Pipeline won't process messages from a stream when they are also going to default stream

[jasonkeller]

Problem description

Pipeline will not process a message from a stream if its also routed to the default stream. Attaching the pipeline to the default stream appears to process messages correctly.

Steps to reproduce the problem

1. Configure a stream to route messages into the stream; let it also fall into the default stream
2. Attach a pipeline to the new stream; observe that it does not process any messages

Environment

• Graylog Version: graylog-server/stable,stable,now 2.2.0-11 all
• Pipeline Processor plugin version: 2.2
• Elasticsearch Version: elasticsearch/unknown,now 2.4.4 all
• MongoDB Version: mongodb/xenial 1:2.6.10-0ubuntu1 amd64
• Operating System: Ubuntu 16.04 Xenial
• Browser version: Windows 10 / Chrome 56

[jasonkeller]

Just discovered that the default processor order (GeoIP, Pipeline, Message Filter Chain) is the cause of this. Ideally should it not be MFC > Pipeline > GeoIP? Doing it in this order, everything appears to work just fine.