Merge branch 'redis-version-check-4.0' into 'master'

Raise warning if Redis version < 4.0.0

Closes #213749

See merge request gitlab-org/gitlab!29395

doc/administration/high_availability/redis.md

@@ -8,10 +8,15 @@ type: reference
 
 The following are the requirements for providing your own Redis instance:
 
-- GitLab 12.0 and later requires Redis version 3.2 or higher. Version 3.2 or higher is recommend as this is
-  what ships with the GitLab Omnibus package. Older Redis versions do not
-  support an optional count argument to SPOP which is now required for
-  [Merge Trains](../../ci/merge_request_pipelines/pipelines_for_merged_results/merge_trains/index.md).
+- Redis version 5.0 or higher is recommended, as this is what ships with
+  Omnibus GitLab packages starting with GitLab 12.7.
+- Support for Redis 3.2 is deprecated with GitLab 12.10 and will be completely
+  removed in GitLab 13.0.
+- GitLab 12.0 and later requires Redis version 3.2 or higher. Older Redis
+  versions do not support an optional count argument to SPOP which is now
+  required for [Merge Trains](../../ci/merge_request_pipelines/pipelines_for_merged_results/merge_trains/index.md).
+- In addition, if Redis 4 or later is available, GitLab makes use of certain
+  commands like `UNLINK` and `USAGE` which were introduced only in Redis 4.
 - Standalone Redis or Redis high availability with Sentinel are supported. Redis
   Cluster is not supported.
 - Managed Redis from cloud providers such as AWS ElastiCache will work. If these

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}?"
+      MIN_REDIS_VERSION = '3.2.0'
+      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'
+          'doc/administration/high_availability/redis.md#provide-your-own-redis-instance-core-only'
         )
         fix_and_rerun
       end