org.apache.nifi.migration.RelationshipConfiguration Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.nifi.migration;
import org.apache.nifi.processor.Relationship;
/**
*
* RelationshipConfiguration can be used to convey how a Processor's configuration should be migrated from an old configuration
* to the latest configuration. This provides the ability to split a single Relationship into multiple, or to rename Relationships.
*
*
* Note that it does not provide for the ability to merge multiple Relationships into a single Relationship, as doing so would cause unexpected
* data duplication. Consider, for example, that a Processor has two Connections. The first has Relationship A while the second has Relationship B.
* If we allows A and B to be merged together into C, anything that gets transferred to C would now need to go to both of those Connections, creating
* data duplication.
*
*
* Additionally, there is no option to remove a Relationship. This is because if a Relationship is to be removed, it can be simply dropped from the Processor.
* Any existing connection that has that Relationship will be "ghosted" in the UI to show the user that it's no longer supported, but NiFi and the Processor
* will continue to behave as expected.
*
*/
public interface RelationshipConfiguration {
/**
* Changes the Relationship from the given older name to the updated name
* @param relationshipName the old name of the relationship
* @param newName the new name to use
* @return true if the Relationship is renamed, false if the given Relationship does not exist
* @throws IllegalStateException if both the relationship name and the new name already are defined as relationships
*/
boolean renameRelationship(String relationshipName, String newName);
/**
*
* Splits the given Relationship into multiple new relationships. Each connection that has the Relationship as a selected Relationship will be updated to
* have all of the new Relationships as selected relationships instead. If the existing Relationship is auto-terminated, all of the newly defined ones
* will be as well. If the existing Relationship is auto-retried, so will be the new Relationships.
*
*
*
* It is possible to split an existing relationship into the same relationship and additional relationships. For example, it is
* valid to call this method as:
*
*
* relationshipConfiguration.splitRelationship("A", "A", "B", "C");
*
*
*
* In order to split the "A" relationship into three relationships: "A", "B", and "C". However, upon restart, NiFi will have already split the "A"
* relationship into three. So relationships "B" and "C" will already exist, resulting in an {@code IllegalStateException}. Therefore, if splitting
* a relationship into multiple that include the original relationship, it is important to guard against this by checking of the new relationships
* exist first:
*
*
*
* if (!relationshipConfiguration.hasRelationship("B")) {
* relationshipConfiguration.splitRelationship("A", "A", "B", "C");
* }
*
*
*
* This ensures that we do not attempt to split relationship "A" if it has already been done.
*
*
* @param relationshipName the name of the existing relationship
* @param newRelationshipName the first of the new relationship names
* @param additionalRelationshipNames additional names for the new relationship
* @return true if the Relationship is split, false if the given Relationship does not exist
* @throws IllegalStateException if the given relationship name exists and one of the given new relationships already exists
*/
boolean splitRelationship(String relationshipName, String newRelationshipName, String... additionalRelationshipNames);
/**
* Indicates whether or not the relationship with the given name exists in the configuration
* @param relationshipName the name of the relationship
* @return true if the relationship exists, false if the relationship is not known
*/
boolean hasRelationship(String relationshipName);
/**
* Indicates whether or not the relationship with the given name exists in the configuration
* @param relationship the relationship to check
* @return true if the relationship exists, false if the relationship is not known
*/
default boolean hasRelationship(Relationship relationship) {
return hasRelationship(relationship.getName());
}
}