,john:{ "description" : "Add user john field", "processors" : [ { "set" : { "field": "user", "value": "john" } } ] }