Support for Redis Cluster (3.0)

[iandyh]

Hi

Surprisingly, I haven't found too much information on the status of cluster support in Ruby client. I am aware of redis-rb-cluster from @antirez . But apparently, it's not production ready yet.

So any plans in redis-rb? Or when redis-rb-cluster can be merged into redis-rb?

[spuder]

I'm also finding that there is no documented way to follow ASK and MOVED redirections (redis-cli -c)

2.2.0 :014 > redis = Redis.new(:host => "10.10.10.10")
 => #<Redis client v3.2.1 for redis://10.10.10.10:6379/0> 
2.2.0 :015 > redis.get("foo")
Redis::CommandError: MOVED 12365 10.10.10.10:6379
    from /Users/sowen/.rvm/gems/ruby-2.2.0/gems/redis-3.2.1/lib/redis/client.rb:113:in `call'
    from /Users/sowen/.rvm/gems/ruby-2.2.0/gems/redis-3.2.1/lib/redis.rb:789:in `block in get'
    from /Users/sowen/.rvm/gems/ruby-2.2.0/gems/redis-3.2.1/lib/redis.rb:37:in `block in synchronize'
    from /Users/sowen/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize'
    from /Users/sowen/.rvm/gems/ruby-2.2.0/gems/redis-3.2.1/lib/redis.rb:37:in `synchronize'
    from /Users/sowen/.rvm/gems/ruby-2.2.0/gems/redis-3.2.1/lib/redis.rb:788:in `get'
    from (irb):15
    from /Users/sowen/.rvm/rubies/ruby-2.2.0/bin/irb:11:in `<main>'

[iandyh]

@spuder The doc is here: http://redis.io/topics/cluster-spec. It explains how to handle the redirections.

[spuder]

Thanks. I've read that document twice and I'm not able to grok what needs to change. Is this a client side or server side configuration change?

[badboy]

The redirect needs to be handled on the client side.
redis-rb currently does no handling of Cluster, and thus also don't follows the redirect.
redis-rb-cluster is a reference implementation on top of the existing redis-rb, that you can use.
Check its code to see how it handles the redirect.
It might need a bit more work, but it already handles most cases. I'm not sure it should actually end up in redis-rb, but that is up to the maintainers and/or contributors anyway.
If you want to see it get merged in or improve, you're invited to help as best as you can.

[iandyh]

@spuder You didn't pay too much attention to the "Redirection and resharding" section, did you? :) quote from the doc:

A client must be also able to handle -ASK redirections that are described later in this document, otherwise it is not a complete Redis Cluster client.

Anyway, if you want to play with the cluster, redis-rb-cluster is the best bet now. But for production, it still needs more work.

[spuder]

Thanks @iandyh

[danmaz74]

So basically there's still no production ready adapter for Ruby to use Redis cluster? I'm speechless.

[badboy]

Why speechless? This is a community-effort. We're not here to provide you with everything. You're very welcome to help out and improve stuff though.
Not everyone considers Cluster a priority, not everyone has the time and motivation to provide a production-ready client implementation.
Redis Cluster itself is still very new, there are probably not even that many companies out there using it in production yet. If anyone is using Redis Cluster in production, I encourage those to contribute back what they found and built.

[danmaz74]

@badboy it wasn't against anybody in particular, but I was really frustrated (during an emergency) by the fact that it's impossible to reliably use Cluster from Ruby - even if the example client was written in Ruby.

Fortunately (for us) most of our Redis operations are done from Node.js; right now we're considering to actually move the few direct accesses we did from Ruby to Node (ie, Ruby will get the data from Node, not directly from Redis). But if we'll work directly inside Ruby and find anything useful, we'll for sure contribute back.

[agwozdowski]

👍

[raphi]

👍

[CloudMarc]

This from @antirez is super helpful: https://github.com/antirez/redis-rb-cluster

But this really needs to be rolled into the redis-rb client. redis-cluster cannot be said to be "production-ready" if there are no production-ready clients to support it.

[badboy]

@CloudMarc You are free to provide an implementation that satisfies your definition of "production-ready"

[iandyh]

@CloudMarc If you look at the pull requests for redis-rb-cluster, you can see one from me which is my effort to make the client production ready(and currently waiting for review). You can test that branch and provide feedback to me.