Scaling foursquare with MongoDB meetup

4sq Outrage caused by RAM (64G on EC2) max out (not CPU bounded)
badge calculation based on entire check-in history
Solid state hard drive, significant improvement on matching with RAM
Hadoop for analytics, separate data collection branch on logs
customized MongoDB build with C++ code for location search given prefix
sharding from day 1 with MongoDB, (not using replica set yet)
validating objects in app, correcting if possible
no map reduce on MongoDB yet
original 4sq code is PHP with ... SQL
employee #3

Harry Heymann:
"10% on open source everything"
"XML is wrong"
"if using Java, not with Scala ... , is wrong"

Street Pacman v0.07 on N1 Screen Shot

157 total
73 active installs (46%)

Qmmp got projectM plugin built in

Audacious, Amarok do not. (on my machine, Ubuntu 10.04 repo)

Noticed Autocomplete (J key) in Qmmp and Audacious.

Compiling gccgo Needs Bison and Flex

Following Go installation

It took hours to compile gccgo, 8g tooks less time to setup and run.

Bison and Flex reference

bootstrap comparison failure ()

Can not get Gold linker to work (Ubuntu Lucid)


Chrome (Chromium) Freezes Ubuntu 10.04 on Lenovo T61, Sync Related Issue

Now I got this problem (thanks Google)
on both Chrome and Chromium.

The Caps-Lock indicator flashes when it freezes.

Turning off Sync seems work.

NTFS mobile drive dies ...

After NTFS error message shown on Ubuntu 9.10 when plugin in the mobile drive, I follow its instruction.

chkdsk /f
under windows

It detects lots of file errors and just die, Windows still can not see the drive.

I wonder this command actually does break my files since the implementation to access NTFS file system under Linux might (must) be different from Windows.

Switching back to Ubuntu, all files on the drive seems corrupted (partial images, I/O error)


Recovered most files after doing nothing but wait for one day, still some files lost.
Strange thing to me is those partial files come back as full files.

Life Saved by Openoffice Backup

Tried photorec, ddrescue without success, finally saved by ~/

Lesson is never leave file residing on external drive opened when the drive goes to unattached.

following GAE python tutorial



Deployment URL

GAE currently only supports Python2.5.
On Ubuntu 9.10, I have Python2.5 and Python2.6 both installed. attempts to use SSL to authenticate gmail account.

In reference to
I can use
sudo easy_install-2.6 pyopenssl
to install and use SSL (import ssl) for Python2.6. But
sudo easy_install-2.5 pyopenssl
seems installation successfully but import ssl fails.

I compiled ssl module from source at with
sudo apt-get install libbluetooth-dev
to fix the missing bluetooth.h header
and it finally works.

following the great RobotLegs Hello World Video Tutorial

Tutorial at:


made a build.xml for ant to compile .as files directly into .swf with open sourced Flex SDK, without Flash (Flex) Builder or Flash IDE.

Create an eCommerce Website with Spree in under 1 minute

Spree! (got its sample site running on my server)


Not tried another RoR ecommerce template yet

Rails command line seems much better than WP solution?

Vision in Microscopes




Install git binaries on Godady Linux share host

Godady Linux has no gcc, so need compatible binary, following tutorial

Tried Rackspace Redhat 5.3 and CentOS 5.3 which are x64, therefore their binaries are not usable on godaddy's 32 server. Then compiled git from source on another 32 server (also Cent OS 5.3) and copied the binaries to Godady. It works!


To check Redhat version
cat /etc/redhat_release
Cent OS 5.3

To check glibc difference

My machine:
e@e-laptop:~$ ldd --version
ldd (EGLIBC) 2.10.1

Godaddy share host server:
-bash-3.2$ ldd --version
ldd (GNU libc) 2.5

There are somewhat two different 'libc' (EGLIBC vs. GNU libc)

LINQ and XML in C#

A SQL like language (in query mode) for manipulating dataset.


在L到6 AV下车的Path,一个女生从一乞讨者边走过4,5米,回走,把钱放入杯中

M60, from LGA to 116ST, Columbia

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