Elasticsearch output: Documentation claims "upstream" support, but property is unknown

[jrrdev]

Bug Report

Describe the bug

The 5.0 "Upstream servers" section documentation states the following (see here):

Examples of plugins that support this capability include Forward and Elasticsearch.

However, the Elasticsearch output plugin fails to recognize this property at runtime.

To Reproduce

Configure the pipeline with elastic search output plugin with an upstream key :

upstream_servers:
  - name: my-es-cluster
    nodes:
      - name: node-01
        host: 127.0.0.1
        port: 9200

pipeline:
  outputs:
    - name: es
      upstream: my-es-cluster
      http_user: myuser
      http_passwd: mypassword

When starting Fluent Bit, the following error occurs:

[error] [config] es: unknown configuration property 'upstream'. 
The following properties are allowed: index, type, suppress_type_name, http_user, http_passwd, http_api_key, compress, cloud_id,
 cloud_auth, aws_auth, aws_region, aws_sts_endpoint, aws_role_arn, aws_external_id, aws_service_name, aws_profile, logstash_format,
 logstash_prefix, logstash_prefix_separator, logstash_prefix_key, logstash_dateformat, time_key, time_key_format, time_key_nanos,
 include_tag_key, tag_key, buffer_size, path, pipeline, generate_id, write_operation, id_key, replace_dots, current_time_index, trace_output,
 and trace_error.

In the list of allowed properties, there is nothing that look like a config for upstreams.

Note: Interestingly, the host parameter is also missing from the allowed properties listed in the error message.

Your Environment

• Version used: 5.0.3

[cosmo0920]

This feature is still under the development like: #11647 or #7608.