DEV: Upgrade Redis to 4.2.1.

lib/admin_confirmation.rb

@@ -43,7 +43,7 @@ class AdminConfirmation
   end
 
   def self.exists_for?(user_id)
-    Discourse.redis.exists "admin-confirmation:#{user_id}"
+    Discourse.redis.exists? "admin-confirmation:#{user_id}"
   end
 
   def self.find_by_code(token)

lib/cache.rb

@@ -56,7 +56,7 @@ class Cache
 
   def exist?(name)
     key = normalize_key(name)
-    redis.exists(key)
+    redis.exists?(key)
   end
 
   # this removes a bunch of stuff we do not need like instrumentation and versioning

lib/discourse.rb

@@ -487,7 +487,7 @@ module Discourse
   end
 
   def self.readonly_mode?(keys = READONLY_KEYS)
-    recently_readonly? || Discourse.redis.exists(*keys)
+    recently_readonly? || Discourse.redis.exists?(*keys)
   end
 
   def self.pg_readonly_mode?

lib/discourse_redis.rb

@@ -207,17 +207,14 @@ class DiscourseRedis
     end
   end
 
-  # Implement our own because https://github.com/redis/redis-rb/issues/698 has stalled
-  def exists(*keys)
-    keys.map! { |a| "#{namespace}:#{a}" }  if @namespace
+  def exists(*args)
+    args.map! { |a| "#{namespace}:#{a}" } if @namespace
+    DiscourseRedis.ignore_readonly { @redis.exists(*args) }
+  end
 
-    DiscourseRedis.ignore_readonly do
-      @redis.synchronize do |client|
-        client.call([:exists, *keys]) do |value|
-          value > 0
-        end
-      end
-    end
+  def exists?(*args)
+    args.map! { |a| "#{namespace}:#{a}" } if @namespace
+    DiscourseRedis.ignore_readonly { @redis.exists?(*args) }
   end
 
   def mget(*args)