[HECnet] PyDECnet setup

[Paul Koning]

> On Nov 18, 2021, at 11:49 AM, Dave McGuire <mcguire at neurotica.com> wrote:
> 
> On 11/18/21 9:58 AM, Paul Koning wrote:
>>> I think that's his point though. Having it exit is going to have non-consistent behavior depending on how it's setup.
>> Good point.
>> I'm thinking about whether running all the shutdown code, then cycling back to the startup point, will in fact be a valid implementation of "reload".  If yes that would be fairly easy to do.  In proper Unix fashion it could be triggered by a SIGHUP signal (as well as by some API request).
>> On the node names bit, if people use the syntax "node @nodenames.dat" in the config, where nodenames.dat is the one in the pydecnet samples directory or equivalent, I could imagine a "copy known nodes" feature that (a) updates the in-memory state and (b) writes a new nodenames.dat with that information.
>> A more general "rewrite the config file to reflect volatile changes" would likely be more difficult, but that particular one seems doable.
> 
>  Paul, I think the last thing you need here is yet more suggestions on how to architect the innards of that package, but..
> 
>  What I would do here is have an internal configuration data structure which stores all active configuration and can be modified by different things.  One such thing would be a configuration file parser for startup time use, another might be NICE messages, etc.  Then serialize and store that active configuration in a non-human-readable file.
> 
>  Optionally, you can recreate the human-readable file (handling any user-typed comments would be left as a significant exercise for the reader ;)) instead of storing the serialized data.
> 
>  But the overarching idea is to add an abstraction layer around the internal configuration structure and define a small API to access it from elsewhere in the program.

That makes a lot of sense, in retrospect.  And making it work that way may not be too terribly hard.  

I already have a machine-readable and semi-human-readable data store for the mapper, a file in JSON format.  I've come to like JSON for this sort of thing.  (It's already used in some API stuff.)

So that's a possible answer.  A file like that as the "permanent database", initialized (a) from a config file in the current format and (b) from other places.  A typical PyDECnet startup would just give the permanent file.   

Let me think about this.  

	paul