Raise warning if Redis version < 4.0.0

Signed-off-by: Balasankar "Balu" C <balasankarc@autistici.org>

lib/system_check/app/redis_version_check.rb

 # frozen_string_literal: true
 
+require 'redis'
+
 module SystemCheck
   module App
     class RedisVersionCheck < SystemCheck::BaseCheck
       MIN_REDIS_VERSION = '2.8.0'
-      set_name "Redis version >= #{MIN_REDIS_VERSION}?"
+      RECOMMENDED_REDIS_VERSION = '4.0.0'
+      set_name "Redis version >= #{RECOMMENDED_REDIS_VERSION}?"
+
+      @custom_error_message = ''
 
       def check?
-        redis_version = run_command(%w(redis-cli --version))
-        redis_version = redis_version.try(:match, /redis-cli (\d+\.\d+\.\d+)/)
+        redis_version = Gitlab::Redis::Queues.with do |redis|
+          redis.info['redis_version']
+        end
+
+        status = true
+
+        if !redis_version
+          @custom_error_message = "Could not retrieve the Redis version. Please check if your settings are correct"
+          status = false
+        elsif Gem::Version.new(redis_version) < Gem::Version.new(MIN_REDIS_VERSION)
+          @custom_error_message = "Your Redis version #{redis_version} is not supported anymore. Update your Redis server to a version >= #{RECOMMENDED_REDIS_VERSION}"
+          status = false
+        elsif Gem::Version.new(redis_version) < Gem::Version.new(RECOMMENDED_REDIS_VERSION)
+          @custom_error_message = "Support for your Redis version #{redis_version} has been deprecated and will be removed soon. Update your Redis server to a version >= #{RECOMMENDED_REDIS_VERSION}"
+          status = false
+        end
 
-        redis_version && (Gem::Version.new(redis_version[1]) > Gem::Version.new(MIN_REDIS_VERSION))
+        status
       end
 
       def show_error
         try_fixing_it(
-          "Update your redis server to a version >= #{MIN_REDIS_VERSION}"
+          @custom_error_message
         )
         for_more_information(
           'gitlab-public-wiki/wiki/Trouble-Shooting-Guide in section sidekiq'