Fix NPE when logging null values in JSON (#53715)

Slow log's routing value when null was causing ESLogMessage.asJson
method to throw Null Pointer Exception. This should be fixed in
ESLogMessage as well as prevent passing that key at all.
This only happens in 8 because of previous refactoring #46702

server/src/main/java/org/elasticsearch/common/logging/ESLogMessage.java

@@ -79,7 +79,7 @@ public class ESLogMessage extends MapMessage<ESLogMessage, Object> {
             StringBuilders.escapeJson(sb, start);
             sb.append(Chars.DQUOTE).append(':').append(Chars.DQUOTE);
             start = sb.length();
-            sb.append(getIndexedReadOnlyStringMap().getValueAt(i).toString());
+            sb.append((Object) getIndexedReadOnlyStringMap().getValueAt(i));
             StringBuilders.escapeJson(sb, start);
             sb.append(Chars.DQUOTE);
         }

server/src/main/java/org/elasticsearch/index/IndexingSlowLog.java

@@ -24,8 +24,8 @@ import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.util.StringBuilders;
 import org.elasticsearch.common.Booleans;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.logging.ESLogMessage;
+import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.unit.TimeValue;
@@ -180,7 +180,9 @@ public final class IndexingSlowLog implements IndexingOperationListener {
             map.put("took", TimeValue.timeValueNanos(tookInNanos));
             map.put("took_millis", ""+TimeUnit.NANOSECONDS.toMillis(tookInNanos));
             map.put("id", doc.id());
-            map.put("routing", doc.routing());
+            if (doc.routing() != null) {
+                map.put("routing", doc.routing());
+            }
 
             if (maxSourceCharsToLog == 0 || doc.source() == null || doc.source().length() == 0) {
                 return map;

server/src/test/java/org/elasticsearch/index/IndexingSlowLogTests.java

@@ -46,6 +46,7 @@ import static org.hamcrest.Matchers.hasToString;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
+import static org.hamcrest.Matchers.nullValue;
 import static org.hamcrest.Matchers.startsWith;
 
 public class IndexingSlowLogTests extends ESTestCase {
@@ -72,6 +73,20 @@ public class IndexingSlowLogTests extends ESTestCase {
         assertThat(p.get("source"), containsString("{\\\"foo\\\":\\\"bar\\\"}"));
     }
 
+    public void testEmptyRoutingField() throws IOException {
+        BytesReference source = BytesReference.bytes(JsonXContent.contentBuilder()
+                                                                 .startObject().field("foo", "bar").endObject());
+        ParsedDocument pd = new ParsedDocument(new NumericDocValuesField("version", 1),
+            SeqNoFieldMapper.SequenceIDFields.emptySeqID(), "id",
+            null, null, source, XContentType.JSON, null);
+        Index index = new Index("foo", "123");
+
+        ESLogMessage p = IndexingSlowLogMessage.of(index, pd, 10, true, 0);
+        assertThat(p.get("routing"), nullValue());
+
+        assertThat(p.asString(), containsString("routing[]"));
+    }
+
     public void testSlowLogParsedDocumentPrinterSourceToLog() throws IOException {
         BytesReference source = BytesReference.bytes(JsonXContent.contentBuilder()
             .startObject().field("foo", "bar").endObject());