Question

I’m not understanding how to make a persistent store in Redis. Using the options hash is the only place I saw to pass in a path, and it doesn’t seem to have any effect.

> r = Redis.new({:options => {:path => '~/redis_store'}})
=> #<Redis client v2.2.0 connected to redis://127.0.0.1:6379/0 (Redis v2.9.0)> 
> r['foo']
=> "bar" 
> s = Redis.new({:options => {:path => '~/redis_store2'}})
 => #<Redis client v2.2.0 connected to redis://127.0.0.1:6379/0 (Redis v2.9.0)> 
> s['foo']
=> "bar" 

Answer 1

Redis is already a persistent store, and the :path option you found is to designate a unix socket to use to talk to the running Redis server in lieu of a TCP connection (supported in Redis 2.2), not to designate an actual database file.

Are you trying to be able to have isolated databases, so that when you set r['foo'] = 'bar', s['foo'] still returns nil?

If so, Redis lets you connect to multiple numbered databases, the default being #0 (this is what the /0 is in connected to redis://127.0.0.1:6379/0). To choose a different database:

r = Redis.new
=> #<Redis client v2.2.0 connected to redis://127.0.0.1:6379/0 (Redis v2.9.0)> 
r['foo'] = 'bar'

s = Redis.new(:db => 1)
=> #<Redis client v2.2.0 connected to redis://127.0.0.1:6379/1 (Redis v2.9.0)> 
s['foo']
# => nil