Rediex

As part of learning elixir and OTP, I decided to implement the functionality of redis in elixir.

Running Rediex

start the server:

mix run --no-halt

I haven't written a cli client yet but you can use telnet to connect to rediex

telnet <ip> <port>

default ip: 127.0.0.1

default port: 6380

Commands implemented so far

Strings

• GET
• SET
• GETSET
• INCR
• INCRBY
• DECR
• DECRBY
• APPEND

Lists

• LPUSH
• RPUSH
• LPOP
• RPOP

I'll update the README as and when i add more commands

Application details

The Application consists of:

• tcp connection supervisor
• database supervisor
• snapshot worker

TCP Connection supervisor

• rediex uses :gen_tcp to spin up a tcp server
• tcp connection supervisor creates a new Task for every new connection from a client
• the code used in this module is reference from the official mix otp guide

Database supervisor

• the database supervisor spins up N databases(genservers) to execute incoming commands
• Each genserver stores a certain range of keys depending the cluster_size in config.exs

Database registry

• This uses Registry from elixir to register the required databases (genservers)

Snapshot worker

• This is a genserver that calls itself every snapshot_interval, collects state from currently running genservers and saves the merged state in snapshot_path

Supervision tree

Contributing

There are lots of commands to be implemented . You can start with the simple ones and create a PR

Writing a command

• You need to register the command in dispatcher.ex in the @available_commands attribute
• Each command belongs to a Module eg. Strings, Lists
• Each Module is just an API to interact with a particular db (genserver). So you need to add a function that wraps a GenServer call for your command
• Each Command is implemented in ModuleName.Impl . This is where you actually write some logic for the command
• Write a corresponding test for the command you implemented

Running tests

mix test

static code analysis

mix credo --strict

Please run tests and credo and make sure everything is fine before submitting a PR since they are part of the build process.

TODO

• Add persistance (AOF and snapshot)
• tcp server to accept multiple clients
• sample cli client to interact with rediex