What are ingest pipelines in Elasticsearch?

Ingest pipelines allow you to pre-process documents before they are indexed, without needing Logstash for simple transformations. A pipeline is a sequence of processors that transform the document. Common built-in processors include: set (add/overwrite a field), remove (delete a field), rename (rename a field), grok (parse unstructured text with regex patterns), date (parse a date string into a date field), convert (change field type), and script (run a Painless script). Specify the pipeline during indexing with the ?pipeline=my-pipeline query parameter. Pipelines are ideal for log enrichment, IP geolocation, and data normalization.