package org.apache.cassandra.triggers; /* * * 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. * */ import java.nio.ByteBuffer; import java.util.Collection; import org.apache.cassandra.db.ColumnFamily; import org.apache.cassandra.db.RowMutation; /** * Trigger interface, For every Mutation received by the coordinator {@link #augment(ByteBuffer, ColumnFamily)} * is called.<p> * * <b> Contract:</b><br> * 1) Implementation of this interface should only have a constructor without parameters <br> * 2) ITrigger implementation can be instantiated multiple times during the server life time. * (Depends on the number of times trigger folder is updated.)<br> * 3) ITrigger implementation should be state-less (avoid dependency on instance variables).<br> * * <br><b>The API is still beta and can change.</b> */ public interface ITrigger { /** * Called exactly once per CF update, returned mutations are atomically updated. * * @param key - Row Key for the update. * @param update - Update received for the CF * @return modifications to be applied, null if no action to be performed. */ public Collection<RowMutation> augment(ByteBuffer key, ColumnFamily update); }