Move while_preventing_writes from conn to handler

If we put the `while_preventing_writes` on the connection then the
middleware that sends reads to the primary and ensures they can't write
will not work. The `while_preventing_writes` will only be applied to the
connection which it's called on - which in the case of the middleware is
Ar::Base.

This worked fine if you called it directly like
`OtherDbConn.connection.while_preventing_writes` but Rails didn't have a
way of knowing you wanted to call it on all the connections.

The change here moves the `while_preventing_writes` method from the
connection to the handler so that it can block writes to all queries for
that handler. This will apply to all the connections associated with
that handler.

3 files changed, 25 insertions, 21 deletions

diff --git a/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb b/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
index 9364fabb35..e1f7a0b7c5 100644
--- a/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
@@ -8,6 +8,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
 
   def setup
     @conn = ActiveRecord::Base.connection
+    @connection_handler = ActiveRecord::Base.connection_handler
   end
 
   def test_exec_query_nothing_raises_with_no_result_queries
@@ -148,7 +149,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
 
   def test_errors_when_an_insert_query_is_called_while_preventing_writes
     assert_raises(ActiveRecord::ReadOnlyError) do
-      @conn.while_preventing_writes do
+      @connection_handler.while_preventing_writes do
         @conn.insert("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
       end
     end
@@ -158,7 +159,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
     @conn.insert("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
 
     assert_raises(ActiveRecord::ReadOnlyError) do
-      @conn.while_preventing_writes do
+      @connection_handler.while_preventing_writes do
         @conn.update("UPDATE `engines` SET `engines`.`car_id` = '9989' WHERE `engines`.`car_id` = '138853948594'")
       end
     end
@@ -168,7 +169,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
     @conn.execute("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
 
     assert_raises(ActiveRecord::ReadOnlyError) do
-      @conn.while_preventing_writes do
+      @connection_handler.while_preventing_writes do
         @conn.execute("DELETE FROM `engines` where `engines`.`car_id` = '138853948594'")
       end
     end
@@ -178,7 +179,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
     @conn.execute("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
 
     assert_raises(ActiveRecord::ReadOnlyError) do
-      @conn.while_preventing_writes do
+      @connection_handler.while_preventing_writes do
         @conn.execute("REPLACE INTO `engines` SET `engines`.`car_id` = '249823948'")
       end
     end
@@ -187,19 +188,19 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
   def test_doesnt_error_when_a_select_query_is_called_while_preventing_writes
     @conn.execute("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
 
-    @conn.while_preventing_writes do
+    @connection_handler.while_preventing_writes do
       assert_equal 1, @conn.execute("SELECT `engines`.* FROM `engines` WHERE `engines`.`car_id` = '138853948594'").entries.count
     end
   end
 
   def test_doesnt_error_when_a_show_query_is_called_while_preventing_writes
-    @conn.while_preventing_writes do
+    @connection_handler.while_preventing_writes do
       assert_equal 2, @conn.execute("SHOW FULL FIELDS FROM `engines`").entries.count
     end
   end
 
   def test_doesnt_error_when_a_set_query_is_called_while_preventing_writes
-    @conn.while_preventing_writes do
+    @connection_handler.while_preventing_writes do
       assert_nil @conn.execute("SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci")
     end
   end
@@ -207,7 +208,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
   def test_doesnt_error_when_a_read_query_with_leading_chars_is_called_while_preventing_writes
     @conn.execute("INSERT INTO `engines` (`car_id`) VALUES ('138853948594')")
 
-    @conn.while_preventing_writes do
+    @connection_handler.while_preventing_writes do
       assert_equal 1, @conn.execute("(\n( SELECT `engines`.* FROM `engines` WHERE `engines`.`car_id` = '138853948594' ) )").entries.count
     end
   end
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index bc517cef82..68bc87eaf8 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -13,6 +13,7 @@ module ActiveRecord
 
       def setup
         @connection = ActiveRecord::Base.connection
+        @connection_handler = ActiveRecord::Base.connection_handler
       end
 
       def test_bad_connection
@@ -379,7 +380,7 @@ module ActiveRecord
       def test_errors_when_an_insert_query_is_called_while_preventing_writes
         with_example_table do
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @connection.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @connection.execute("INSERT INTO ex (data) VALUES ('138853948594')")
             end
           end
@@ -391,7 +392,7 @@ module ActiveRecord
           @connection.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @connection.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @connection.execute("UPDATE ex SET data = '9989' WHERE data = '138853948594'")
             end
           end
@@ -403,7 +404,7 @@ module ActiveRecord
           @connection.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @connection.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @connection.execute("DELETE FROM ex where data = '138853948594'")
             end
           end
@@ -414,20 +415,20 @@ module ActiveRecord
         with_example_table do
           @connection.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
-          @connection.while_preventing_writes do
+          @connection_handler.while_preventing_writes do
             assert_equal 1, @connection.execute("SELECT * FROM ex WHERE data = '138853948594'").entries.count
           end
         end
       end
 
       def test_doesnt_error_when_a_show_query_is_called_while_preventing_writes
-        @connection.while_preventing_writes do
+        @connection_handler.while_preventing_writes do
           assert_equal 1, @connection.execute("SHOW TIME ZONE").entries.count
         end
       end
 
       def test_doesnt_error_when_a_set_query_is_called_while_preventing_writes
-        @connection.while_preventing_writes do
+        @connection_handler.while_preventing_writes do
           assert_equal [], @connection.execute("SET standard_conforming_strings = on").entries
         end
       end
@@ -436,7 +437,7 @@ module ActiveRecord
         with_example_table do
           @connection.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
-          @connection.while_preventing_writes do
+          @connection_handler.while_preventing_writes do
             assert_equal 1, @connection.execute("(\n( SELECT * FROM ex WHERE data = '138853948594' ) )").entries.count
           end
         end
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index 22dc0eaad2..508f7d8945 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -19,6 +19,8 @@ module ActiveRecord
         @conn = Base.sqlite3_connection database: ":memory:",
                                         adapter: "sqlite3",
                                         timeout: 100
+
+        @connection_handler = ActiveRecord::Base.connection_handler
       end
 
       def test_bad_connection
@@ -572,7 +574,7 @@ module ActiveRecord
       def test_errors_when_an_insert_query_is_called_while_preventing_writes
         with_example_table "id int, data string" do
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @conn.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @conn.execute("INSERT INTO ex (data) VALUES ('138853948594')")
             end
           end
@@ -584,7 +586,7 @@ module ActiveRecord
           @conn.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @conn.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @conn.execute("UPDATE ex SET data = '9989' WHERE data = '138853948594'")
             end
           end
@@ -596,7 +598,7 @@ module ActiveRecord
           @conn.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @conn.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @conn.execute("DELETE FROM ex where data = '138853948594'")
             end
           end
@@ -608,7 +610,7 @@ module ActiveRecord
           @conn.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
           assert_raises(ActiveRecord::ReadOnlyError) do
-            @conn.while_preventing_writes do
+            @connection_handler.while_preventing_writes do
               @conn.execute("REPLACE INTO ex (data) VALUES ('249823948')")
             end
           end
@@ -619,7 +621,7 @@ module ActiveRecord
         with_example_table "id int, data string" do
           @conn.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
-          @conn.while_preventing_writes do
+          @connection_handler.while_preventing_writes do
             assert_equal 1, @conn.execute("SELECT data from ex WHERE data = '138853948594'").count
           end
         end
@@ -629,7 +631,7 @@ module ActiveRecord
         with_example_table "id int, data string" do
           @conn.execute("INSERT INTO ex (data) VALUES ('138853948594')")
 
-          @conn.while_preventing_writes do
+          @connection_handler.while_preventing_writes do
             assert_equal 1, @conn.execute("  SELECT data from ex WHERE data = '138853948594'").count
           end
         end