anchor.diff:          {undefined, _, _, _} ->
               {error, {missing, "DOCKER_HOST"}};
   
  -        {_, undefined, undefined, undefined} ->
  -            {error, {missing, "DOCKER_CERT_PATH"}};
  +        {URI, undefined, undefined, undefined} ->
  +            connection(URI);
   
           {_, undefined, _, undefined} ->
               {error, {missing, "DOCKER_KEY"}};
  
positive.code: connection(URI, Cert, Key) ->
      [{KeyType, Value, _}] = public_key:pem_decode(Key),
      [{_, Certificate, _}] = public_key:pem_decode(Cert),
      case http_uri:parse(URI) of
          {ok, {_, _, Name, Port, _, _}} ->
              {ok, #{name => Name,
                     cert => Certificate,
                     key => {KeyType, Value},
                     port => Port}};
          {error, _} = Error ->
              Error
      end.
  
  read_file(Path, File) ->
      file:read_file(filename:join(Path, File)).
  
  register_container(#{<<"Id">> := Id,
                       <<"Image">> := Image,
  
negative.code:     end,
      State;
  
  event(#{<<"id">> := Id, <<"status">> := <<"start">>},
        #{name := Name,
          port := Port} = State) ->
  
      URL = binary_to_list(iolist_to_binary(["http://",
                                             Name,
                                             ":",
                                             integer_to_list(Port),
                                             "/containers/",
                                             Id,
                                             "/json"])),
      case httpc:request(get, {URL, []},
                         [],
                         [{body_format, binary}]) of
  
          {ok, {{_, 200, _}, _, Body}} ->
  
              case jsx:decode(Body, [return_maps]) of
                  #{<<"NetworkSettings">> :=  #{<<"Ports">> := null}} ->
                      nothing_to_register;
  
                  #{<<"Config">> := #{<<"Image">> := Image},
                    <<"Id">> := Id,
                    <<"NetworkSettings">> := #{<<"Ports">> := Ports}} ->
                      register_container(#{<<"Image">> => Image,
                                           <<"Id">> => Id,
                                           <<"Ports">> => maps:to_list(Ports)},
                                         State)
              end;
  
          {error, Reason} ->
              error_logger:error_report([{module, ?MODULE},
                                         {line, ?LINE},
                                         {reason, Reason},
                                         {name, Name},
                                         {port, Port},
                                         {id, Id},
                                         {url, URL}])
      end,
      State;
  
  event(_, State) ->
      State.
  
  