fluent/fluentd · error · ArgumentError

BUG: callback not specified

Error message

BUG: callback not specified

What it means

Error "BUG: callback not specified" thrown in fluent/fluentd.

Source

Thrown at lib/fluent/plugin_helper/thread.rb:67

        @_threads_mutex.synchronize{ @_threads.values }.each do |t|
          if t.alive?
            puts "going to kill the thread still running: #{t[:_fluentd_plugin_helper_thread_title]}"
            t.kill rescue nil
            t[:_fluentd_plugin_helper_thread_running] = false
          end
        end
      end

      # Ruby 2.2.3 or earlier (and all 2.1.x) cause bug about Threading ("Stack consistency error")
      #  by passing splatted argument to `yield`
      # https://bugs.ruby-lang.org/issues/11027
      # We can enable to pass arguments after expire of Ruby 2.1 (& older 2.2.x)
      # def thread_create(title, *args)
      #   Thread.new(*args) do |*t_args|
      #     yield *t_args
      def thread_create(title)
        raise ArgumentError, "BUG: title must be a symbol" unless title.is_a? Symbol
        raise ArgumentError, "BUG: callback not specified" unless block_given?
        m = Mutex.new
        m.lock
        thread = ::Thread.new do
          m.lock # run thread after that thread is successfully set into @_threads
          m.unlock
          thread_exit = false
          ::Thread.current[:_fluentd_plugin_helper_thread_title] = title
          ::Thread.current[:_fluentd_plugin_helper_thread_started] = true
          ::Thread.current[:_fluentd_plugin_helper_thread_running] = true
          begin
            yield
            thread_exit = true
          rescue Exception => e
            log.warn "thread exited by unexpected error", plugin: self.class, title: title, error: e
            thread_exit = true
            raise
          ensure
            @_threads_mutex.synchronize do

View on GitHub (pinned to dd45c6e18d)

When it happens

Trigger: Thrown at lib/fluent/plugin_helper/thread.rb:67 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/8d098e7c948f2379. Report an issue: GitHub.