Story

Extend the Elasticsearch output configuration to include a field:

    // Nodes is a list of additional URLs of Elasticsearch nodes
    // to use for load-balancing and fail-over.
    //
    // +optional
    Nodes []string `json:"nodes,omitempty"`

If specified, the URLs listed, plus the URL from the Output.URL field, should be configured as the "hosts" in the fluentd elasticsearch plug-in.

Note this is the same pattern as "Brokers" field in the Kafka output config, so that code can be used as a guide.

Acceptance Criteria

• Unit tests to verify the correct fluentd configuration is generated
• Functional test to verify the "Nodes" URLs are used if the main URL is invalid.

Notes

Kibana using "elasticsearch.hosts":
https://www.elastic.co/guide/en/kibana/current/production.html#high-availability
Fluentd using "hosts":
https://docs.fluentd.org/output/elasticsearch#hosts-optional
Vector v0.28-1 is using "endpoints"
https://vector.dev/docs/reference/configuration/sinks/elasticsearch/#endpoints