i.remove()
        asyncCall.callsPerHost.incrementAndGet()
        executableCalls.add(asyncCall)
        runningAsyncCalls.add(asyncCall)
      }
      isRunning = runningCallsCount() > 0
    }

    // Avoid resubmitting if we can't logically progress
    // particularly because RealCall handles a RejectedExecutionException
    // by executing on the same thread.