Use cursor to track updating of registrar sheet

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=138221931

java/google/registry/config/ConfigModule.java

@@ -618,17 +618,6 @@ public final class ConfigModule {
     }
   }
 
-  /**
-   * Amount of time between synchronizations of the Registrar spreadsheet.
-   *
-   * @see google.registry.export.sheet.SyncRegistrarsSheetAction
-   */
-  @Provides
-  @Config("sheetRegistrarInterval")
-  public static Duration provideSheetRegistrarInterval() {
-    return Duration.standardHours(1);
-  }
-
   /**
    * Returns SSH client connection and read timeout.
    *

java/google/registry/export/sheet/BUILD

@@ -21,6 +21,7 @@ java_library(
         "//third_party/java/joda_time",
         "//third_party/java/jsr305_annotations",
         "//third_party/java/jsr330_inject",
+        "//third_party/java/objectify:objectify-v4_1",
         "//third_party/java/servlet/servlet_api",
         "//java/google/registry/config",
         "//java/google/registry/model",

java/google/registry/export/sheet/SyncRegistrarsSheet.java

@@ -15,6 +15,8 @@
 package google.registry.export.sheet;
 
 import static com.google.common.base.MoreObjects.firstNonNull;
+import static google.registry.model.common.Cursor.CursorType.SYNC_REGISTRAR_SHEET;
+import static google.registry.model.ofy.ObjectifyService.ofy;
 import static google.registry.model.registrar.RegistrarContact.Type.ABUSE;
 import static google.registry.model.registrar.RegistrarContact.Type.ADMIN;
 import static google.registry.model.registrar.RegistrarContact.Type.BILLING;
@@ -22,6 +24,7 @@ import static google.registry.model.registrar.RegistrarContact.Type.LEGAL;
 import static google.registry.model.registrar.RegistrarContact.Type.MARKETING;
 import static google.registry.model.registrar.RegistrarContact.Type.TECH;
 import static google.registry.model.registrar.RegistrarContact.Type.WHOIS;
+import static google.registry.util.DateTimeUtils.START_OF_TIME;
 
 import com.google.common.base.Function;
 import com.google.common.base.Joiner;
@@ -32,6 +35,8 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Ordering;
 import com.google.gdata.util.ServiceException;
+import com.googlecode.objectify.VoidWork;
+import google.registry.model.common.Cursor;
 import google.registry.model.registrar.Registrar;
 import google.registry.model.registrar.RegistrarAddress;
 import google.registry.model.registrar.RegistrarContact;
@@ -41,10 +46,9 @@ import java.io.IOException;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 import org.joda.time.DateTime;
-import org.joda.time.Duration;
 
 /**
- * Class for synchronizing all {@link Registrar} datastore objects to a Google Spreadsheet.
+ * Class for synchronizing all {@link Registrar} Datastore objects to a Google Spreadsheet.
  *
  * @see SyncRegistrarsSheetAction
  */
@@ -54,11 +58,15 @@ class SyncRegistrarsSheet {
   @Inject SheetSynchronizer sheetSynchronizer;
   @Inject SyncRegistrarsSheet() {}
 
-  /** Returns true if a {@link Registrar} entity was modified in past {@code duration}. */
-  boolean wasRegistrarsModifiedInLast(Duration duration) {
-    DateTime watermark = clock.nowUtc().minus(duration);
+  /**
+   * Returns true if any {@link Registrar} entity was modified since the last time this task
+   * successfully completed, as measured by a cursor.
+   */
+  boolean wereRegistrarsModified() {
+    Cursor cursor = ofy().load().key(Cursor.createGlobalKey(SYNC_REGISTRAR_SHEET)).now();
+    DateTime lastUpdateTime = (cursor == null) ? START_OF_TIME : cursor.getCursorTime();
     for (Registrar registrar : Registrar.loadAll()) {
-      if (DateTimeUtils.isAtOrAfter(registrar.getLastUpdateTime(), watermark)) {
+      if (DateTimeUtils.isAtOrAfter(registrar.getLastUpdateTime(), lastUpdateTime)) {
         return true;
       }
     }
@@ -67,6 +75,7 @@ class SyncRegistrarsSheet {
 
   /** Performs the synchronization operation. */
   void run(String spreadsheetId) throws IOException, ServiceException {
+    final DateTime executionTime = clock.nowUtc();
     sheetSynchronizer.synchronize(
         spreadsheetId,
         FluentIterable
@@ -167,6 +176,11 @@ class SyncRegistrarsSheet {
                   }
                 })
             .toList());
+    ofy().transact(new VoidWork() {
+      @Override
+      public void vrun() {
+        ofy().save().entity(Cursor.createGlobal(SYNC_REGISTRAR_SHEET, executionTime));
+      }});
   }
 
   private static String convertContacts(

java/google/registry/export/sheet/SyncRegistrarsSheetAction.java

@@ -111,7 +111,6 @@ public class SyncRegistrarsSheetAction implements Runnable {
   @Inject SyncRegistrarsSheet syncRegistrarsSheet;
   @Inject @Config("sheetLockTimeout") Duration timeout;
   @Inject @Config("sheetRegistrarId") Optional<String> idConfig;
-  @Inject @Config("sheetRegistrarInterval") Duration interval;
   @Inject @Parameter("id") Optional<String> idParam;
   @Inject SyncRegistrarsSheetAction() {}
 
@@ -123,8 +122,7 @@ public class SyncRegistrarsSheetAction implements Runnable {
       return;
     }
     if (!idParam.isPresent()) {
-      // TODO(b/19082368): Use a cursor.
-      if (!syncRegistrarsSheet.wasRegistrarsModifiedInLast(interval)) {
+      if (!syncRegistrarsSheet.wereRegistrarsModified()) {
         Result.NOTMODIFIED.send(response, null);
         return;
       }

java/google/registry/model/common/Cursor.java

@@ -71,7 +71,14 @@ public class Cursor extends ImmutableObject {
      * for which Recurring billing events have been expanded (i.e. the inclusive first billing time
      * for the next expansion job).
      */
-    RECURRING_BILLING(EntityGroupRoot.class);
+    RECURRING_BILLING(EntityGroupRoot.class),
+
+    /**
+     * Cursor for {@link google.registry.export.sheet.SyncRegistrarsSheetAction}. The DateTime
+     * stored is the last time that registrar changes were successfully synced to the sheet. If
+     * there were no changes since the last time the action run, the cursor is not updated.
+     */
+    SYNC_REGISTRAR_SHEET(EntityGroupRoot.class);
 
     /** See the definition of scope on {@link #getScopeClass}. */
     private final Class<? extends ImmutableObject> scope;