Elasticsearch provides a large number of built-in processors that increases with every release. In the preceding examples, we have seen the set and the replace ones. In this recipe, we will cover one that's mostly used for log analysis: the grok processor, which is well-known to Logstash users.
Grok processor
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 the commands, every HTTP client can be used, such as curl (https://curl.haxx.se/), postman (https://www.getpostman.com/), or similar. Use the Kibana console, as it provides the code completion and better character escaping...