Author: Vikram Bala
Email: vikrambala2002@gmail.com
Code Repository: GitHub Link
Video Demo: Link
What This Is: This project is a application (intended to run on Ubuntu or MacOS Ventura 13.1+) that implements the Chord Distributed Hash Table Protocol, one of the four original DHT protocols, which won an ACM SIGCOMM award in 2011. The application uses the Chord protocol to: 1. Allow users to join a network of other host computers with which they can share files. 2. Provide users with a P2P Document Search-Engine with which they can simply type in a search keyword, and then receive a list of all available documents in the network which match that keyword. The Chord protocol provides (with high probability) that such information is retrieved with O(log N) nodes contacted in an N node network. The nature of this application is reminiscent of many P2P file sharing systems of the past such as Napster and Gnutella, and those served as inspiration for this project. Note that this project doesn't provide the implementation for the actual sending of files between host machines; however, this is trivial to implement given the features that this project provides.
Inspiration: The ideas in this project were originally implemented as my final project for the CIS5530 Networked Systems Class at the University of Pennsylvania (my partners including Ryan Oliver, Helen Rudoler, and Cassandra Horwege), but were only implemented in the NS-3 network simulator. However, I wanted to take this project and create it in the real world, where I could demonstrate its functionality on actual host machines (see video above for demonstration). More specifically, I was interested in gaining a deeper understanding of the Linux networking stack at the OS level, as well as the POSIX pthread library, features which I were not able to use when working with the NS-3 simulator. Implementing the Chord protocol and an associated file search system as an application helped me gain valuable experience in debugging multithreaded, distributed applications, as well as further developing my knowledge of distributed hash table algorithms, networking protocols, serialization, and how to improve the performance of networked systems.
Technology: The application was written in C++14, and uses the POSIX pthreads library, C Sockets library, and OpenSSL library.
Chord Papers: https://pdos.csail.mit.edu/papers/ton:chord/paper-ton.pdf, https://pdos.csail.mit.edu/papers/chord:sigcomm01/chord_sigcomm.pdf
How to Run:
- Compile from root directory of project. Note that openSSL must be installed as it is used to generate a SHA1 hash.
make all
- Edit main.cpp std::maps in order to change node numbers and IP addresses associated with each node.
- Run the application instance on a node via ./chord <Ipv4 address of this node in 4 dotted octet notation>
List of Avaliable Commands in Application:
JOIN (to join the network of hosts) -> JOIN <Node number of node already in Chord ring that this node can contact to join the ring>
RINGSTATE (to have each host in the network print out their successor and predecessor in the Chord ring) -> RINGSTATE
LEAVE (to leave the network and transfer any files stored on this host to the remaining hosts in the network) -> LEAVE
PUBLISH (to publish files stored on this host into the network as well as keywords corresponding to those files) -> SEARCH PUBLISH <file name of file with document to keyword mappings> NOTE: see /keys for example document-keyword mapping files
SEARCH (to search for files in the network which contain all keywords included in the search query) -> SEARCH SEARCH <node number of node in the Chord ring to initiate this search from (this can just be the number of the node you issue the command from)> <keyword 1> <keyword 2> ... <keyword n>