fluent/fluentd · error · Fluent::ConfigError

send_keepalive_packet is available for tcp/tls

Error message

send_keepalive_packet is available for tcp/tls

What it means

Error "send_keepalive_packet is available for tcp/tls" thrown in fluent/fluentd.

Source

Thrown at lib/fluent/plugin/in_syslog.rb:151

      if @include_source_host
        if @source_address_key
          raise Fluent::ConfigError, "specify either source_address_key or include_source_host"
        end
        @source_address_key = @source_host_key
      end
      if @source_hostname_key
        if @resolve_hostname.nil?
          @resolve_hostname = true
        elsif !@resolve_hostname # user specifies "false" in config
          raise Fluent::ConfigError, "resolve_hostname must be true with source_hostname_key"
        end
      end

      @_event_loop_run_timeout = @blocking_timeout

      protocol = @protocol_type || @transport_config.protocol
      if @send_keepalive_packet && protocol == :udp
        raise Fluent::ConfigError, "send_keepalive_packet is available for tcp/tls"
      end
    end

    def multi_workers_ready?
      true
    end

    def zero_downtime_restart_ready?
      true
    end

    def start
      super

      log.info "listening syslog socket on #{@bind}:#{@port} with #{@protocol_type || @transport_config.protocol}"
      case @protocol_type || @transport_config.protocol
      when :udp then start_udp_server
      when :tcp then start_tcp_server

View on GitHub (pinned to dd45c6e18d)

When it happens

Trigger: Thrown at lib/fluent/plugin/in_syslog.rb:151 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• SSL/TLS and certificate errors — how TLS handshakes and certificate validation fail.

AI-assisted analysis of fluent/fluentd@dd45c6e18d (2026-08-21). Data as JSON: /api/errors/a548adaa3f3879e4. Report an issue: GitHub.