Cannot use the null byte (\0) as delimiter in tcp input plugin.

[myungjae1]

• fluentd or td-agent version.
  fluentd v0.12.29

• Environment information, e.g. OS.
  macOS sierra + docker (dockerized fluentd using alpine linux)
  But I figure this issue does not matter with environment.

• Your configuration

<source>
  @type tcp

  tag log
  keep_time_key true
  delimiter "\0"
  port 5170
  bind 0.0.0.0
  format none
</source>

The important part in my configuration is delimiter. I just wanted to use the null byte ("\0" in ruby) as my delimter of tcp input.

• Your problem explanation. If you have an error logs, write it together.

Error logs

/opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/basic_parser.rb:92:in `parse_error!': unexpected back-slash escape character '0' at fluentd.conf line 18,15 (Fluent::ConfigParseError)
 17:   keep_time_key true
 18:   delimiter "\0"

     ---------------^
 19:   port 5170
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/literal_parser.rb:185:in `eval_escape_char'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/literal_parser.rb:90:in `scan_double_quoted_string'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/literal_parser.rb:71:in `scan_string'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/literal_parser.rb:64:in `parse_literal'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/v1_parser.rb:130:in `parse_element'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/v1_parser.rb:95:in `parse_element'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/v1_parser.rb:43:in `parse!'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config/v1_parser.rb:33:in `parse'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/config.rb:30:in `parse'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/supervisor.rb:480:in `read_config'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/supervisor.rb:144:in `start'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/lib/fluent/command/fluentd.rb:173:in `<top (required)>'
	from /opt/ruby/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /opt/ruby/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /opt/ruby/lib/ruby/gems/2.2.0/gems/fluentd-0.12.29/bin/fluentd:5:in `<top (required)>'
	from /opt/ruby/bin/fluentd:22:in `load'
	from /opt/ruby/bin/fluentd:22:in `<main>'

I figure this is because fluentd does not accept the null byte expression when it tries to parse its configurations. There is code like below in lib/fluentd/config/literal_parser.rb.

      def eval_escape_char(c)
        case c
        when '"'
          '"'
        when "'"
          "'"
        when "r"
          "\r"
        when "n"
          "\n"
        when "t"
          "\t"
        when "f"
          "\f"
        when "b"
          "\b"
        when /[a-zA-Z0-9]/
          parse_error! "unexpected back-slash escape character '#{c}'"
        else  # symbols
          c
        end
      end

The null byte expression ("\0") is declined by the regex /[a-zA-Z0-9]/. Is this intented? Is there way to use the null byte as delimiter of tcp input plugin?

[tagomoris]

It's just missed, and looks good to add.
@repeatedly how do you think about this?

[repeatedly]

It seems good.