[mnet-devel] config policy

[Zooko]

1.  Libraries and modules do not get a config file.  Instead whichever code 
    *uses* the library or module passes configuration options in at runtime.

1a. Applications that end-users actually use get to have a config file.

2.  Things that end-users shouldn't change unless they are Python hackers 
    should *not* be config file options -- they should be hardcoded constants 
    in ALL_CAPS at the top of the relevant .py file.

3.  Algorithms should be designed so that they have as few "voodoo constants" 
    and "tweakable parameters" as possible.  Once you have more than three or 
    so tweakable parameters, then you have a combinatorial explosion of 
    possibilities which means (a) you'll never understand how the algorithm 
    actually behaves in *general*, and (b) the vast majority of possible 
    combinations will never have been tested.

    Also, if you need to add voodoo constants and tweakable parameters to make 
    your code perform well then this is a strong indication that your 
    underlying algorithm sucks.

In example, the final version of Mojo Nation had uncounted hundreds of config 
variables.  A functionally similar program that obeyed these policies should 
ideally have less than a dozen -- three booleans to indicate whether you run 
content tracker, relay server, or block server, plus an integer for MB to 
allocate to the block server, plus bandwidth throttling settings, and an IP 
address and port number override to enable firewalls tunnels.


There were more config policy statements that we had sort of informally agreed 
on in an IRC discussion, but I can't find my notes.  Anyone else want to jump 
in?

--Z



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