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Re: [tor-dev] Stem Descriptor Parsers



OK, bringing back to tor-dev...

On 7/5/12 1:44 PM, Damian Johnson wrote:
Hi Norman.

(Taking this off tor-dev@ for the moment until we get things straightened out...)

Actually, this would have been an interesting discussion for the list.
Feel free to add it back in.

The TorExport functionality seems pretty straightforward, but the stem-interesting parts (new descriptor parsers) already seem to be on Ravi's punch-list.

My understanding is that the csv work is to add export (and maybe
import) functionality to the Descriptor class. This would provide
those capabilities to the current ServerDescriptor and
ExtraInfoDescriptor classes in addition to anything we add in the
future like consensus based entities. If it really isn't possible to
do in the Descriptor then it would be an abstract method that's
implemented by Descriptors as we go along.

OK, there's the first confusion on my part; I thought the export functionality was to be something like utility scripts rather than built into stem itself.

So is export intended to be an instance method of descriptor, one that just dumps a single csv line of the instance attributes (maybe subject to some selection of those attributes)? Or a static method that takes a collection?

It seems like it might be awkward to have to hack stem itself to add a new export format (for example). Is this a concern?

Actually, this makes me wonder a bit about what exactly stem is. It seems like it is:

* stem the Tor Control Protocol interface,

and

* stem the (relay, network status,...) descriptor utility library.

It seems that the former is dependent upon the latter (for stem to provide a list of cached descriptor objects, it needs a descriptor utility library that defines those objects), but not the reverse (the utilities don't much care where the descriptors come from). This isn't completely correct, since the descriptor utilities might provide APIs for parsing some source of descriptor(s) (Tor Control message, cached-consensus, metrics), but making the descriptor utility library one module among many in stem makes it seem like they are more intertwined than they appear. Of course, you've been thinking about this a lot longer than have I. Do all the known use-cases make need both an interface to Tor Control and a descriptor utility library? I guess I'm not quite sure what the design philosophy for stem is.

Onionoo is always a possibility, though we'd probably need a bit more guidance on which part to work on (front end, back end, both?).  But regardless, it still seems like it depends on various parsers that Ravi is working on.

For an Onionoo project I would be the main mentor for stem based
parts, and Karsten would mentor the work on Onionoo itself since he
wrote the java version (though I'll still do the code reviews). First
step would be to start a thread with both of us (and tor-dev@) to
figure out milestones.

FYI: at the Tor dev meeting Sathyanarayanan (gsathya.ceg@xxxxxxxxx)
also expressed interest in taking on this project, though with his
summer internship I'm not sure how much time he'll have to help.

Do I understand Onionoo correctly to be basically a small webservice that returns a JSON formatted description of data read from a file based on the HTTP request parameters, along with a program that presumably runs with some frequency to create that file? It seems that at least porting the webservice side to a Django webapp might be a reasonable project for the rest of our summer.

However, the little bit of software development that I learned does make me want to ask: Why a Python port or this component?

	- Norman

--
Norman Danner - ndanner@xxxxxxxxxxxx - http://ndanner.web.wesleyan.edu
Department of Mathematics and Computer Science - Wesleyan University


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