system index mapping workaround

Author: ywangd

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/CreateApiKeyRequest.java

@@ -151,8 +151,17 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeOptionalTimeValue(expiration);
         out.writeList(roleDescriptors);
         refreshPolicy.writeTo(out);
-        if (out.getVersion().onOrAfter(Version.V_7_13_0)) {
-            out.writeMap(metadata);
+        if (metadata != null && false == metadata.isEmpty()) {
+            if (out.getVersion().before(Version.V_7_13_0)) {
+                throw new IllegalArgumentException(
+                    "api key metadata requires minimum node version to be [7.13.0], got: [" + out.getVersion() + "]");
+            } else {
+                out.writeMap(metadata);
+            }
+        } else {
+            if (out.getVersion().onOrAfter(Version.V_7_13_0)) {
+                out.writeMap(metadata);
+            }
         }
     }
 }

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/Security.java

@@ -1277,12 +1277,16 @@ private static Settings getIndexSettings() {
     }
 
     private static XContentBuilder getIndexMappings() {
+        return getIndexMappings(Version.CURRENT);
+    }
+
+    public static XContentBuilder getIndexMappings(Version compatibleVersion) {
         try {
             final XContentBuilder builder = jsonBuilder();
             builder.startObject();
             {
                 builder.startObject("_meta");
-                builder.field(SECURITY_VERSION_STRING, Version.CURRENT.toString());
+                builder.field(SECURITY_VERSION_STRING, compatibleVersion.toString());
                 builder.endObject();
 
                 builder.field("dynamic", "strict");
@@ -1332,9 +1336,11 @@ private static XContentBuilder getIndexMappings() {
                     builder.field("dynamic", false);
                     builder.endObject();
 
-                    builder.startObject("metadata_flattened");
-                    builder.field("type", "flattened");
-                    builder.endObject();
+                    if (compatibleVersion.onOrAfter(Version.V_7_13_0)) {
+                        builder.startObject("metadata_flattened");
+                        builder.field("type", "flattened");
+                        builder.endObject();
+                    }
 
                     builder.startObject("enabled");
                     builder.field("type", "boolean");

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/support/SecurityIndexManager.java

@@ -35,6 +35,7 @@
 import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
 import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.gateway.GatewayService;
 import org.elasticsearch.index.Index;
@@ -43,6 +44,7 @@
 import org.elasticsearch.indices.IndexClosedException;
 import org.elasticsearch.indices.SystemIndexDescriptor;
 import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.xpack.security.Security;
 
 import java.time.Instant;
 import java.util.HashSet;
@@ -384,8 +386,16 @@ public void onFailure(Exception e) {
                         indexState.concreteIndexName,
                         systemIndexDescriptor.getAliasName()
                     );
+                    final String mappings;
+                    // Flattened field is available since 7.3.0 and it is used by API key metadata in 7.13.0.
+                    // Therefore if the minimum node version is before 7.3.0, we fallback to use the mapping from 7.12.0.
+                    if (indexState.minimumNodeVersion.before(Version.V_7_3_0)) {
+                        mappings = Strings.toString(Security.getIndexMappings(Version.V_7_12_0));
+                    } else {
+                        mappings = systemIndexDescriptor.getMappings();
+                    }
                     PutMappingRequest request = new PutMappingRequest(indexState.concreteIndexName).source(
-                        systemIndexDescriptor.getMappings(),
+                        mappings,
                         XContentType.JSON
                     ).type(MapperService.SINGLE_MAPPING_NAME).origin(systemIndexDescriptor.getOrigin());
                     executeAsyncWithOrigin(client.threadPool().getThreadContext(), systemIndexDescriptor.getOrigin(), request,