Enrich validate nested mappings (#42452)

Ensures that fields retained in an enrich index from a source are not contained
under a nested field. It additionally makes sure that key fields exist, and that
value fields are checked if they are present. The policy runner test has also
been expanded with some faulty mapping test cases.

x-pack/plugin/enrich/src/main/java/org/elasticsearch/xpack/enrich/EnrichPolicyRunner.java

@@ -33,6 +33,7 @@ import org.elasticsearch.cluster.metadata.AliasMetaData;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.metadata.MappingMetaData;
 import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.collect.ImmutableOpenMap;
 import org.elasticsearch.common.settings.Settings;
@@ -99,6 +100,11 @@ public class EnrichPolicyRunner implements Runnable {
     private Map<String, Object> getMappings(final GetIndexResponse getIndexResponse, final String sourceIndexName) {
         ImmutableOpenMap<String, ImmutableOpenMap<String, MappingMetaData>> mappings = getIndexResponse.mappings();
         ImmutableOpenMap<String, MappingMetaData> indexMapping = mappings.get(sourceIndexName);
+        if (indexMapping.keys().size() == 0) {
+            throw new ElasticsearchException(
+                "Enrich policy execution for [{}] failed. No mapping available on source [{}] included in [{}]",
+                policyName, sourceIndexName, policy.getIndices());
+        }
         assert indexMapping.keys().size() == 1 : "Expecting only one type per index";
         MappingMetaData typeMapping = indexMapping.iterator().next().value;
         return typeMapping.sourceAsMap();
@@ -109,22 +115,77 @@ public class EnrichPolicyRunner implements Runnable {
         logger.debug("Policy [{}]: Validating [{}] source mappings", policyName, sourceIndices);
         for (String sourceIndex : sourceIndices) {
             Map<String, Object> mapping = getMappings(getIndexResponse, sourceIndex);
-            Map<?, ?> properties = ((Map<?, ?>) mapping.get("properties"));
-            if (properties == null) {
-                listener.onFailure(
-                    new ElasticsearchException(
-                        "Enrich policy execution for [{}] failed. Could not read mapping for source [{}] included by pattern [{}]",
-                        policyName, sourceIndex, policy.getIndices()));
+            // First ensure mapping is set
+            if (mapping.get("properties") == null) {
+                throw new ElasticsearchException(
+                    "Enrich policy execution for [{}] failed. Could not read mapping for source [{}] included by pattern [{}]",
+                    policyName, sourceIndex, policy.getIndices());
             }
-            if (properties.containsKey(policy.getEnrichKey()) == false) {
-                listener.onFailure(
-                    new ElasticsearchException(
-                        "Enrich policy execution for [{}] failed. Could not locate enrich key field [{}] on mapping for index [{}]",
-                        policyName, policy.getEnrichKey(), sourceIndex));
+            // Validate the key and values
+            try {
+                validateField(mapping, policy.getEnrichKey(), true);
+                for (String valueFieldName : policy.getEnrichValues()) {
+                    validateField(mapping, valueFieldName, false);
+                }
+            } catch (ElasticsearchException e) {
+                throw new ElasticsearchException(
+                        "Enrich policy execution for [{}] failed while validating field mappings for index [{}]",
+                        e, policyName, sourceIndex);
             }
         }
     }
 
+    private void validateField(Map<?, ?> properties, String fieldName, boolean fieldRequired) {
+        assert Strings.isEmpty(fieldName) == false: "Field name cannot be null or empty";
+        String[] fieldParts = fieldName.split("\\.");
+        StringBuilder parent = new StringBuilder();
+        Map<?, ?> currentField = properties;
+        boolean onRoot = true;
+        for (String fieldPart : fieldParts) {
+            // Ensure that the current field is of object type only (not a nested type or a non compound field)
+            Object type = currentField.get("type");
+            if (type != null && "object".equals(type) == false) {
+                throw new ElasticsearchException(
+                    "Could not traverse mapping to field [{}]. The [{}] field must be regular object but was [{}].",
+                    fieldName,
+                    onRoot ? "root" : parent.toString(),
+                    type
+                );
+            }
+            Map<?, ?> currentProperties = ((Map<?, ?>) currentField.get("properties"));
+            if (currentProperties == null) {
+                if (fieldRequired) {
+                    throw new ElasticsearchException(
+                        "Could not traverse mapping to field [{}]. Expected the [{}] field to have sub fields but none were configured.",
+                        fieldName,
+                        onRoot ? "root" : parent.toString()
+                    );
+                } else {
+                    return;
+                }
+            }
+            currentField = ((Map<?, ?>) currentProperties.get(fieldPart));
+            if (currentField == null) {
+                if (fieldRequired) {
+                    throw new ElasticsearchException(
+                        "Could not traverse mapping to field [{}]. Could not find the [{}] field under [{}]",
+                        fieldName,
+                        fieldPart,
+                        onRoot ? "root" : parent.toString()
+                    );
+                } else {
+                    return;
+                }
+            }
+            if (onRoot) {
+               onRoot = false;
+            } else {
+                parent.append(".");
+            }
+            parent.append(fieldPart);
+        }
+    }
+
     private XContentBuilder resolveEnrichMapping(final EnrichPolicy policy) {
         // Currently the only supported policy type is EnrichPolicy.EXACT_MATCH_TYPE, which is a keyword type
         String keyType;