CSE 223B Labs


We have set up a cluster of 10 machines. You should use these for all of the lab assignments:

They are all available exclusively via SSH.

Programming Language

You will write the labs in Google's golang. It is a young language with a syntax somewhere between C/C++ and Python. It comes with a very rich standard library, and language-level support for light-weight but powerful concurrency semantics with go routines and channels.

Here is some key documentation on the language:

You should be able to find a lot of documents about the Go language on the web, especially from the official site. We highly recommend the official Go tutorial (or "Tour") linked above.

The Tribbler Story

Some cowboy programmer wrote a simple online microblogging service called Tribbler and, leveraging the power of the Web, it becomes quite popular. However, the program runs in a single process on a single machine; it does not scale, cannot support many concurrent connections, and is vulnerable to machine crashes. Knowing that you are taking the distributed computing system course at UCSD, he asks you for help. You answered his call and are starting work on this project.

Your goal is to refactor Tribbler into a distributed system, making it more robust and scalable.

Getting Started

The Tribbler project is written in golang and stored in a git repository. To get started, run these commands from the command line on one of the course machines:

$ cd                       # go to your home directory
$ mkdir -p gopath/src      # the path you use for storing golang src
$ cd gopath/src
$ git clone /class/labs/trib
$ git clone /class/labs/triblab
$ export GOPATH=~/gopath
$ go install ./...

You can do some basic testing to see if the framework is in good shape:

$ go test ./trib/...

The basic Tribbler service should now be installed on the system from your home directory. Let's give it a try:

$ ~/gopath/bin/trib-front -init -addr=:rand

The program should show the URL it is running under (it uses a randomly generated port).

Open your browser and type in the given address. For example, if the machine you logged into was vm153.sysnet.ucsd.edu, and Tribbler is running on port 27944, then open http://vm153.sysnet.ucsd.edu:27944. You should see a list of Tribbler users. You can view their tribs and login as them (with no authentication).

This is how Tribbler looks to users. It is a single web page that performs AJAX calls (a type of web-based RPC) to the back-end web server. The webserver then in turn calls the Tribbler logic functions and returns the results back to the Web page in the browser.

If you find it difficult to access the lab machines outside of UCSD's campus, you need to setup the UCSD VPN or use an SSH tunnel. Information about the former is available here.

Source Code Organization

The source code in the trib package repository is organized as follows:

Don't be scared by the number of packages. Most of the packages are very small, and you don't have to interact with all of them at once. All Go language files under the trib directory are less than 2500 lines in total (the beauty of Go!), so these packages aren't huge and intimidating.

Through the entire lab, you do not need to (and should not) modify anything in the trib repository. If you feel that you have to change some code to complete your lab, please first discuss it with the TA. You are always welcome to read the code in the trib repository. If you find a bug and report it, you might get some bonus credit.

Your Job

Your job is to complete the implementation of the triblab package. It is in the second repo that we checked out.

It would be good practice for you to periodically commit your code into your triblab git repo. Only commited files in that triblab will be submitted for grading, so even if you aren't using the git repository for your own version control (pro tip: use it), you will need to commit all of your files at least once right before before turning in. If you've never used git before, make sure you understand what this means before trying to submit your code.

Lab Roadmap

By the end of the labs, you will have an implementation of Tribbler that is scalable and fault-tolerant.


Go has expectations about environment variables. For convenience, you might set these variables in your .bashrc and/or .bash_profile files so that you don't have to execute the commands every time:

export GOPATH=$HOME/gopath
export PATH=$PATH:$GOPATH/bin

We should have Vim and Emacs installed on the machines. If you need to install other utility packages, ask the TA. Note that you do not have sudo permissions on any of the machines; any sudo attempt will be automatically reported, so please don't even try it.

You could also write your code on your own machine if you want to. See Go language's install page for more information. However, you should test and submit your code on the lab machines.


If you feel comfortable with the lab setup, continue on to Lab1.

Last updated: 2017-04-22 20:34:19 -0700 [validate xhtml]