```ruby
module ActionSubscriber
  module Middleware
    class ErrorHandler
      include ::ActionSubscriber::Logging

      def initialize(app)
        @app = app
      end

      def call(env)
        job_mutex = ::Mutex.new
        job_complete = ::ConditionVariable.new

        job_mutex.synchronize do
          ::Thread.new do
            job_mutex.synchronize do
              begin
                @app.call(env)
              rescue => error
                logger.error "FAILED #{env.message_id}"
                ::ActionSubscriber.configuration.error_handler.call(error, env.to_h)
              ensure
                job_complete.signal
              end
            end
          end

          # TODO we might want to pass a timeout to this wait so we can handle jobs that get frozen
          job_complete.wait(job_mutex)
        end
      end
    end
  end
end
```

Remove extra thread in error handler - already in a threadpool
user
```ruby
module ActionSubscriber
  module Middleware
    class ErrorHandler
      include ::ActionSubscriber::Logging

      def initialize(app)
        @app = app
      end

      def call(env)
        @app.call(env)
      rescue => error
        logger.error "FAILED #{env.message_id}"
        ::ActionSubscriber.configuration.error_handler.call(error, env.to_h)
      end
    end
  end
end
```
assistant