storm-client/src/jvm/org/apache/storm/state/State.java

/**
 * 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.storm.state;

import org.apache.storm.topology.IStatefulBolt;

/**
 * The state of the component that is either managed by the framework (e.g in case of {@link IStatefulBolt}) or managed by the the
 * individual components themselves.
 */
public interface State {
    /**
     * Invoked by the framework to prepare a transaction for commit. It should be possible to commit the prepared state later.
     * <p>
     * The same txid can be prepared again, but the next txid cannot be prepared when previous one is not yet committed.
     * </p>
     *
     * @param txid the transaction id
     */
    void prepareCommit(long txid);

    /**
     * Commit a previously prepared transaction. It should be possible to retrieve a committed state later.
     *
     * @param txid the transaction id
     */
    void commit(long txid);

    /**
     * Persist the current state. This is used when the component manages the state.
     */
    void commit();

    /**
     * Rollback a prepared transaction to the previously committed state.
     */
    void rollback();
}