Otel collector remote config example

remote_config_example.yaml

remote_config_sources:
  vault:
    # vault connection config 

  zookeeper:
    # zookeeper connection config 


# any given config key for any component can be replaced with
# $load_from_remote and config loader/parser would replace it
# with whatever is loaded. Whatever is loaded could be a YAML
# sub-tree or any value. Any loaded sub-tree may not contain
# another $load_from_remote so nested $load_from_remotes are
# not allowed to simplify implementation.


# replace entire sub-tree with remote config 
receivers:
  $load_from_remote:
    source: zookeeper 
    key: /receivers

  
# replace a single key with a value
extensions:
  example_extension:
    endpoint: https://some-beacon-endpoint/
    access_token:
      $load_from_remote:
        source: vault 
        key: /tokens/example_extension/access_token

  another_extension:
      template: "tomcat.yaml"
      int_param: 321
      path:
        $from_config_sources:
          source: zookerper
          key: /tomcat/log_file_path

I see we want to support env var substition as well. May be env vars can be seen as yet another remote source? How about something like:

remote_config_sources:
  vault:
    # vault connection config 

  environment:


  another_extension:
      template: "tomcat.yaml"
      int_param: 321
      path:
        $from_config_sources:
          source: environment
          key: TOMCAT_ACCESS_FILE

This would make environment just another pluggable config source and avoid core collector to implement support for env substition out of the box.

To reduce verbosity, may be we can dos something like the following:

remote_config_sources:
  vault:
    config_prefix: vault_

  environment:
    config_prefix: env_


receivers: $vault_/receivers
  # would be same as writing the following
  # $load_from_remote:
  #     source: zookeeper 
  #     key: /receivers

  another_extension:
      template: "tomcat.yaml"
      int_param: 321
      path: $env_TOMCAT_ACCESS_FIILE
      # same as writing the following
      #  path:
      #    $from_config_sources:
      #        source: environment
      #        key: TOMCAT_ACCESS_FILE