Properly format IndexGraveyard deletion date as date (#27362)

The toXContent method for IndexGraveYard (which is a collection of tombstones for explicitly marking indices as deleted in the cluster state) confused timeValue with dateField, resulting in output of the form "delete_date" : "23424.3d" instead of "delete_date":"2017-11-13T15:50:51.614Z".

core/src/main/java/org/elasticsearch/cluster/metadata/IndexGraveyard.java

@@ -34,6 +34,8 @@ import org.elasticsearch.common.xcontent.ToXContentObject;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.index.Index;
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeZone;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -432,7 +434,7 @@ public final class IndexGraveyard implements MetaData.Custom {
             builder.startObject();
             builder.field(INDEX_KEY);
             index.toXContent(builder, params);
-            builder.timeValueField(DELETE_DATE_IN_MILLIS_KEY, DELETE_DATE_KEY, deleteDateInMillis, TimeUnit.MILLISECONDS);
+            builder.dateField(DELETE_DATE_IN_MILLIS_KEY, DELETE_DATE_KEY, deleteDateInMillis);
             return builder.endObject();
         }
 

core/src/test/java/org/elasticsearch/cluster/metadata/IndexGraveyardTests.java

@@ -19,6 +19,7 @@
 
 package org.elasticsearch.cluster.metadata;
 
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.UUIDs;
 import org.elasticsearch.common.io.stream.BytesStreamOutput;
 import org.elasticsearch.common.settings.Settings;
@@ -36,6 +37,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.stream.Collectors;
 
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.lessThan;
 import static org.hamcrest.Matchers.not;
@@ -66,6 +68,11 @@ public class IndexGraveyardTests extends ESTestCase {
         builder.startObject();
         graveyard.toXContent(builder, ToXContent.EMPTY_PARAMS);
         builder.endObject();
+        if (graveyard.getTombstones().size() > 0) {
+            // check that date properly printed
+            assertThat(Strings.toString(graveyard, false, true),
+                containsString(XContentBuilder.DEFAULT_DATE_PRINTER.print(graveyard.getTombstones().get(0).getDeleteDateInMillis())));
+        }
         XContentParser parser = createParser(JsonXContent.jsonXContent, builder.bytes());
         parser.nextToken(); // the beginning of the parser
         assertThat(IndexGraveyard.fromXContent(parser), equalTo(graveyard));