FIX: use Redis replica host and port (#11566)

Introduce Redis `replica` config and deprecate `slave`

app/models/global_setting.rb

@@ -163,6 +163,26 @@ class GlobalSetting
     @message_bus_config = nil
   end
 
+  def self.get_redis_replica_host
+    return redis_replica_host if redis_replica_host.present?
+    redis_slave_host if respond_to?(:redis_slave_host) && redis_slave_host.present?
+  end
+
+  def self.get_redis_replica_port
+    return redis_replica_port if redis_replica_port.present?
+    redis_slave_port if respond_to?(:redis_slave_port) && redis_slave_port.present?
+  end
+
+  def self.get_message_bus_redis_replica_host
+    return message_bus_redis_replica_host if message_bus_redis_replica_host.present?
+    message_bus_redis_slave_host if respond_to?(:message_bus_redis_slave_host) && message_bus_redis_slave_host.present?
+  end
+
+  def self.get_message_bus_redis_replica_port
+    return message_bus_redis_replica_port if message_bus_redis_replica_port.present?
+    message_bus_redis_slave_port if respond_to?(:message_bus_redis_slave_port) && message_bus_redis_slave_port.present?
+  end
+
   def self.redis_config
     @config ||=
       begin
@@ -170,9 +190,9 @@ class GlobalSetting
         c[:host] = redis_host if redis_host
         c[:port] = redis_port if redis_port
 
-        if redis_slave_host && redis_slave_port && defined?(RailsFailover)
-          c[:replica_host] = redis_slave_host
-          c[:replica_port] = redis_slave_port
+        if get_redis_replica_host && get_redis_replica_port && defined?(RailsFailover)
+          c[:replica_host] = get_redis_replica_host
+          c[:replica_port] = get_redis_replica_port
           c[:connector] = RailsFailover::Redis::Connector
         end
 
@@ -194,9 +214,9 @@ class GlobalSetting
         c[:host] = message_bus_redis_host if message_bus_redis_host
         c[:port] = message_bus_redis_port if message_bus_redis_port
 
-        if message_bus_redis_slave_host && message_bus_redis_slave_port
-          c[:replica_host] = message_bus_redis_slave_host
-          c[:replica_port] = message_bus_redis_slave_port
+        if get_message_bus_redis_replica_host && get_message_bus_redis_replica_port
+          c[:replica_host] = get_message_bus_redis_replica_host
+          c[:replica_port] = get_message_bus_redis_replica_port
           c[:connector] = RailsFailover::Redis::Connector
         end
 

config/discourse_defaults.conf

@@ -124,11 +124,11 @@ redis_host = localhost
 # redis server port
 redis_port = 6379
 
-# redis slave server address
-redis_slave_host =
+# redis replica server address
+redis_replica_host =
 
-# redis slave server port
-redis_slave_port = 6379
+# redis replica server port
+redis_replica_port = 6379
 
 # redis database
 redis_db = 0
@@ -151,11 +151,11 @@ message_bus_redis_host = localhost
 # message bus redis server port
 message_bus_redis_port = 6379
 
-# message bus redis slave server address
-message_bus_redis_slave_host =
+# message bus redis replica server address
+message_bus_redis_replica_host =
 
 # message bus redis slave server port
-message_bus_redis_slave_port = 6379
+message_bus_redis_replica_port = 6379
 
 # message bus redis database
 message_bus_redis_db = 0

config/initializers/400-deprecations.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+if !GlobalSetting.skip_redis?
+  if GlobalSetting.respond_to?(:redis_slave_host) && GlobalSetting.redis_slave_host.present?
+    Discourse.deprecate("redis_slave_host is deprecated, use redis_replica_host instead", drop_from: "2.8")
+  end
+
+  if GlobalSetting.respond_to?(:redis_slave_port) && GlobalSetting.redis_slave_port.present?
+    Discourse.deprecate("redis_slave_port is deprecated, use redis_replica_port instead", drop_from: "2.8")
+  end
+
+  if GlobalSetting.respond_to?(:message_bus_redis_slave_host) && GlobalSetting.message_bus_redis_slave_host.present?
+    Discourse.deprecate("message_bus_redis_slave_host is deprecated, use message_bus_redis_replica_host", drop_from: "2.8")
+  end
+
+  if GlobalSetting.respond_to?(:message_bus_redis_slave_port) && GlobalSetting.message_bus_redis_slave_port.present?
+    Discourse.deprecate("message_bus_redis_slave_port is deprecated, use message_bus_redis_replica_port", drop_from: "2.8")
+  end
+end

spec/models/global_setting_spec.rb

@@ -67,13 +67,13 @@ describe GlobalSetting do
   end
 
   describe '.redis_config' do
-    describe 'when slave config is not present' do
+    describe 'when replica config is not present' do
       it "should not set any connector" do
         expect(GlobalSetting.redis_config[:connector]).to eq(nil)
       end
     end
 
-    describe 'when slave config is present' do
+    describe 'when replica config is present' do
       before do
         GlobalSetting.reset_redis_config!
       end
@@ -83,8 +83,8 @@ describe GlobalSetting do
       end
 
       it "should set the right connector" do
-        GlobalSetting.expects(:redis_slave_port).returns(6379).at_least_once
-        GlobalSetting.expects(:redis_slave_host).returns('0.0.0.0').at_least_once
+        GlobalSetting.expects(:redis_replica_port).returns(6379).at_least_once
+        GlobalSetting.expects(:redis_replica_host).returns('0.0.0.0').at_least_once
 
         expect(GlobalSetting.redis_config[:connector]).to eq(RailsFailover::Redis::Connector)
       end