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ROMA - A Distributed Key-Value Store in Ruby

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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 gem 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 Shell 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.


If you would like to contribute, please...

  1. Fork and git clone it.
  2. Install gems required for development.
  3. Make changes in a branch & add unit tests.
  4. Run Unit Test
  • bundle exec rake (if unit test fails, run it again - it's fickle).
  • Specify STORAGE to test test cases related to storages such as groonga, sqlite3 and dbm.
  1. Create a pull request.

Contributions, improvements, comments and suggestions are welcome!


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