fluent/fluentd · error · Fluent::ConfigError

Missing worker id on <worker> directive

Error message

Missing worker id on <worker> directive

What it means

Error "Missing worker id on <worker> directive" thrown in fluent/fluentd.

Source

Thrown at lib/fluent/root_agent.rb:110

    end

    attr_reader :inputs
    attr_reader :labels

    def source_only_router
      raise "[BUG] 'RootAgent#source_only_router' should not be called when 'with_source_only' is false" unless @source_only_mode.enabled?
      @source_only_buffer_agent.event_router
    end

    def configure(conf)
      used_worker_ids = []
      available_worker_ids = (0..Fluent::Engine.system_config.workers - 1).to_a
      # initialize <worker> elements
      supported_directives = ['source', 'match', 'filter', 'label']
      conf.elements(name: 'worker').each do |e|
        target_worker_id_str = e.arg
        if target_worker_id_str.empty?
          raise Fluent::ConfigError, "Missing worker id on <worker> directive"
        end

        target_worker_ids = target_worker_id_str.split("-")
        if target_worker_ids.size == 2
          first_worker_id = target_worker_ids.first.to_i
          last_worker_id = target_worker_ids.last.to_i
          if first_worker_id > last_worker_id
            raise Fluent::ConfigError, "greater first_worker_id<#{first_worker_id}> than last_worker_id<#{last_worker_id}> specified by <worker> directive is not allowed. Available multi worker assign syntax is <smaller_worker_id>-<greater_worker_id>"
          end
          target_worker_ids = []
          first_worker_id.step(last_worker_id, 1) do |worker_id|
            target_worker_id = worker_id.to_i
            target_worker_ids << target_worker_id

            if target_worker_id < 0 || target_worker_id > (Fluent::Engine.system_config.workers - 1)
              raise Fluent::ConfigError, "worker id #{target_worker_id} specified by <worker> directive is not allowed. Available worker id is between 0 and #{(Fluent::Engine.system_config.workers - 1)}"
            end
            available_worker_ids.delete(target_worker_id) if available_worker_ids.include?(target_worker_id)

View on GitHub (pinned to dd45c6e18d)

When it happens

Trigger: Thrown at lib/fluent/root_agent.rb:110 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/53bc2607fbdbd0a1. Report an issue: GitHub.