fluent/fluentd · error · ArgumentError

socket must be a UDPSocket: sock = #{sock}

Error message

socket must be a UDPSocket: sock = #{sock}

What it means

Error "socket must be a UDPSocket: sock = #{sock}" thrown in fluent/fluentd.

Source

Thrown at lib/fluent/plugin_helper/server.rb:534

        def remote_host
          @peeraddr[2]
        end

        def remote_port
          @peeraddr[1]
        end

        def write(data)
          @sock.send(data, 0, @peeraddr[3], @peeraddr[1])
        end
      end

      module EventHandler
        class UDPServer < Coolio::IO
          attr_writer :close_after_write_complete # dummy for consistent method call in callbacks

          def initialize(sock, max_bytes, flags, close_socket, log, under_plugin_development, &callback)
            raise ArgumentError, "socket must be a UDPSocket: sock = #{sock}" unless sock.is_a?(UDPSocket)

            super(sock)

            @sock = sock
            @max_bytes = max_bytes
            @flags = flags
            @close_socket = close_socket
            @log = log
            @under_plugin_development = under_plugin_development
            @callback = callback

            on_readable_impl = case @callback.arity
                               when 1 then :on_readable_without_sock
                               when 2 then :on_readable_with_sock
                               else
                                 raise "BUG: callback block must have 1 or 2 arguments"
                               end
            self.define_singleton_method(:on_readable, method(on_readable_impl))

View on GitHub (pinned to dd45c6e18d)

When it happens

Trigger: Thrown at lib/fluent/plugin_helper/server.rb:534 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of fluent/fluentd@dd45c6e18d (2026-08-21). Data as JSON: /api/errors/0b32ea2c4a295f5f. Report an issue: GitHub.