Add SQL replay checkpoint object to SQL (#868)

* Add SQL replay checkpoint object to Datastore

This will be part of the asynchronous commit-log replay to SQL. Whenever
we successfully export commits up to a particular time, we should
persist that time so we don't replay the same commits again (it is not
idempotent)

* Move SqlReplayCheckpoint from DS to SQL

* Responses to CR

core/src/test/java/google/registry/model/server/ServerSecretTest.java

@@ -15,15 +15,11 @@
 package google.registry.model.server;
 
 import static com.google.common.truth.Truth.assertThat;
-import static google.registry.model.common.CrossTldSingleton.SINGLETON_ID;
-import static google.registry.model.common.EntityGroupRoot.getCrossTldKey;
 import static google.registry.model.ofy.ObjectifyService.ofy;
 import static google.registry.persistence.transaction.TransactionManagerFactory.jpaTm;
 
-import com.googlecode.objectify.Key;
 import google.registry.model.EntityTestCase;
 import google.registry.model.ofy.RequestCapturingAsyncDatastoreService;
-import google.registry.persistence.VKey;
 import java.util.UUID;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -85,11 +81,4 @@ public class ServerSecretTest extends EntityTestCase {
                     .findFirst()
                     .get());
   }
-
-  private static VKey<ServerSecret> createKey() {
-    return VKey.create(
-        ServerSecret.class,
-        SINGLETON_ID,
-        Key.create(getCrossTldKey(), ServerSecret.class, SINGLETON_ID));
-  }
 }

core/src/test/java/google/registry/schema/integration/SqlIntegrationTestSuite.java

@@ -40,6 +40,7 @@ import google.registry.schema.cursor.CursorDaoTest;
 import google.registry.schema.integration.SqlIntegrationTestSuite.AfterSuiteTest;
 import google.registry.schema.integration.SqlIntegrationTestSuite.BeforeSuiteTest;
 import google.registry.schema.registrar.RegistrarDaoTest;
+import google.registry.schema.replay.SqlReplayCheckpointTest;
 import google.registry.schema.server.LockDaoTest;
 import google.registry.schema.tld.PremiumListDaoTest;
 import google.registry.testing.AppEngineExtension;
@@ -100,6 +101,7 @@ import org.junit.runner.RunWith;
   ServerSecretTest.class,
   SignedMarkRevocationListDaoTest.class,
   Spec11ThreatMatchTest.class,
+  SqlReplayCheckpointTest.class,
   TmchCrlTest.class,
   // AfterSuiteTest must be the last entry. See class javadoc for details.
   AfterSuiteTest.class

core/src/test/java/google/registry/schema/replay/SqlReplayCheckpointTest.java

@@ -0,0 +1,61 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.schema.replay;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.persistence.transaction.TransactionManagerFactory.jpaTm;
+import static google.registry.util.DateTimeUtils.START_OF_TIME;
+
+import google.registry.model.EntityTestCase;
+import org.joda.time.DateTime;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link SqlReplayCheckpoint}. */
+public class SqlReplayCheckpointTest extends EntityTestCase {
+
+  SqlReplayCheckpointTest() {
+    super(JpaEntityCoverageCheck.ENABLED);
+  }
+
+  @Test
+  void testEmpty_startOfTime() {
+    assertThat(jpaTm().transact(SqlReplayCheckpoint::get)).isEqualTo(START_OF_TIME);
+  }
+
+  @Test
+  void testSuccess_writes() {
+    DateTime dateTime = DateTime.parse("2012-02-29T00:00:00Z");
+    jpaTm().transact(() -> SqlReplayCheckpoint.set(dateTime));
+    assertThat(jpaTm().transact(SqlReplayCheckpoint::get)).isEqualTo(dateTime);
+  }
+
+  @Test
+  void testSuccess_multipleWrites() {
+    DateTime firstTime = DateTime.parse("2012-02-29T00:00:00Z");
+    jpaTm().transact(() -> SqlReplayCheckpoint.set(firstTime));
+    DateTime secondTime = DateTime.parse("2013-02-28T00:00:00Z");
+    jpaTm().transact(() -> SqlReplayCheckpoint.set(secondTime));
+    assertThat(jpaTm().transact(SqlReplayCheckpoint::get)).isEqualTo(secondTime);
+    jpaTm()
+        .transact(
+            () ->
+                assertThat(
+                        jpaTm()
+                            .getEntityManager()
+                            .createQuery("SELECT COUNT(*) FROM SqlReplayCheckpoint", Long.class)
+                            .getSingleResult())
+                    .isEqualTo(1L));
+  }
+}

core/src/test/java/google/registry/tools/DedupeRecurringBillingEventIdsCommandTest.java

@@ -221,12 +221,6 @@ class DedupeRecurringBillingEventIdsCommandTest
     }
   }
 
-  private static void assertNotChangeInDatastore(ImmutableObject... entities) {
-    for (ImmutableObject entity : entities) {
-      assertThat(ofy().load().entity(entity).now()).isEqualTo(entity);
-    }
-  }
-
   private static void assertNotChangeExceptUpdateTime(ImmutableObject... entities) {
     for (ImmutableObject entity : entities) {
       assertAboutImmutableObjects()