Expose `replica_postgresql_connection` to `ActiveRecord::Base`.

lib/active_record/connection_adapters/postgresql_fallback_adapter.rb

@@ -131,13 +131,7 @@ module ActiveRecord
       if fallback_handler.master_down?
         Discourse.enable_readonly_mode(Discourse::PG_READONLY_MODE_KEY)
         fallback_handler.verify_master
-
-        connection = postgresql_connection(config.dup.merge(
-          host: config[:replica_host],
-          port: config[:replica_port]
-        ))
-
-        verify_replica(connection)
+        connection = replica_postgresql_connection(config)
       else
         begin
           connection = postgresql_connection(config)
@@ -158,10 +152,21 @@ module ActiveRecord
       connection
     end
 
+    def replica_postgresql_connection(config)
+      config = config.dup.merge(
+        host: config[:replica_host],
+        port: config[:replica_port]
+      )
+
+      connection = postgresql_connection(config)
+      verify_replica(connection)
+      connection
+    end
+
     private
 
     def verify_replica(connection)
-      value = connection.raw_connection.exec("SELECT pg_is_in_recovery()").values[0][0]
+      value = connection.exec_query("SELECT pg_is_in_recovery()").rows[0][0]
       raise "Replica database server is not in recovery mode." if !value
     end
   end

spec/components/active_record/connection_adapters/postgresql_fallback_adapter_spec.rb

@@ -6,11 +6,11 @@ describe ActiveRecord::ConnectionHandling do
   let(:replica_port) { 6432 }
 
   let(:config) do
-    ActiveRecord::Base.configurations[Rails.env].merge(
-      "adapter" => "postgresql_fallback",
-      "replica_host" => replica_host,
-      "replica_port" => replica_port
-    ).symbolize_keys!
+    ActiveRecord::Base.connection_config.merge(
+      adapter: "postgresql_fallback",
+      replica_host: replica_host,
+      replica_port: replica_port
+    )
   end
 
   let(:multisite_db) { "database_2" }
@@ -27,7 +27,6 @@ describe ActiveRecord::ConnectionHandling do
   let(:postgresql_fallback_handler) { PostgreSQLFallbackHandler.instance }
 
   before do
-    skip("Disable these tests until we figure out what is leaking connections")
     postgresql_fallback_handler.initialized = true
 
     ['default', multisite_db].each do |db|
@@ -48,6 +47,7 @@ describe ActiveRecord::ConnectionHandling do
 
     context 'when master server is down' do
       before do
+        skip("Figure out why this test leaks connections")
         @replica_connection = mock('replica_connection')
       end
 
@@ -70,8 +70,8 @@ describe ActiveRecord::ConnectionHandling do
           ActiveRecord::Base.expects(:postgresql_connection).with(configuration).raises(PG::ConnectionBad)
           ActiveRecord::Base.expects(:verify_replica).with(@replica_connection)
 
-          ActiveRecord::Base.expects(:postgresql_connection).with(configuration.merge(
-            host: replica_host, port: replica_port)
+          ActiveRecord::Base.expects(:postgresql_connection).with(
+            configuration.dup.merge(host: replica_host, port: replica_port)
           ).returns(@replica_connection)
         end
 
@@ -129,10 +129,9 @@ describe ActiveRecord::ConnectionHandling do
       it 'should raise the right error' do
         ActiveRecord::Base.expects(:postgresql_connection).with(config).raises(PG::ConnectionBad)
 
-        ActiveRecord::Base.expects(:postgresql_connection).with(config.dup.merge(
-          host: replica_host,
-          port: replica_port
-        )).raises(PG::ConnectionBad).once
+        ActiveRecord::Base.expects(:postgresql_connection).with(
+          config.dup.merge(host: replica_host, port: replica_port)
+        ).raises(PG::ConnectionBad).once
 
         postgresql_fallback_handler.expects(:verify_master).twice