Kristina Chodorow's Blog
Kristina Chodorow
Kristina is a software engineer at 10gen. She is a maintainer for the MongoDB Perl and Java drivers, wrote and maintains the PHP driver, and has given talks worldwide on MongoDB.
Homepage: http://www.snailinaturtleneck.com
Posts by Kristina Chodorow
Soccer: No Slimy GirlS Allowed!
Jul 10th
Now, I love playing soccer, which I haven’t gotten to do much since high school. Recently, someone created a pickup soccer game meetup for IT professionals (http://www.meetup.com/soccer-nyc/). What with it being geeks+soccer, this sounded awesome, so I requested to join. Denied!
Your request to join NYC Turquoise IT – Soccer For IT Professionals has been declined
The person who declined your request, Xxxxxxxxxx, said:
—————————————————————-
sorry not for girls
—————————————————————-
and he added the “Male only” bullet point to the membership requirements.
WTF? It’s a freakin pickup game! Are they afraid women will get hurt? Sit around buffing our nails? What?
Edit: I just told my cowoker Mike about it and he linked me to http://groups.google.com/group/nyc-pickup-soccer, which is a group he started and thus, he assures me, is coed. Everyone (interested in soccer) should join this group!
How do you make the web reliable?
Jul 3rd
Andrew and I were talking this morning about how we can count on the New York Times to be accurate, but an article linked to by Reddit is often horribly biased. We began thinking about how to hold the web accountable, and we came up with a nifty idea. Make it a wiki/competition/social network. Here’s our plan:
You download a Firefox extension that puts a little “+/- comments” in the corner of your screen. If you’re on a page you like, you click the “+”. If you don’t like the page, you click the “-”. If you have more to say, click “comments” and type in a comment about the page, and anyone visiting the site after you will be able to see it. Clicking “comments” will show you all the comments other people have made about this page, too.
Let’s take an example. Recently, Microsoft put up a page comparing IE8 to other browsers. It was… a bit biased. But there’s no comments section! So, using my handy-dandy extension, I click on “-” because I think it’s a dumb page. Then I click on “comments” and type “biased much?” (clever, eh?). Then I see that someone else made a truly intelligent comment and linked to an impartial comparison. I click on the “+” next to their name, upvoting their comment. Oh, also, I see that the page has been rated -923 by users overall.
Now, I’m totally riffing off of Stack Overflow here, which had the brilliant idea of attaching karma to users. When I upvote a user’s comment, they get 10 karma points. When I downvote, they lose a karma point, and so do I. More karma gives you more privileges.
I’m really psyched about this. It seems like it would be easy to develop the basic idea (basically a user system and a blog system) and there are a zillion features we can add later. Benefits for users:
- Ability to comment on web sites with no comments section (cool ones I’ve thought of are Twitter pages, ftp:// (downloads), and pay sites’ logins (yes, I’m a jerk))
- The satisfaction of gaining karma to gain more power
- Access to other visitors to the site, whom you’d never normally be able to interact with
So, I’m going to try to implement it.
CouchDB vs. MongoDB Benchmark
Jun 29th
Edit (9/1/10): this benchmark is old, silly, and should probably be ignored in favor of more recent and representative ones. I don’t want to take it down for historical purposes, but seriously people, it was never a good benchmark, it’s over a year old at this point, and both databases have changed a lot.
Edit (12/6/09): this is the #1 Google result for “mongodb benchmark”, so I figure I’ll do some community service: if you’re interested in benchmarks, you might want to look at the 3rd party ones listed on the mongodb.org website.
Felix Geisendörfer did a benchmark in PHP that was super-easy for me to port into MongoDB. You can see his post on his blog.
And now… comparing his results for CouchDB with mine for MongoDB’s (I did the graph in Open Office, which is why the quality sucks):
As you can see, MongoDB does, uh, slightly better. Here are the numbers:
| # of Inserts | Couch Total Time (sec) | Couch Time/Doc (ms) | Mongo Total Time (sec) | Mongo Time/Doc (ms) |
|---|---|---|---|---|
| 1 | .0015 | 1.46 | .0005 | .5 |
| 2 | .0015 | .75 | .0004 | .2096 |
| 3 | .0017 | .56 | .0005 | .1604 |
| 4 | .0017 | .44 | .0005 | .1190 |
| 5 | .0018 | .36 | .0005 | .1060 |
| 6 | .0019 | .32 | .0006 | .0931 |
| 7 | .0021 | .3 | .0006 | .0847 |
| 8 | .0022 | .27 | .0007 | .0789 |
| 9 | .0023 | .25 | .0007 | .0734 |
| 10 | .0025 | .25 | .0007 | .0721 |
| 50 | .0072 | .14 | .0024 | .0476 |
| 100 | .0136 | .14 | .0044 | .0442 |
| 500 | .0687 | .14 | .0253 | .0505 |
| 1000 | .1361 | .14 | .0372 | .0372 |
| 2500 | .4686 | .19 | .0278 | .0111 |
| 5000 | .9165 | .18 | .0488 | .0098 |
| 7500 | 1.5116 | .2 | .0835 | .0111 |
| 10000 | 2.3111 | .23 | .1065 | .0107 |
| 25000 | 6.8684 | .27 | .2711 | .0108 |
| 50000 | 15.8227 | .32 | .5430 | .0109 |
| 100000 | 35.3071 | .35 | .1.7697 | .0177 |
| 250000 | 104.0009 | .42 | 6.4533 | .0258 |
| 500000 | 230.6021 | .46 | 11.7684 | .0235 |
| 750000 | 352.7959 | .47 | 17.0473 | .0227 |
| 1000000 | 487.3284 | .49 | 18.4376 | .0184 |
Please let me know if I made any mistakes, all the values were hand-copied.
I ran these tests using the PHP driver on Ubuntu 9.04 on my MacBook Pro. You can see the test script I forked on Github.
A little analysis: Both DBs start with some overhead, but by 1000 inserts CouchDB seems to be chugging along nicely. MongoDB takes slightly longer to hit its groove, hitting its peak around 10000. They both slow a little near the end, as MongoDB starts spending most of its time allocating files and, although I know almost nothing about CouchDB’s structure, I’d guess it’s doing something similar.
Because we are the Mutha Flippin Win
Jun 24th
I’ve been keeping records of funny and nice things people have said about MongoDB. A lot of them can be found at http://www.mongodb.org/display/DOCS/User+Feedback, but there are some good ones that weren’t quite… “right” for the official page. So, slightly off-color, biased, or weird quotes ahoy:
Mailing list:
“Guys at Redmond should get a long course from you about what is the software development and support 
”
-kunthar
Twitter:
@mully It was a well orchestrated effort for @mongodb world domination. I was the shock, @jnunemaker was the awe.
-pengwynn
the @mongodb guys are great! They figure out segfaults, fix bugs and push new builds in practically real time!
-brondsem
Mongo looks like the Mutha Flippin Win. I need to carve some time out to play. http://www.mongodb.org/display/DOCS/Home
-thejohnny
IRC:
“limit=-10 is my hero”
-claymation
Blogs
“It actually has a kind of quirky, yet lovable syntax for defining criteria.”
-http://railstips.org/2009/6/3/what-if-a-key-value-store-mated-with-a-relational-database-system
Revisionist history
May 23rd
I’ve switched out the first ~10 cartoons, and replaced them with one-shot gags. So there are a bunch of new comics to read, starting with the first one.
I’ve always preferred doing The Far Side-/New Yorker-style cartoons, but when I started this site, I thought I should do an ongoing story with characters and plot an all. It turns out that I like killing my characters too much for that to really work out. I hope you enjoy their brief existences.
PHP Extension Wiki
May 16th
I started a wiki on this site (http://www.snailinaturtleneck.com/php) to write down all the stuff I learn about writiing PHP extensions. If anyone else has experience with them, feel free to add or edit articles.
Some basics: a PHP extension is written in C. In fact, PHP itself is written in C, so there’s a lot of good source code to look at out there. There’s an excellent introduction to writing PHP extensions at Zend DevZone. However, it doesn’t go into a lot of the specifics, which is why I started the wiki. I had to figure out how to do a ton of stuff on my own, mostly by digging through the PHP source code and other extensions’ source code. No one should have to look through 500 undocumented C files to figure out how to create a PHP class in C. (However, if you like digging through source code, it’s all available to view on the web. Extensions are under pecl and PHP source is available under php-src.)
I feel like I have a pretty good handle on how to do almost anything with PHP in C, so if anyone has any questions or suggestions for an article, feel free to ask and I’ll try to write a page on it.
Upcoming pages I’d planning on writing:
– Throwing exceptions
– How to extend/implement other classes
– Using HashTable
From Russia with Bugs
May 1st
My Windows partition got a virus. Ugh. Somehow I’ve managed to avoid this, I’ve never gotten a virus on any of my computers before. Anyway, being the geek I am, I decided to get it off my computer without any of this fancy-shmancy (expensive) anti-virus software. My journey:
1. I tried to edit my registry. I got the message: “Your administrator has turned off this function.” Basically, the virus, which had obviously installed itself with whatever permissions my user has, had made it impossible for me to open the registry editor. I’m cool with the registry only being editable by an admin, but then Windows should freakin prompt you for the admin password. And if the virus installed itself when I was logged in, it shouldn’t be able to do admin things!
2. I tried to delete all the virus’s files using Windows Explorer. The virus had deleted “Folder Options” from the menu, so I couldn’t delete hidden files and folders. Why the fsck would Windows let any program remove functionality willy nilly from Explorer?!
3. They could remove the “Show hidden files and folders” option from the GUI, but I’m a Linux programmer. I can just use the command line. Well, the Windows command line is awful. Or hard to use. Or both. I couldn’t make any headway with it. I couldn’t even make it do the equivalent of “ls -a”.
4. The virus put executables in system32, c:\, and other folders that should be only writable by the administrator.
Anyway, that’s why I haven’t put up any new cartoons this week. I’m not sure what to do now. A combination of the virus and Windows itself has totally flummoxed me. I’d like to just get rid of Windows, but I need it for Photoshop.
Get on the bus, Gus
Apr 15th
I booted into OS X today and tried running the unit tests for my PHP driver. It chugged away for a while, then gave me “bus error”. Great. Gotta love C error messages. I narrowed it down to when I insert 253 or more elements into MongoDB. Now, that number was suspiciously close to 256, but I couldn’t think why that would be. I tracked it to the encoding code, then to the _id class code, then to the _id generation code. Surprisingly, it was doing its “bus error” thing before any memory access, it was just reading a file. I suddenly realized that I wasn’t closing the file after reading it, fixed it, and it ran perfectly.
Got Mongo Working on Hostmonster!
Apr 12th
This was written in April of 2009. It is very out of date. See http://rcrisman.net/article/11/installing-mongodb-on-hostmonster-bluehost-accounts for more up-to-date information (as of August 2010). Keep in mind that shared hosting with Hostmonster is very lame. They only lets you run a program for 5 minutes before killing it, so it’s fairly useless to install MongoDB unless you have a dedicated IP.
I finally got MongoDB working on this site, so I’m going to start switching stuff over from MySQL. I’m biased, but I think it’s just an easier database to use.
And, because I like writing tutorials… How I did it:
- Downloaded the binary I created of MongoDB for “legacy” Linux. I originally compiled this for a user on Mandriva 2006 (see previous post about VMWare), but it works fine for other old Linux distros, too.
- Run:
$ tar zxvf mongodb-linux-i686-old-linux-1.tgz
- Make a directory for the database to put files in:
$ mkdir /home/user/data
- Upload libjava.so, libjvm.so, and libverify.so. Make sure they have execute permissions and put them somewhere like /home/user/lib.
- Run:
$ export LD_LIBRARY_PATH=/home/user/lib
replacing the path wherever you put the .so’s above.
- Start the database:
$ cd mongodb-linux-i686-old-linux-1 $ bin/mongod --dbpath /home/user/data --nojni run
I cheated a bit and didn’t install Java, so I had to use the –nojni option. If you install Java, you won’t need that (and you won’t need to upload the individual .so files).
Now, what good is a database if you can’t use it, right? So, I downloaded my PHP driver (go to its Github repository and click “Download” for the latest version). I then followed the install instructions and put the .so generated by make in /home/user/extensions.
I changed the options under “PHP Config” in Hostmonster’s CPanel to use php.ini in /home/user/public_html/php.ini, and then edited that file to use my extension.
I made a simple test page with:
<?php include "Mongo.php"; $m = new Mongo(); echo $m; ?>
Which connected me to MongoDB, showing:
localhost:27017
when I loaded the page!
VM of Death and Doom from Hell
Apr 5th
On Friday at work, I wrote a short post extolling the virtues of VMWare. It was freakin awesome. I had to debug a problem a user was having on a 3-year-old version of an obscure Linux distro, so Eliot (my boss) suggested using VMWare. It was so cool. I found a site that actually still had the distro available, downloaded it, installed it on a virtual machine, and got the exact same error the user was getting! Awesome.
Then I went home, figuring I’d work on it more when I got there.
When I got home… my wireless internet didn’t work. The kernel module for it wouldn’t even load, and when I ran ifconfig, it printed two new interfaces: vmnet1 and vmnet2. It turns out VMWare does something to some types of kernel modules. Damn you, VMWare!
For some reason, I’ve always had computers with Atheros wireless cards, which are very touchy about things like working. So, I started trying to get it going again. This pretty much describes how it went: http://imgs.xkcd.com/comics/success.png. Around 11pm, I gave up, and decided to leave it until Sunday, when I could look at it with fresh eyes.
Today, I booted into Linux to give it another shot. Or, rather, I attempted to boot into Linux. But, I had somehow messed up the modules in a way that made my system unbootable.
So, now I’m reinstalling Ubuntu.
Here’s hoping I make it to shore before the sharks get me. I’m going to be running VMWare from the OS X side of things from now on.
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