Older blog entries for titus (starting at number 178)

19 May 2006 (updated 19 May 2006 at 17:43 UTC) »
haruspex, yeah, I know that the OS X support for network drives is better -- and that may actually be the technical reason behind not supporting FTP that well. Still, it's freakin' annoying when you're trying to set up an anonymous submissions directory; FTP works great on Windows, but is bollocks on OS X for unskilled users.

scotch, a WSGI-based HTTP recording proxy

I finally wrote up some preliminary docs on scotch, a project I first wrote about yesterday. scotch is my solution for recording twill scripts, as well as tracking AJAX Web calls and doing general Web site regression testing. The scotch examples page is probably the place to start, although the front page is more conversational. There are also some simple simple code recipes that demonstrate the potential. (You can grab scotch at the usual place.)

I had a nice e-mail conversation with Ben Bangert about the possibility of using scotch for more clever twill script making. It's always nice to have people grok the tool you just wrote ;).

Paranthetically, it'd be interesting to see if psiphon functionality could be broken out into WSGI middleware playing on top of scotch.proxy. (Here's an article about psiphon</a>.)

all about twisted

Glyph Lefkowitz posted a link to this interesting paper on twisted. Old paper, but still good, I think.


A week or so of links

Debugging: Essential Technological Literacy, via CoolTools; a good-looking book that most programmers should read.

Driving Rails from the command line. I'd write something to do this with WSGI, but I think I already have.

So Close, Yet So Far -- (not) publishing well online.

The Top 10 OSS Games You've Never Played

A process diagram for arguing about Intelligent Design.

Mac OS X and FTP

So, let me get this straight -- you can easily mount a WebDAV folder on your OS X desktop, and you can just as easily mount an FTP site on your desktop. The difference, of course, is that the FTP site can only be mounted read-only! Why? I can only guess... it doesn't seem like it'd be that difficult to do technically. Hell, it works in Windows...

In other news, a lot of OS X FTP GUIs suck. FTP Thingy didn't do a very good job of dealing with anonymous uploads... I recommend Cyberduck if you need a drag&drop FTP solution.

(Fugu is the way to go if you need to give an Apple user an SCP/SFTP interface.)

On Web services...

From an excellent ACMQueue interview with interview with Werner Vogels, Amazon's CTO:

Do we see that customers who develop applications using AWS care about REST or SOAP? Absolutely not! A small group of REST evangelists continue to use the Amazon Web Services numbers to drive that distinction, but we find that developers really just want to build their applications using the easiest toolkit they can find. They are not interested in what goes on the wire or how request URLs get constructed; they just want to build their applications.

...and AJAX

An interesting, if a bit overly self-congratulatory article on AJAX-iness by Joel Spolsky.

Musings on the nature of OSS "marketing"

So I've been working on a fairly kick-ass piece of software I'm calling scotch, which contains a Web recorder/player (scotch.recorder) implemented as WSGI middleware and a Web proxy (scotch.proxy) implemented as a WSGI app. This lets you do obviously cool things like set up a recording proxy server, or do regression testing by recording Web sessions and then playing them back and comparing "now" responses with the "then" responses, or grok precisely how asynchronous HTTP transactions (aka AJAX) are being used by a site. (I've already used it for all three.) I've got a primitive twill translator written for it, and I'm thinking about writing a translator for Selenium, too. The architecture I've chosen -- decoupled WSGI objects -- is very nice because it allows me to chain things arbitrarily; I want to eventually add a cookie cleaner, a reverse proxy system, and an anonymizer, all of which could be swapped in and out as WSGI middleware. Heck, you could even use this as the basis for an "offline" browsing cache, or write a Web frontend that lets you browse through the recording as it's happening, or ... well, let's just say that a lot of tomfoolery could happen. It isn't even Python limited, because of the proxy app -- that can interact with anything in any language, as long as it speaketh HTTP.

My current source of cognitive dissonance here is that I just don't know how to start writing it up, or where to target my development. (I also don't seem to have any time these days, but that's not a problem that can be solved by anyone else. ;) How should I best apply my limited time?

Here are a couple of possible strategies:

  • post what I have, and blog about all the neat, nifty, or just plain cool things I'm doing with it. Hope people care.

  • develop out a few specific applications -- regression testing and twill translator are two obvious ones -- and write articles about using scotch to solve real problems. Hope people care.

  • figure out what other people want to use it for, and let them proselytize it while I introvert on the architecture and coding. Assume people care.

  • start a company, and ... naaaaaah, never mind ;)

All of this boils down to thinking about "marketing", albeit in the OSS world rather than in the world of $$. And in that world I have reached a simple conclusion: marketing doesn't matter, at least at the scale I can do. My two biggest OSS "successes" so far are Cartwheel (used by 100s of biologists) and twill. Neither of these projects was really "marketed" by me; they were immediately useful to other people, who picked 'em up and ran with them. In a badly mixed metaphor, I'm just trying to stay on the horse -- and I really can't steer it very well.

Back to scotch. I think my best bet is to do two things up front: document as well as possible, and release a solid if not well-rounded implementation. If people find it useful, they'll use it; if not, not. It's the "market" at work...


Martin Fowler on Ruby

Evaluating Ruby says nothing hugely new, but does give the whole RoR combo a thumbs up from his ThoughtWorks-y perspective.


Yesterday, I wrote about tracking bugs across bugzilla. Stephen Thorne pointed me towards Malone, a Canonical system for doing just that.


fight fightfight! ;)

...and someone else weighs in.

In other advogato news, bi calls advogato "elitist". Uhh... yeah, sure, if by "elitist" you mean "we use an explicitly simplistic ranking system to keep spam out". We have incredibly low levels of spam on advogato, and I have to say I don't find the ranking system all that elitist. More exclusionary, if anything.


For future reference

The slamd distributed load generation engine.

mocks considered harmful?


asks if mock objects lead to interface skew.

I could probably go off on a long polemic here, but let's see if I can keep it short... Basically, if all you're doing is testing with mocks, then the answer is probably that you're going to screw yourself up.

But let's generalize the question, to see if perhaps there's a deeper truth:

Dear Mr. Touchstone,

I'm using technique X for testing, and I'm only doing unit testing (...or functional testing, or acceptance testing, or integration testing, or regression testing, or UI testing, or smoke testing, or fizzlebar testing...) I'm worried that this is going to cause problems in the future. What should I do?

-- Anxious in Albuquerque

...and my answer:

Dear Anxious,

I think you should consider testing at additional levels. Generally unit testing is not sufficient, because it purposely tests only small, largely independent units of the code. Functional and smoke tests (as in "push button -- does smoke appear?") should be de rigeur for any project; IMO they're as or more important than unit tests.

So that's my answer: there are bigger problems lying in wait! Mock objects are a specific solution to a fairly general problem with unit tests: you can mimic external interfaces that need to interact with your code in fairly stereotyped ways. That stereotyping is a specific weakness of the approach, as well as being the strength that led you there in the first place.

More generally, any time you find yourself relying completely on your unit tests, you're going to be in trouble. Unit tests are a great programmer tool, and they are very useful, but they are not everything.

Someone interviewed me

Pythonthreads just posted a lengthy interview with me. It's been a month or so since I answered the questions, and I'm still fairly happy with my answers!


I read an interesting post a few days ago that discussed the dismal situation with bugs in Linux packages: basically, there's been a proliferation of bugzillas, and you can often no longer have the conversation necessary to fix a bug in any one of the bugzilla sites.

It occurs to me that one possible solution is to build a test case that demonstrates the bug; that's sort of the maximally portable bit of problem documentation necessary, no? Then just post that to the most upstream bugzilla...



I went to GEICO's Web site today to pay our car insurance, and apparently hit a bad URL (retrieved from old e-mail). The error page came up with a Tolkien quote: "Not all who wander are lost." How cool is that?

Mango Sauce

The latest in Google's AdSense misadventures: Mango Sauce banned from adsense. Going by this page, what we have here is an arbitrary decision being made by a lower-level functionary at Google. Read the page & send in your protest...

The mango sauce page itself is pretty interesting. Very racy, but quite entertaining.


This looks cool. Someone should integrate it with twill.

Deleting spam sent to moderatedSourceForge mailing lists

Problem: Sourceforge runs an old version of mailman that doesn't have the nifty new "discard all" button.

Solution: a twill script to automate the process of logging in & clicking "discard" for each message.

(I've mentioned this before, I think, but it's gotten easier with some of the latest additions to twill.)


The PyWX-discuss@lists.sourceforge.net mailing list has 863 request(s)
waiting for your consideration at:


Please attend to this at your earliest convenience. This notice of pending requests, if any, will be sent out daily. ...


% ./twill-sh examples/discard-sf-mailman-msgs -- pywx-discuss
>> EXECUTING FILE examples/discard-sf-mailman-msgs
==> at https://lists.sourceforge.net/lists/admindb/pywx-discuss
Enter list password:
Note: submit is using submit button: name="request_login", value="Let me in..."
-- matches 220
set 220 values total
Note: submit is using submit button: name="submit", value="Submit All Data"
1 of 1 files SUCCEEDED.

(wipes hands together in a "done" gesture)

I don't grok HTTP very good

I spent a lot of time this weekend hacking together two WSGI middleware apps: first, a recorder/playback system, which lets me both record and play back all traffic into and out of a given WSGI application; and second, a WSGI-based transparent proxy app. The ultimate goal, of course, is to enable recording of all Web traffic much like TCPWatch, but in a nice modular WSGI way.

So, the recorder works: I can now place a middleware wrapper around any app, save & pickle everything that goes into and out of the app, and then play it back. That's pretty neat.

The proxy doesn't work. Or, rather, it sort of works: I can browse Google Search and go to many (but not all) Web sites. There is, however, a bug somewhere: none of my Trac sites work, and AJAX stuff seems broken, too. I'm guessing it's in my broken dealing with HTTP 1.1 features; that, or WSGI and proxying just don't go together. (Also plausible, 'cause I'm breaking a number of PEP rules here.)

Depressing. But I'm sure I'm almost there.

(People interested in wading through some really cruddy code can e-mail me to get a copy. But bring your knee-high waders, 'cause it's bad.)


Two new articles

I've put up two new articles -- What is WSGI? An Introduction and Testing WSGI applications with twill -- a (very) brief intro. Both were written for today's SoCal PIGgies meeting.

In the article on testing WSGI applications with twill, I have a doctest example that pretty stubbornly won't work. I hereby publicly appeal to Grig to get it to work ;).

Legal issues with "releasing software into the wild"

A useful reference.

And the moral of the story is...

In this very interesting piece on a company moving to Linux, the lesson was: test. The company had the confidence to switch deployment platforms -- and not just once but twice -- largely because they had a complete testing setup. Or at least that's what I took away from it ;).


Various miscellany...

MIT swipes Caltech cannon; then hits below the belt!


"I say take 'em back with the cannon.  In fact, forget the cannon,"
remarked senior Jeff Phillips.  Those who have been here for a shorter
period of time reacted differently.  Those quotes are not printable.



My sister pointed out this "fluxus" thing. Check it out [pdf]. Not sure what to make of it. To quote,

A piano is lifted by means of a windlass to the height of 2 meters and then
dropped.  This is repeated until the piano or the floor is destroyed.

I think it's a technique that can be used to shatter preconceptions about art and the role of the audience.



I've been enjoying the agile testing mailing list; here's an interesting post where Michael Bolton (the famous tester, not the famous singer) discusses the so-called 'flat cost curve of change' due to agile methods.

avriettea = ennui+belligerent

avriettea, if I never entered the business because I knew in advance that I wouldn't be happy, does that mean that I'm still a defeatist? (That's why I'm in academics, frankly; it keeps me happier, long term, than programming. Bear in mind that science is as or more difficult than most computer jobs, we're just not paid so well.)

Anyway, it's an interesting idea, but I don't understand why sticking with something that you hate simply because leaving would be "weak" is a good path. (Not having anywhere else to go -- that's a different story.)

And yes, it worries me that you write posts like this and talk about playing with large guns ;).


Michigan State University, Software Engineering, and Python

Just got back from MSU, where I gave two talks, one on my computational work and one on my biology research. (I'm applying for a joint CS/biology position there.)

One of the topics that came up frequently was whether or not I was interested in (or capable of ;) teaching CS undergrad courses, given that I have little formal CS training on my resume. My recent activities in agile testing sparked some interest, as did the notion of teaching a software engineering course based on agile methodologies. I also mentioned Greg Wilson's Software Carpentry course as a possible cross-over course for computational scientists.

I also proposed using the vast base of available OSS software as a starting point for an advanced software engineering course. The idea would be to demonstrate problems and solutions on an already-available hunk o' code; things like setting up (or extending) testing, stabilizing APIs, etc. It could actually be combined with a survey course on different languages. Hmm.

Interestingly, people in the department were already investigating the idea of switching to a scripting language -- Python was explicitly named -- for part of an intro-level programming course. (One professor mentioned ALICE, too.) Needless to say I'd be pretty enthusiastic about the opportunity to introduce Python at that level.

I also spent some time proselytizing about agile development techniques to various friends. Yep, I drunk the cool-aid, it seems.


From lesscode:

" The only architecture that matters is the simplest one you can get to solve the problem at hand. "


DNS & mailman, oh my

Spent several hours today wrestling with DNS and mailman. The goal was to consolidate my DNS onto one machine which would then serve to my hosting company's name servers; this has been years in coming, and I finally had all my pins lined up. All went well, except for a weird glitch in the public-facing name servers which ended up disagreeing on some domains. Boiiiinnggg went some mail...

Then it was mailman's turn. I decided to use Debian's mailman install, which worked fine except for some of the standardized yet esoteric places they place config files. /etc/mailman/mm_cfg.py, anyone?

Next up: exim4 and virtual domain hosting.

I'm getting too old for this sh*t.


John, of JohnCompanies.com (my hosting provider), is starting a new service; I betcha can guess what it does from the name ;). Go check it out.


More buildbot

In addition to our buildbot automation hacks, we spent a fair amount of time twiddling our buildbot configuration for the PyCon project. I wrote up some of the configuration file stuff last night. If you're interested in a private "force build" status page, locking master & slave resources, driving builds from svn checkin, or using the @reboot crontab extension to start buildbot on boot, you might be interested in reading it.

More dnspython

I sent the little dns_check module on to Bob Halley, the author of dnspython, and he sent me back a couple of patches for the code. Good stuff. All checked-in and documented now.

Sysadmin tools

This slashdot article infuriated me more than the usual half-troll slashdot article. An MP3 player and a terminal program are sysadmin tools? Bah.

Here are a few of my favorites.

  1. screen -- run multiple programs in a single terminal window, flip between the output, detach and re-attach. Life is good. My all-time favorite; I've been using it ever since Mark Galassi introduced me to it back in the late 80s/early 90s.

  2. VNC -- like screen, but for X11 programs. Bonus: VNC to Flash recorder for screencasting, although that's not really a sysadmin application.

  3. bash 'for' loops at the command line. Silly, I know, but combined with 'cut', 'sort', 'uniq', 'tail', and 'head', I can do tons of things in one long complicated line. I don't actually know how to program in bash beyond this -- I use Python for anything more complicated.

  4. 'find'. Its command line options have gotta be nearly Turing complete. Powerful beyond belief.

  5. supervisor. It's hard to explain how happy I was when I found this Python-based system for starting and restarting persistent processes...

  6. twill. Really. Having a command-line tool to script Web site aliveness tests & (now) DNS checks is pretty handy. I'll probably add some ping-is-the-machine-alive code, too.

I'm sure there's more that I'll remember as soon as I post this.


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