Pipeline definition
The job of ingest nodes is to preprocess 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.
Getting ready
You need an up-and-running Elasticsearch installation, as we described in the Downloading and installing Elasticsearch recipe in Chapter 1, Getting Started.
To execute these commands, any HTTP client can be used, such as curl (https://curl.haxx.se/), Postman (https://www.getpostman.com/), or similar. We will use the Kibana console, as it provides code completion and better character escaping for Elasticsearch.
How to do it...
To define an ingestion pipeline, you need to provide a description and some processors, as follows.
Define a pipeline that adds a field called user with the value john:
{ "description": "Add user john field",
  "processors": [
    { "set":...
