UNWATCH for redis cluster

[mdimas]

Since watch takes a keys(s) it appears to be supported on redis cluster, but unwatch raises an AmbiguousNodeError since there is no key specified. Is there a reason why unwatch could not be implemented to get called on all nodes?

[supercaracal]

Hello,

I think that there is a performance issue if cluster has thousand of nodes. But certainly we can send the command to all nodes without errors.

redis-rb/lib/redis/cluster.rb

Lines 148 to 149 in 087a11b

	when 'discard', 'exec', 'multi', 'unwatch'
	raise AmbiguousNodeError, cmd

In client-side-distributed feature case, we can use unwatch command if we specified keys by watch command.

redis-rb/lib/redis/distributed.rb

Lines 805 to 826 in 69ce376

	# Watch the given keys to determine execution of the MULTI/EXEC block.
	def watch(*keys, &block)
	ensure_same_node(:watch, keys) do |node|
	@watch_key = key_tag(keys.first) || keys.first.to_s
	begin
	node.watch(*keys, &block)
	rescue StandardError
	@watch_key = nil
	raise
	end
	end
	end
	# Forget about all watched keys.
	def unwatch
	raise CannotDistribute, :unwatch unless @watch_key
	result = node_for(@watch_key).unwatch
	@watch_key = nil
	result
	end

Also, redis-cluster-proxy supports unwatch command.

UNWATCH (disables multiplexing)

https://github.com/RedisLabs/redis-cluster-proxy/blob/f8dc227a07f4a738b5fd211501bd521f32f1fcbd/COMMANDS.md

So it seems that there is room for improvement for cluster mode in our gem.

redis-rb/test/cluster_commands_on_transactions_test.rb

Lines 28 to 32 in 087a11b

	def test_unwatch
	assert_raises(Redis::Cluster::AmbiguousNodeError) do
	redis.unwatch
	end
	end