fix: the behavior of subscription in pubsub when nodes are unstable (#396)

Author: supercaracal

lib/redis_client/cluster/pub_sub.rb

@@ -35,11 +35,15 @@ def spawn_worker(client, queue)
           # Ruby VM allocates 1 MB memory as a stack for a thread.
           # It is a fixed size but we can modify the size with some environment variables.
           # So it consumes memory 1 MB multiplied a number of workers.
-          Thread.new(client, queue) do |pubsub, q|
+          Thread.new(client, queue, nil) do |pubsub, q, prev_err|
             loop do
               q << pubsub.next_event
+              prev_err = nil
             rescue StandardError => e
+              next sleep 0.005 if e.instance_of?(prev_err.class) && e.message == prev_err&.message
+
               q << e
+              prev_err = e
             end
           end
         end
@@ -160,7 +164,6 @@ def start_over
           @router.renew_cluster_state
           @state_dict.each_value(&:close)
           @state_dict.clear
-          @queue.clear
           @commands.each { |command| _call(command) }
           break
         rescue ::RedisClient::ConnectionError, ::RedisClient::Cluster::NodeMightBeDown