fix: client should be able to subscribe multiple channels for Pub/Sub

lib/redis_client/cluster/pub_sub.rb

@@ -3,33 +3,61 @@
 class RedisClient
   class Cluster
     class PubSub
+      MAX_THREADS = Integer(ENV.fetch('REDIS_CLIENT_MAX_THREADS', 5))
+
       def initialize(router, command_builder)
         @router = router
         @command_builder = command_builder
-        @pubsub = nil
+        @pubsub_states = {}
       end
 
       def call(*args, **kwargs)
-        close
-        command = @command_builder.generate(args, kwargs)
-        @pubsub = @router.assign_node(command).pubsub
-        @pubsub.call_v(command)
+        _call(@command_builder.generate(args, kwargs))
       end
 
       def call_v(command)
-        close
-        command = @command_builder.generate(command)
-        @pubsub = @router.assign_node(command).pubsub
-        @pubsub.call_v(command)
+        _call(@command_builder.generate(command))
       end
 
       def close
-        @pubsub&.close
-        @pubsub = nil
+        @pubsub_states.each_value(&:close)
+        @pubsub_states.clear
       end
 
       def next_event(timeout = nil)
-        @pubsub&.next_event(timeout)
+        msgs = collect_messages(timeout).compact
+        return msgs.first if msgs.size == 1
+
+        msgs
+      end
+
+      private
+
+      def _call(command)
+        node_key = @router.find_node_key(command)
+        pubsub = if @pubsub_states.key?(node_key)
+                   @pubsub_states[node_key]
+                 else
+                   @pubsub_states[node_key] = @router.find_node(node_key).pubsub
+                 end
+        pubsub.call_v(command)
+      end
+
+      def collect_messages(timeout)
+        @pubsub_states.each_slice(MAX_THREADS).each_with_object([]) do |chuncked_pubsub_states, acc|
+          threads = chuncked_pubsub_states.map do |_, v|
+            Thread.new(v) do |pubsub|
+              Thread.current[:reply] = pubsub.next_event(timeout)
+            rescue StandardError => e
+              Thread.current[:reply] = e
+            end
+          end
+
+          threads.each do |t|
+            t.join
+            acc << t[:reply]
+          end
+        end
       end
     end
   end

test/redis_client/test_cluster.rb

@@ -186,6 +186,7 @@ def test_global_pubsub
           pubsub = @client.pubsub
           pubsub.call('SUBSCRIBE', "channel#{i}")
           assert_equal(['subscribe', "channel#{i}", 1], pubsub.next_event(0.1))
+          pubsub.close
         end
 
         sub = Fiber.new do |client|
@@ -195,6 +196,7 @@ def test_global_pubsub
           assert_equal(['subscribe', channel, 1], pubsub.next_event(TEST_TIMEOUT_SEC))
           Fiber.yield(channel)
           Fiber.yield(pubsub.next_event(TEST_TIMEOUT_SEC))
+          pubsub.close
         end
 
         channel = sub.resume(@client)
@@ -216,6 +218,7 @@ def test_sharded_pubsub
             assert_equal(['ssubscribe', channel, 1], pubsub.next_event(TEST_TIMEOUT_SEC))
             Fiber.yield(channel)
             Fiber.yield(pubsub.next_event(TEST_TIMEOUT_SEC))
+            pubsub.close
           end
 
           channel = sub.resume(@client)
@@ -224,6 +227,34 @@ def test_sharded_pubsub
         end
       end
 
+      def test_sharded_pubsub_with_multiple_channels
+        if TEST_REDIS_MAJOR_VERSION < 7
+          skip('Sharded Pub/Sub is supported by Redis 7+.')
+          return
+        end
+
+        sub = Fiber.new do |pubsub|
+          assert_empty(pubsub.next_event(TEST_TIMEOUT_SEC))
+          pubsub.call('SSUBSCRIBE', 'chan1')
+          pubsub.call('SSUBSCRIBE', 'chan2')
+          assert_equal(
+            [['ssubscribe', 'chan1', 1], ['ssubscribe', 'chan2', 1]],
+            pubsub.next_event(TEST_TIMEOUT_SEC).sort_by { |e| e[1] }
+          )
+          Fiber.yield
+          Fiber.yield(pubsub.next_event(TEST_TIMEOUT_SEC))
+          pubsub.close
+        end
+
+        sub.resume(@client.pubsub)
+        @client.call('SPUBLISH', 'chan1', 'hello')
+        @client.call('SPUBLISH', 'chan2', 'world')
+        assert_equal(
+          [%w[smessage chan1 hello], %w[smessage chan2 world]],
+          sub.resume.sort_by { |e| e[1] }
+        )
+      end
+
       def test_close
         assert_nil(@client.close)
       end