configure multiple server to support sidekiq - ruby-on-rails

Question

I planned to migrate redis server to a new one with sidekiq running, but doesn't want to stop the current application running. And I don't want to use redis cluster which is still alpha version.
My thought is to ask sidekiq to write to new redis server, but pulls from both of them, so that once the workers in old redis are completed, the new one can totally take over all workers. I think this solution is feasible, but I have no idea how to make it happen.
This is my sidekiq.rb:
sidkiq_config = YAML.load(ERB.new(Rails.root.join('config/redis.yml').read).result)
Sidekiq.configure_server do |config|
config.logger.level = Logger::ERROR
config.redis = { :url => "redis://redis2.staging:6379", :namespace => "app_#{Rails.env}:sidekiq" }
config.redis = { :url => "redis://redis.staging:6379", :namespace => "app_#{Rails.env}:sidekiq" }
end
Sidekiq.configure_client do |config|
config.logger.level = Logger::ERROR
config.redis = { :url => "redis://redis2.staging:6379", :namespace => "app_#{Rails.env}:sidekiq" }
end

Answer 1

I believe the easiest solution is to run two instances of sidekiq - one that reads from the old cluster, and one that reads from the new cluster
sidkiq_config = YAML.load(ERB.new(Rails.root.join('config/redis.yml').read).result)
Sidekiq.configure_server do |config|
config.logger.level = Logger::ERROR
if ENV['read_from_new']
config.redis = { :url => "redis://redis2.staging:6379", :namespace => "app_#{Rails.env}:sidekiq" }
else
config.redis = { :url => "redis://redis.staging:6379", :namespace => "app_#{Rails.env}:sidekiq" }
end
end
Sidekiq.configure_client do |config|
config.logger.level = Logger::ERROR
config.redis = { :url => "redis://redis2.staging:6379", :namespace => "app_#{Rails.env}:sidekiq" }
end

Answer 2

You can update to a recent version of sidekiq and use Sharding.
REDIS_A = ConnectionPool.new { Redis.new(...) }
REDIS_B = ConnectionPool.new { Redis.new(...) }
# To create a new connection pool for a namespaced Sidekiq worker:
ConnectionPool.new do
client = Redis.new(:url => "Your Redis Url")
Redis::Namespace.new("Your Namespace", :redis => client)
end
# Create a job in the default redis instance
SomeWorker.perform_async
# Push a job to REDIS_A using the low-level Client API
client = Sidekiq::Client.new(REDIS_A)
client.push(...)
client.push_bulk(...)
Sidekiq::Client.via(REDIS_B) do
# All jobs defined within this block will go to B
SomeWorker.perform_async
end
To quite sidekiq, click the quite button in the UI