Unexpected return value of Win32::Ipc#wait_any: #{ipc_idx}

Error message

Unexpected return value of Win32::Ipc#wait_any: #{ipc_idx}

What it means

Error "Unexpected return value of Win32::Ipc#wait_any: #{ipc_idx}" thrown in fluent/fluentd.

Source

Thrown at lib/fluent/supervisor.rb:325

          signame_events = [
            {win32_event: Win32::Event.new("#{@signame}"), action: :stop},
            {win32_event: Win32::Event.new("#{@signame}_HUP"), action: :hup},
            {win32_event: Win32::Event.new("#{@signame}_USR1"), action: :usr1},
            {win32_event: Win32::Event.new("#{@signame}_USR2"), action: :usr2},
            {win32_event: Win32::Event.new("#{@signame}_CONT"), action: :cont},
          ]
          events.concat(signame_events)
        end
        begin
          loop do
            infinite = 0xFFFFFFFF
            ipc_idx = ipc.wait_any(events.map {|e| e[:win32_event]}, infinite)
            event_idx = ipc_idx - 1

            if event_idx >= 0 && event_idx < events.length
              $log.debug("Got Win32 event \"#{events[event_idx][:win32_event].name}\"")
            else
              $log.warn("Unexpected return value of Win32::Ipc#wait_any: #{ipc_idx}")
            end
            case events[event_idx][:action]
            when :stop
              stop(true)
            when :hup
              supervisor_sighup_handler
            when :usr1
              supervisor_sigusr1_handler
            when :usr2
              graceful_reload
            when :cont
              supervisor_dump_handler_for_windows
            when :stop_event_thread
              break
            end
          end
        ensure
          events.each { |event| event[:win32_event].close }

View on GitHub (pinned to dd45c6e18d)

When it happens

Trigger: Thrown at lib/fluent/supervisor.rb:325 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/d13df4980fba5a66. Report an issue: GitHub.