The shipper should report itself as FAILED when multiple outputs are configured.

[cmacknz]

The shipper does not support multiple outputs. When multiple outputs are detected in the shipper configuration provided by the agent, the shipper should report itself as in the FAILED state on its next checkin with the agent.

Currently the behaviour configuration multiple outputs is to pick one based on an arbitrary ordering:

elastic-agent-shipper/controller/runner.go

Lines 209 to 220 in 598c8e6

	func outputFromConfig(config output.Config, queue *queue.Queue) (Output, error) {
	if config.Elasticsearch != nil {
	return elasticsearch.NewElasticSearch(config.Elasticsearch, queue), nil
	}
	if config.Kafka != nil && config.Kafka.Enabled {
	return kafka.NewKafka(config.Kafka, queue), nil
	}
	if config.Console != nil && config.Console.Enabled {
	return output.NewConsole(queue), nil
	}
	return nil, errors.New("no active output configuration")
	}

[fearful-symmetry]

This sort of connects to elastic/elastic-agent#1729, since that arbitrary ordering is just because we need to check the config one-by-one before we fully unpack things. At the very least, it will be easy to just check to see if more than one output has enabled: true set.

[pierrehilbert]

@cmacknz / @leehinman could we close this one with the new shipper plan?

[cmacknz]

Beats doesn't support multiple outputs, but there might be some work to do to get the error to present in a nice way (associated with the agent output unit).