Choose pluck_script based on Redis version

Remove byebug and fix linting

Fix line too long

Add hashie dependency

Mock RedisClient instead of Hashie

Fix tests

Fix comparison

Fix indentation

Remove redundant curr directory path

Change constant name

lib/sidekiq/grouping/redis.rb

@@ -1,20 +1,31 @@
 # frozen_string_literal: true
 
-require_relative "./redis_dispatcher"
+require_relative "redis_dispatcher"
 
 module Sidekiq
   module Grouping
     class Redis
       include RedisDispatcher
 
-      PLUCK_SCRIPT = <<-SCRIPT
+      BREAK_VERSION = "6.2.0"
+
+      PLUCK_SCRIPT_GTE_6_2_0 = <<-SCRIPT
         local pluck_values = redis.call('lpop', KEYS[1], ARGV[1]) or {}
         if #pluck_values > 0 then
           redis.call('srem', KEYS[2], unpack(pluck_values))
         end
         return pluck_values
       SCRIPT
 
+      PLUCK_SCRIPT_LT_6_2_0 = <<-SCRIPT
+        local pluck_values = redis.call('lrange', KEYS[1], 0, ARGV[1] - 1)
+        redis.call('ltrim', KEYS[1], ARGV[1], -1)
+        for k, v in pairs(pluck_values) do
+          redis.call('srem', KEYS[2], v)
+        end
+        return pluck_values
+      SCRIPT
+
       def push_msg(name, msg, remember_unique: false)
         redis do |conn|
           conn.multi do |pipeline|
@@ -50,7 +61,7 @@ def pluck(name, limit)
         if new_redis_client?
           redis_call(
             :eval,
-            PLUCK_SCRIPT,
+            pluck_script,
             2,
             ns(name),
             unique_messages_key(name),
@@ -59,7 +70,7 @@ def pluck(name, limit)
         else
           keys = [ns(name), unique_messages_key(name)]
           args = [limit]
-          redis_call(:eval, PLUCK_SCRIPT, keys, args)
+          redis_call(:eval, pluck_script, keys, args)
         end
       end
 
@@ -100,6 +111,26 @@ def unique_messages_key(name)
       def ns(key = nil)
         "batching:#{key}"
       end
+
+      def server_version
+        Sidekiq.redis do |conn|
+          conn.info["redis_version"]
+        end
+      end
+
+      #
+      # The optimized LUA SCRIPT works from Redis greater than or equal to 6.2.
+      # Check Redis version in use and return the suitable PLUCK_SCRIPT
+      #
+      # @return [<Type>] <description>
+      #
+      def pluck_script
+        if Gem::Version.new(server_version) >= Gem::Version.new(BREAK_VERSION)
+          PLUCK_SCRIPT_GTE_6_2_0
+        else
+          PLUCK_SCRIPT_LT_6_2_0
+        end
+      end
     end
   end
 end

spec/modules/redis_spec.rb

@@ -41,4 +41,26 @@
       expect(redis_call(:smembers, unique_key)).to eq []
     end
   end
+
+  describe "#pluck_script" do
+    context "when Redis server version is" do
+      it ">= 6.2.0, selects the corresponding pluck script" do
+        allow_any_instance_of(described_class)
+          .to receive(:server_version)
+          .and_return("6.2.0")
+        expect(redis_service.send(:pluck_script)).to eq(
+          described_class::PLUCK_SCRIPT_GTE_6_2_0
+        )
+      end
+
+      it "< 6.2.0, selects the corresponding pluck script" do
+        allow_any_instance_of(described_class)
+          .to receive(:server_version)
+          .and_return("6.0.0")
+        expect(redis_service.send(:pluck_script)).to eq(
+          described_class::PLUCK_SCRIPT_LT_6_2_0
+        )
+      end
+    end
+  end
 end