ROMA - A Distributed Key-Value Store in Ruby

ROMA is one of the data storing systems for distributed key-value stores.
It is a completely decentralized distributed system that consists of multiple processes, called nodes, on several machines. It is based on pure P2P architecture
like a distributed hash table, thus it provides high availability and scalability.

ROMA is written in Ruby. However, following choices are available to access to ROMA.

  • Client libraries of Ruby and Java are available.
  • ROMA protocol is compatible with memcached text-based one so that
    any memcached client libraries allows users to interact with ROMA.

More information is here.



  • Ruby >= 2.1.0


Install ROMA

You can simply install ROMA and dependency libralies by using a "gems" command of Ruby as follows.

$ gem install roma

Make routing files

ROMA is required to make the routing files before starting up.
The routing file is stored the routing information of each processes.

$ mkroute localhost_10001 localhost_10002 --replication_in_host

If succeeded, two new files which named localhost_10001.route and localhost_10002.route created in the current directory.
Refer to Commands for more detail information about Shell Commands.

Start up ROMA

Run two processes by using a romad.rb program as follows:

$ romad localhost -p 10001 -d --replication_in_host
$ romad localhost -p 10002 -d --replication_in_host

Refer to Commands for more detail information about Shell Commands.


Like memcached, you can connect to ROMA with telnet. Connect to the ROMA process that you ran above.

$ telnet localhost 10001

You can interact with ROMA in the same way of memcached commands.

set foo 0 0 3 <return>
bar <return>
get foo <return>
VALUE foo 0 3

Refer to Commands for more detail information about ROMA Commands.


Roma is promoted by Rakuten, Inc. and Rakuten Institute of Technology.