Well that's good. Fantastic. That gives us 20 minutes to save the world and I've got a post office. And it's shut!

Saturday, July 22

Blog

Yuck

Last October/November, I built a statistical trackback spam filter called Snark. It worked very well, blocking about 99.8% of spam without requiring any attention from me, until its data files got wiped by accident during the DDOS attacks last month.

When I got Snark up and running, we were getting on the order of 10,000 trackbacks per day. Almost all spam, obviously, but Snark made short work of those.

In May, the last full month of Snark operations, we received nearly two million trackbacks.

So far this month, we have received four million trackbacks. It's gotten so bad that at the peak of a spam flood, just firing off a CGI script to log the requests was enough to melt Apache.

Yergh.

Posted by: Pixy Misa at 10:37 AM | Comments (2) | Add Comment | Trackbacks (Suck)
Post contains 124 words, total size 1 kb.

Geek

Duh

So I was scratching my head, wondering why my POST-Redirect-GET wasn't working. All I should have to do is to set the location header, set the return status to 303, and go. But all I got is a blank page, no matter what I tried.

...

Okay, yeah, it might help to actually set the status field rather than creating a new "Status" header.

Posted by: Pixy Misa at 12:16 AM | No Comments | Add Comment | Trackbacks (Suck)
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Friday, July 21

Blog

Banned In India!

And Saudi Arabia. And Pakistan. And at one point, South Korea. As Vinnie says:
Why couldn't we have been banned in Turkey instead? It would have saved alot of headache.

Posted by: Pixy Misa at 11:45 PM | No Comments | Add Comment | Trackbacks (Suck)
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Thursday, July 20

Blog

Word of the Day

Condemnuum, n. A spectrum of activities which at one end would hardly raise an eyebrow at a debutante ball and at the other would make a hyena blush.

Posted by: Pixy Misa at 04:23 AM | Comments (2) | Add Comment | Trackbacks (Suck)
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Wednesday, July 19

Rant

I Hate CSS

To add insult to injury, the only browser that seems to work properly in this case is IE. That means my CSS is broken, of course.

Update: When starting with a "known good" version of something and attempting to develop a new system from there, it may prove worthwhile to verify that the "known good" version is, in fact, good. (Which it wasn't, though I'm not yet sure precisely where the problem lies. However, my cleanroom CSS doesn't exhibit the poopy behaviour of the borrowed CSS, so it's in there somewhere.)

Posted by: Pixy Misa at 04:33 AM | Comments (5) | Add Comment | Trackbacks (Suck)
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Thursday, July 13

Geek

Ick

Not to be using CherryPy for static files.

Well, they do tell you that in the documentation. It works just fine, and makes things a lot easier to set up. But it imposes the same level of overhead for static files as it does for dynamic pages.

6ms of overhead when a page takes 10 to 30ms to generate isn't a big problem.

6ms of overhead when a page takes 2ms to fetch from the cache is more of a problem, but it's better than 160ms of overhead.

6ms of overhead for a static file is... not so good.

So now I get to play with mod_rewrite. Because I don't have a live crocodile to shove down my pants.

Update: Oh look, mod_proxy isn't enabled. So I have to recompile Apache before I can use mod_rewrite with [P] tags. I'll leave it for another day, I think.

Posted by: Pixy Misa at 10:15 PM | Comments (4) | Add Comment | Trackbacks (Suck)
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Geek

Got It!

Minx is now pie-ified. That's reduced the overhead per page from about 160ms to something like 6ms. Since a page fetched from the cache takes about 2ms to process, and an individual entry page about 12ms, that makes the whole thing just a little bit zippier.

Need to do some more bug testing and performance testing, but it seems stable in terms of speed and memory after coughing up 60,000 pages. With 10 threads, it uses 11MB of memory, though its virtual memory footprint is 114MB. Not entirely sure why it is allocating all that memory and never using it, but since the only real problem that causes is that I can't have more than about 350 threads running in any one Minx instance (119MB real, 2935MB virtual), I can probably live with it. And that only applies on 32-bit platforms anyway.

One thing I'm not doing right now is running with Psyco. Even in the worst case (cached pages), it gives a performance boost of 20%. But it also leaks memory like Netscape 4.5.

Posted by: Pixy Misa at 04:31 AM | Comments (1) | Add Comment | Trackbacks (Suck)
Post contains 179 words, total size 1 kb.

Geek

Bonk

Python doesn't assign values to variables, it binds names to values.

Need to write that on a stickynote and attach it to my monitor.

Posted by: Pixy Misa at 03:05 AM | No Comments | Add Comment | Trackbacks (Suck)
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Tuesday, July 11

Geek

We Hates It

We hates Python scoping rules. We hates them forever.

(Currently going for a doc crawl on the theory that it can't be that broken.)

Huh.

Okay, the problem I'm having involves modules, threads, and thread-specific global data. I haven't solved the problem with modules yet, but it turns out there was some magic added to Python 2.4 for thread-specific globals (threading.local). That's a comfort, because I knew that worked, but I couldn't figure out how. CherryPy, the web framework I'm using, supports this under 2.3, but it turns out that it's a hack and it's very slow. So I'm not going mad. Or at least, no more than usual.

I'm moving Minx from the test design, where it is a single CGI program (and so each request is perfectly isolated and I can slap the code together any which way) to production, as a multi-threaded persistent server. Which is much more fiddly in terms of structuring the code and variables, but is twenty to thirty times faster.

Up to 95% of the time taken by the CGI version is overhead: starting a shell, then starting a Python interpreter, loading the twenty or so libraries used, opening a connection to MySQL, and so on. The multi-threaded version does all of that once. (Or at worst, once per thread, for a persistent thread pool.) It also uses Psyco, the Python compiler, which adds a 30% to 50% speed boost for this sort of app. For the CGI version, Psyco takes long enough to do the compile that the overall performance is worse in most cases...

Only because the threads weren't actually isolated from one another, it didn't work at all. I could either add an extra parameter to all the roughly 100 functions I've written so far, or I could work out how to do thread-specific globals.

Update: Okay, all is forgiven. The threading.local trick works flawlessly, even with modules. Threading-local global data for one module is not visible in another, but even if that complicates things for me, that's right. They're modules, not include files. So I have thread-local module-local global variables... Yay!

Update: And it works perfectly with CherryPy. I expected that, because it only makes sense that CherryPy would be using the standard threading module, but there's a difference between being the only sensible way to do something and actually testing it.

Posted by: Pixy Misa at 08:34 AM | Comments (5) | Add Comment | Trackbacks (Suck)
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Saturday, July 08

Cool

Of Course I Am

Your results:
You are Wonder Woman

Wonder Woman
75%
Green Lantern
65%
Spider-Man
65%
Robin
55%
Supergirl
55%
Catwoman
50%
The Flash
50%
Hulk
50%
Iron Man
45%
Superman
40%
Batman
30%
You are a beautiful princess
with great strength of character.
Click here to take the "Which Superhero are you?" quiz...

Yes, I cheated. Of course I cheated. I got Spider Man. Twice.

(via Shamus T. Young)

Posted by: Pixy Misa at 12:15 AM | Comments (8) | Add Comment | Trackbacks (Suck)
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