[Twisted-Python] Re: In Defense of Taps

Steve Waterbury waterbug at beeblebrox.gsfc.nasa.gov
Wed Feb 12 13:53:05 EST 2003

Moshe Zadka wrote:

> I encourage the "newbies" on the list to speak up: what are *you* planning
> to do with Twisted, and which documents would help you with that.

You asked for it!  Okay, so I'm not exactly a "newbie" (or 
maybe a perennial newbie ;^).  Anyway, I guess I'm an anomaly 
in that I founds taps to be a nice and useful thing, as when I 
started developing our server app, it was just after Glyph wrote 
the "Writing a Twisted Plug-in" doc, so I used that as my sample 
code to start with.  I've attached my pgertap.py file so you can 
get an idea of where we are (I've already described what we're 
*trying* to do in earlier messages to the list).  It's out of 
context, and I'm not using any of the config options yet, but 
there's the idea ...

And as an *exclusive* preview for folks on the twisted list :^),
you can download the PGEF ('Pan Galactic Engineering Framework') 
source and have a closer look (this is definitely alpha!):  


userid:  justsomeguy
passwd:  ans=42

To install it:
1. gunzip, untar, install (python setup.py install)
2. install PostgreSQL if you don't have it yet
3. createdb pgerdb
4. run the shell scripts to load the reference data and the 
   demo database:
       cd PanGalactic/src/sql
   (NOTE!  When this script runs createPgerDbTables.sql, it 
    might look like it's caught in a loop when the "ALTER TABLES"
    run, but don't give up ... 89 tables getting 6 ALTER's each 
    (or more) takes a while ... ;^)
       cd PanGalactic/demo/sql
5. run 'mktap pger', then 'twistd -f pger.tap'

You can fire up an interactive xmlrpc session to try 
out the server (I'll put some demo sessions on the web 
site soon).  

If you are *really* brave, you can try starting 
up the client, but you will need to have wxPython 
( or better), a recent version of ZODB (3.1 or 
better recommended), reportlab, PIL, and log4p (yuck! we 
just haven't had time to change that out yet).  To start 
it, cd into the PanGalactic/pangalactic/client 
dir and run 'python fnord.py'.  By default the client is 
setup to interact with the server on localhost at port 
8080.  Do File/Login and just click 'OK' without entering 
anything ... it's a dummy login for now, but that will 
trigger the client to get the demo data from the server and 
display it.  You can get some ideas by turning on the 
Options/Preferences/Show Tooltips (they are off by default).

The only docs so far are in the code ... best bets are:
(a) the comments in createPgerDbTables.sql 
(b) the docstrings in pangalactic.common modules 
and in pangalactic.repo.registry (which 
is the guts of the O-R mapping I'm using ... t.e.row didn't 
do quite what I wanted).  We have several demos coming up, so 
docs have temporarily fallen by the wayside.  

The tests in PanGalactic/pangalactic/repo/tests are very 
naive and (obviously) not real unit tests yet, but they 
are useful to *me*, anyway!

I'd be really grateful if a twisted guru could look at the code 
-- at least the "server" code (pangalactic.common, p.repo, p.tools),
and (after the wave of nausea has passed) comment on how it 
could be improved ... or even contribute, as this will be 
open sourced!  I know zillions of things it needs, but 
I'd especially like to hear about the twisted aspects that 
I haven't used properly or have short-circuited somehow.

The only twisted things we're using on the client side so 
far are jelly/unjelly, but we need to use twisted to make 
our client non-blocking ... we just haven't got around to 
integrating it with the twisted loop yet.  

I'd be *ecstatic* if any of the twisted folk who are 
coming to PyCon would like to do a pre-con sprint or a 
post-con sprint with PanGalactic ... we will be at PyCon 
(we're located just north of DC, anyway!).  

-- Steve.
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