There is a section showing how streams are processed internally. Given that a stream is directly added to an input as a stream_id field and the data is then send to the filter chain. Where are pipelines in this process, they are not shown in the filter part of the diagram?
This would indicate that pipelines are processed after the Message Filter Chain and before the GEO-IP resolver. This would also mean things like extractors have also been run.
This would mean that the stream_id is already set before the pipeline processing begins which is the way that I want to use Graylog.