| /* |
| * 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.reef.io.checkpoint; |
| |
| import java.io.IOException; |
| import java.nio.channels.ReadableByteChannel; |
| import java.nio.channels.WritableByteChannel; |
| |
| /** |
| * The CheckpointService provides a simple API to store and retrieve the state of a task. |
| * <p> |
| * Checkpoints are assumed to be atomic, single-writer, write-once, multiple-readers, ready-many type of objects. |
| * |
| * To ensure this, any implementation of this interface must. |
| * 1) Return a CheckpointID to a client only |
| * upon the successful {@link #commit(CheckpointWriteChannel) commit} of the checkpoint. |
| * 2) Prevent any checkpoint from being re-opened for writes. |
| * <p> |
| * Non-functional properties such as durability, availability, compression, garbage collection, and |
| * quotas are left to the implementation. |
| * <p> |
| * This API is envisioned as the basic building block for a checkpoint service, on top of which richer |
| * interfaces can be layered (e.g., frameworks providing object-serialization, checkpoint metadata and |
| * provenance, etc.) |
| */ |
| public interface CheckpointService { |
| |
| /** |
| * Creates a checkpoint and provides a channel to write to it. |
| * The name/location of the checkpoint are unknown to the user as of this time, in fact, |
| * the CheckpointID is not released to the user until {@link #commit(CheckpointWriteChannel) commit} is called. |
| * This makes enforcing atomicity of writes easy. |
| * |
| * @return a CheckpointWriteChannel that can be used to write to the checkpoint |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| CheckpointWriteChannel create() throws IOException, InterruptedException; |
| |
| /** |
| * Closes an existing checkpoint for writes and returns the CheckpointID that can be later |
| * used to get the read-only access to this checkpoint. |
| * |
| * Implementation is supposed to return the CheckpointID to the caller only on the |
| * successful completion of checkpoint to guarantee atomicity of the checkpoint. |
| * |
| * @param channel the CheckpointWriteChannel to commit |
| * @return a CheckpointID |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| CheckpointID commit(CheckpointWriteChannel channel) throws IOException, InterruptedException; |
| |
| /** |
| * Aborts the current checkpoint. Garbage collection choices are |
| * left to the implementation. The CheckpointID is neither generated nor released to the |
| * client so the checkpoint is not accessible. |
| * |
| * @param channel the CheckpointWriteChannel to abort |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| void abort(CheckpointWriteChannel channel) throws IOException, InterruptedException; |
| |
| /** |
| * Returns a reading channel to a checkpoint identified by the CheckpointID. |
| * |
| * @param checkpointId CheckpointID for the checkpoint to be opened |
| * @return a CheckpointReadChannel |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| CheckpointReadChannel open(CheckpointID checkpointId) throws IOException, InterruptedException; |
| |
| /** |
| * Discards an existing checkpoint identified by its CheckpointID. |
| * |
| * @param checkpointId CheckpointID for the checkpoint to be deleted |
| * @return a boolean confirming success of the deletion |
| * @throws IOException |
| * @throws InterruptedException |
| */ |
| boolean delete(CheckpointID checkpointId) throws IOException, InterruptedException; |
| |
| /** |
| * A channel to write to a checkpoint. |
| */ |
| interface CheckpointWriteChannel extends WritableByteChannel { |
| } |
| |
| /** |
| * A channel to read from a checkpoint. |
| */ |
| interface CheckpointReadChannel extends ReadableByteChannel { |
| } |
| } |