Add a test of the new behavior

Author: joegallo

modules/ingest-geoip/src/test/java/org/elasticsearch/ingest/geoip/GeoIpProcessorFactoryTests.java

@@ -549,6 +549,7 @@ public void testDatabaseNotReadyYet() throws Exception {
             Map<String, Object> config = new HashMap<>();
             config.put("field", "source_field");
             config.put("database_file", "GeoLite2-City.mmdb");
+            config.put("ignore_missing", true);
 
             GeoIpProcessor.DatabaseUnavailableProcessor processor = (GeoIpProcessor.DatabaseUnavailableProcessor) factory.create(
                 null,
@@ -565,6 +566,13 @@ public void testDatabaseNotReadyYet() throws Exception {
                 assertThat(document.getSourceAndMetadata().get("geoip"), nullValue());
                 assertThat(document.getSourceAndMetadata().get("tags"), equalTo(List.of("_geoip_database_unavailable_GeoLite2-City.mmdb")));
             }
+            {
+                // if there's no value for the source_field and ignore_missing is true, then we don't tag the document
+                document = RandomDocumentPicks.randomIngestDocument(random(), new HashMap<>()); // note: no source_field
+                processor.execute(document);
+                assertThat(document.getSourceAndMetadata().get("geoip"), nullValue());
+                assertThat(document.getSourceAndMetadata().get("tags"), nullValue());
+            }
         }
 
         copyDatabase("GeoLite2-City-Test.mmdb", geoipTmpDir);