Redis-migrator is a tool to redistribute keys in your redis cluster when its topography has changed.
##How it works
Say you are using Redis::Distributed to distribute your writes and reads across different redis nodes. Redis::Distributed uses consitent hashing algorithm to determine where a command will go. If you changed configuration of your cluster, for example, changed a hostname or added a new node then routes for some of the keys will change too. If you try to read such a key - you won't get a data from its old node.
Redis-migrator takes a list of nodes for your old cluster and list of nodes for your new cluster and determines for which keys routes were changed. Then it moves those keys to new nodes.
##Install
gem install redis_migrator
##Usage
require 'redis_migrator'
# a list of redis-urls for an old cluster
old_redis_hosts = ["redis://host1.com:6379", "redis://host2.com:6379"]
# a list of redis-urls for a new cluster
new_redis_hosts = ["redis://host1.com:6379", "redis://host2.com:6379", "redis://host3.com:6379"]
migrator = Redis::Migrator.new(old_redis_hosts, new_redis_hosts)
migrator.run
##Requirements
- ruby 1.9 or jruby (with --1.9 flag)
- redis >=2.4.14 (only on machine where migrator will be running)
##TODO
- Error handling