[Transform] Feature Flag for CPS (elastic#141182)

Moving Transform's CPS features behind a feature flag, enabling it for
snapshot builds but leaving it disabled for release builds.

Author: prwhelan

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfig.java

@@ -13,8 +13,11 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.util.FeatureFlag;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.search.crossproject.CrossProjectModeDecider;
+import org.elasticsearch.transport.RemoteClusterAware;
 import org.elasticsearch.xcontent.ConstructingObjectParser;
 import org.elasticsearch.xcontent.NamedXContentRegistry;
 import org.elasticsearch.xcontent.ObjectParser;
@@ -44,6 +47,7 @@
 import java.util.Map;
 import java.util.Objects;
 
+import static org.elasticsearch.action.ValidateActions.addValidationError;
 import static org.elasticsearch.xcontent.ConstructingObjectParser.constructorArg;
 import static org.elasticsearch.xcontent.ConstructingObjectParser.optionalConstructorArg;
 
@@ -61,6 +65,8 @@ public final class TransformConfig implements SimpleDiffable<TransformConfig>, W
     public static final String NAME = "data_frame_transform_config";
     public static final ParseField HEADERS = new ParseField("headers");
 
+    public static final FeatureFlag TRANSFORM_CROSS_PROJECT = new FeatureFlag("transform_cross_project");
+
     /** Specifies all the possible transform functions. */
     public enum Function {
         PIVOT,
@@ -355,6 +361,36 @@ public ActionRequestValidationException validate(ActionRequestValidationExceptio
         return validationException;
     }
 
+    public ActionRequestValidationException validateNoCrossProjectWhenCrossProjectIsDisabled(
+        CrossProjectModeDecider crossProjectModeDecider,
+        ActionRequestValidationException validationException
+    ) {
+        if (crossProjectModeDecider.crossProjectEnabled()) {
+            return validateNoCrossProjectWhenCrossProjectFeatureIsDisabled(TRANSFORM_CROSS_PROJECT.isEnabled(), validationException);
+        }
+        return validationException;
+    }
+
+    // visible for testing
+    // remove both this and validateNoCrossProjectWhenCrossProjectIsDisabled when the feature is launched
+    ActionRequestValidationException validateNoCrossProjectWhenCrossProjectFeatureIsDisabled(
+        boolean featureEnabled,
+        ActionRequestValidationException validationException
+    ) {
+        if (featureEnabled == false) {
+            // verify there are no remote indices
+            var indices = getSource().getIndex();
+            var remoteIndices = RemoteClusterAware.getRemoteIndexExpressions(indices);
+            if (remoteIndices.isEmpty() == false) {
+                validationException = addValidationError(
+                    "Cross-project calls are not supported, but remote indices were requested: " + remoteIndices,
+                    validationException
+                );
+            }
+        }
+        return validationException;
+    }
+
     /**
      * Parses the transform configuration for deprecations
      *

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfigTests.java

@@ -13,9 +13,11 @@
 import org.elasticsearch.common.io.stream.NamedWriteableAwareStreamInput;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.Writeable.Reader;
+import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.core.Tuple;
+import org.elasticsearch.search.crossproject.CrossProjectModeDecider;
 import org.elasticsearch.xcontent.ToXContent;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentFactory;
@@ -45,6 +47,7 @@
 import static org.elasticsearch.xpack.core.transform.transforms.SourceConfigTests.randomInvalidSourceConfig;
 import static org.elasticsearch.xpack.core.transform.transforms.SourceConfigTests.randomSourceConfig;
 import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
@@ -1048,6 +1051,98 @@ public void testSerializingMetadataPreservesOrder() throws IOException {
         assertThat(new ArrayList<>(transformConfig.getMetadata().keySet()), is(equalTo(List.of("d", "a", "c", "e", "b"))));
     }
 
+    public void testCrossProjectWithFeatureEnabled() throws IOException {
+        var transformConfig = createTransformConfigFromString("""
+            {
+              "source": {
+                "index": "project-1:src"
+              },
+              "dest": {
+                "index": "dest"
+              },
+              "pivot": {
+                "group_by": {
+                  "id": {
+                    "terms": {
+                      "field": "id"
+                    }
+                  }
+                },
+                "aggs": {
+                  "avg": {
+                    "avg": {
+                      "field": "points"
+                    }
+                  }
+                }
+              }
+            }""", "cross-project-feature-enabled");
+        assertNull(transformConfig.validateNoCrossProjectWhenCrossProjectFeatureIsDisabled(true, null));
+    }
+
+    public void testCrossProjectWithFeatureDisabled() throws IOException {
+        var transformConfig = createTransformConfigFromString("""
+            {
+              "source": {
+                "index": "project-1:src"
+              },
+              "dest": {
+                "index": "dest"
+              },
+              "pivot": {
+                "group_by": {
+                  "id": {
+                    "terms": {
+                      "field": "id"
+                    }
+                  }
+                },
+                "aggs": {
+                  "avg": {
+                    "avg": {
+                      "field": "points"
+                    }
+                  }
+                }
+              }
+            }""", "cross-project-feature-not-enabled");
+        var validationException = transformConfig.validateNoCrossProjectWhenCrossProjectFeatureIsDisabled(false, null);
+        assertNotNull(validationException);
+        assertThat(
+            validationException.getMessage(),
+            containsString("Cross-project calls are not supported, but remote indices were requested: [project-1:src]")
+        );
+    }
+
+    public void testNotCrossProjectEnvironment() throws IOException {
+        var transformConfig = createTransformConfigFromString("""
+            {
+              "source": {
+                "index": "remote-1:src"
+              },
+              "dest": {
+                "index": "dest"
+              },
+              "pivot": {
+                "group_by": {
+                  "id": {
+                    "terms": {
+                      "field": "id"
+                    }
+                  }
+                },
+                "aggs": {
+                  "avg": {
+                    "avg": {
+                      "field": "points"
+                    }
+                  }
+                }
+              }
+            }""", "cross-project");
+        assertNull(transformConfig.validateNoCrossProjectWhenCrossProjectIsDisabled(new CrossProjectModeDecider(Settings.EMPTY), null));
+    }
+
     private TransformConfig createTransformConfigFromString(String json, String id) throws IOException {
         return createTransformConfigFromString(json, id, false);
     }

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/transforms/TransformPersistentTasksExecutor.java

@@ -26,7 +26,6 @@
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Randomness;
-import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.Strings;
@@ -351,7 +350,15 @@ protected void nodeOperation(AllocatedPersistentTask task, @Nullable TransformTa
                 return;
             }
 
-            ValidationException validationException = config.validate(null);
+            var validationException = config.validate(null);
+
+            // if we had created a transform when the feature flag was enabled, but we disabled the feature flag
+            // then verify that this transform does not use CPS features
+            validationException = config.validateNoCrossProjectWhenCrossProjectIsDisabled(
+                transformServices.crossProjectModeDecider(),
+                validationException
+            );
+
             if (validationException == null) {
                 indexerBuilder.setTransformConfig(config);
                 transformServices.configManager().getTransformStoredDoc(transformId, false, l);