Distributed Key-Value Store

What is it?

Implementation of key-value store running on many Erlang nodes. Its main goal is 'write-read anywhere' design, which means that you can write data to one node and read it from any node from cluster.

Demo

Currently, this project is deployed on two AWS EC2 instances (both on port 1234):

• ec2-35-177-167-64.eu-west-2.compute.amazonaws.com
• ec2-52-47-155-109.eu-west-3.compute.amazonaws.com

You can use following commands in your terminal:

telnet ec2-35-177-167-64.eu-west-2.compute.amazonaws.com 1234
telnet ec2-52-47-155-109.eu-west-3.compute.amazonaws.com 1234

Then type help and push Enter!

Requirements

• Erlang OTP
• Rebar 2

Starting app

Start app automatically (using bash script)

1. Open terminal and execute start.sh

Execute start.sh script in your terminal. In parameters you may describe number of nodes and TCP port for first node (if you specify 3 nodes and port 1000, nodes will get 1000, 1001 and 1002 ports).

Examples:

• ./start.sh -> creates one node on port 1234
• ./start.sh --port 1000 -> creates one node on port 1000
• ./start.sh --nodes 2 -port 1000 -> creates two nodes on port 1000 and 1001
• ./start.sh -n 2 -p 1000 -> same as above (shortened parameter names)
• ./start.sh -n 5 -replication 2 -> five nodes with replication-factor as two (each key-value pair is stored on two nodes)

Start app manually (better for debugging cases)

1. Open terminals

Open at least one terminal (depends on how many nodes you want to have). Go to project root directory.

2. Compile application

Execute rebar clean compile in one terminal.

3. Start Erlang nodes.

Execute erl -pa ebin -sname <your_node_name> in each terminal. <your_node_name> must be unique for each node. Then Erlang shell will be opened.

4. Connect nodes with each other.

In one shell execute net_kernel:connect_node(<another_node_name>) for each node. You can check connected node by nodes() command.

6. Start application

On all nodes execute: store_app:start(<port>). Each node must run on unique port.

Using app

• Connect to any node by telnet:

telnet localhost <choosen_port>

• Use command:

help

Hints:

• Logs for each node are stored in logs/

Todo

Main features

• Connecting new node to existing cluster
• Persistence

Minor fixes

• Make commands in tcp_interface more readable (+ add help command)

Docker deployment

We use docker so as to deploy this project to remote servers.

docker build -t store_app_image
docker save -o images/store_app_image store_app_image
docker load -i images/store_app_image
docker run -p 1234:1234 --name store_app store_app_image <this_node> <master_node> 
# when setting up the first node in the cluster then this_node == master_node

Authors

• Mateusz Kuźmik
• Szymon Jakóbczyk