Kad

A DHT simulator based on Kademlia

Kad is a Distributed Hash Table (DHT) simulator based on Kademlia protocol. The main purpose is to help understand Kademlia protocol and as a sandbox for further experiments around DHTs and Kademlia.

How it works

• Nodes in a network is represented by Erlang processes, which helps us to simulate 1000s of nodes. Each process will behave like a kademlia node with its own routing table and other metadata.

• Instead of RPC calls, we use Erlang Process messaging.

• Process PIDs replaces UDP endpoint

Running

Prerequisite

Install Erlang and Elixir

git clone [email protected]:madclaws/kad.git

There are 2 modes of simulation,

minikad

Minikad works in 6-bit space, ie the keys and the nodes share same 6-bit space, so keys can be numbers from 0-63, likewise nodes. This mode is good for learning how Kademlia works. Its easier to understand, but beware of conflict in the bit-space.

megakad

Megakad works in 160-bit space, just like large scale kademlia network, ie the keys and the nodes share same 160-bit space. Given the large bitspace we don't have to worry about conflict btw nodes and keys. Also in megakad the keys can be basically any erlang term unlike in minikad it must be an integer (0-63)

Upon starting the sim, it also opens erlang's observer for further observability into the nodes and states.

Open a terminal and run

iex --sname term1@localhost -S mix

From the iex shell

iex(term1@localhost) Kad.minikad

OR

iex(term1@localhost) Kad.megakad

In another terminal

iex --sname term2@localhost -S mix

# connect_term, connects 2 separate terminals using distributed Elixir

iex(term2@localhost) Kad.connect_term

# This example is running minikad on first terminal
iex(term2@localhost) Kad.put(50, 55, "apple")

iex(term2@localhost) Kad.get(2, 55) # "apple"

See the logs in terminal1 and do the operations in terminal2

In the above example we add the KV pair (55, "apple") in node_50 And we still get the value of 55, even if queried from node_2

Playing with minikad

Assuming the above setup is done.

Playing with megakad

coming soon...

For megakad

Kad.get("d4f86a7c1e9b5f2d3c8a1b7e5f9d4c2a3e6f8b9d", "apple", "fruit")

Available functions

• Kad.start_node([]) - Adds a new node to the network
• Kad.minikad() - Starts simulation in minikad mode
• Kad.megakad() - Starts simulation in megakad mode
• Kad.get(node_id, k) - Fetch the value from DHT (node_id can be any node_id)
• Kad.put(node_id, k, v) - Puts the key-value in DHT (node_id can be any node_id)
• Kad.show_map(node_id) - Output the local map of given node
• Kad.show_routing_table(node_id) - Outputs the node's local routing table
• Kad.state - Prints the entire internal state of a node

Tests

mix test