tephra-core/src/main/java/org/apache/tephra/persist/TransactionLogWriter.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.tephra.persist;

import java.io.Closeable;
import java.io.IOException;

/**
 * Common interface for transaction log writers used by classes extending {@link AbstractTransactionLog}.
 */
public interface TransactionLogWriter extends Closeable {
  /**
   * Adds a new transaction entry to the log.  Note that this does not guarantee that the entry has been flushed
   * to persistent storage until {@link #sync()} has been called.
   *
   * @param entry The transaction edit to append.
   * @throws IOException If an error occurs while writing the edit to storage.
   */
  void append(AbstractTransactionLog.Entry entry) throws IOException;

  /**
   * Makes an entry of number of transaction entries that will follow in that log in a single sync.
   *
   * @param count Number of transaction entries.
   * @throws IOException If an error occurs while writing the count to storage.
   */
  void commitMarker(int count) throws IOException;

  /**
   * @return the current position in the output.
   */
  long getPosition() throws IOException;

  /**
   * Syncs any pending transaction edits added through {@link #append(AbstractTransactionLog.Entry)},
   * but not yet flushed to durable storage.
   *
   * @throws IOException If an error occurs while flushing the outstanding edits.
   */
  void sync() throws IOException;
}