[Ingest Node] pipeline with id [x] does not exist

[mkrauklis (Michael Krauklis)]

I think this is the same problem noted here: https://discuss.elastic.co/t/ingest-node-pipeline-with-id-x-does-not-exist-solved/54436

That thread says "solved" but I see no resolution. Just an inability to reproduce the error. We're still getting the error in later versions.

Details:
ES 5.1.1
Using 2 custom processors
Single node cluster(s)
Has occurred in at least half a dozen clusters

I don't think I could do a better job at noting the specifics than @PatrickKik so I'll quote him:

@PatrickKik

PUT _ingest/pipeline/x
{
"description": "Ingesting Meetup events",
"processors": [ ... ]
}

When I check if my pipeline exists:

GET _ingest/pipeline/x

It comes back the way it should:

{
"pipelines": [
{
"id": "x",
"config": {
"description": "x",
"processors": [ ... ]
}
}
]
}

But when I want to use it:

PUT a/b/c?pipeline=x
{
"z": 0
}

The response is:

{
"error": {
"root_cause": [
{
"type": "illegal_argument_exception",
"reason": "pipeline with id does not exist"
}
],
"type": "illegal_argument_exception",
"reason": "pipeline with id does not exist"
},
"status": 400
}