>>      Reporting readyness is admin-friendly, but this can be done
>> trivially, in the s6 fashion; it does not take a library to do.
> https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use
> https://cwe.mitre.org/data/definitions/367.html
> https://isecpartners.github.io/news/research/2015/03/03/recognizing_preventing_toctou.html

     Rainer,

     I agree with you, and it was the first point in my mail, that the 
servers should be able to cope with outages. However let's not be 
extremists. The requirement should be put on widely used professional 
servers, but I think there should remain the possibility to start quick 
private hacks in a dependency-based fashion. In most cases this is going 
to work, because Time_of_check_to_time_of_use issues do not arise all 
the time. In this last case, signalling readyness is easily done by 
writing a newline to standard output - no need for a library.

     Didier